Sex differences in the prognostic significance of KRAS codons 12 and 13, and BRAF mutations in colorectal cancer: a cohort study

Background

Activating KRAS and BRAF mutations predict unresponsiveness to EGFR-targeting therapies in colorectal cancer (CRC), but their prognostic value needs further validation. In this study, we investigated the impact of KRAS codons 12 and 13, and BRAF mutations on survival from CRC, overall and stratified by sex, in a large prospective cohort study.

Methods

KRAS codons 12 and 13, and BRAF mutations were analysed by pyrosequencing of tumours from 525 and 524 incident CRC cases in The Malmö Diet and Cancer Study. Associations with cancer-specific survival (CSS) were explored by Cox proportional hazards regression, unadjusted and adjusted for age, TNM stage, differentiation grade, vascular invasion and microsatellite instability (MSI) status.

Results

KRAS and BRAF mutations were mutually exclusive. KRAS mutations were found in 191/ 525 (36.4%) cases, 82.2% of these mutations were in codon 12, 17.3% were in codon 13, and 0.5% cases had mutations in both codons. BRAF mutations were found in 78/524 (14.9%) cases. Overall, mutation in KRAS codon 13, but not codon 12, was associated with a significantly reduced CSS in unadjusted, but not in adjusted analysis, and BRAF mutation did not significantly affect survival. However, in microsatellite stable (MSS), but not in MSI tumours, an adverse prognostic impact of BRAF mutation was observed in unadjusted, but not in adjusted analysis. While KRAS mutation status was not significantly associated with sex, BRAF mutations were more common in women. BRAF mutation was not prognostic in women; but in men, BRAF mutation was associated with a significantly reduced CSS in overall adjusted analysis (HR = 3.50; 95% CI = 1.41–8.70), but not in unadjusted analysis. In men with MSS tumours, BRAF mutation was an independent factor of poor prognosis (HR = 4.91; 95% CI = 1.99–12.12). KRAS codon 13 mutation was associated with a significantly reduced CSS in women, but not in men in unadjusted, but not in adjusted analysis.

Conclusions

Results from this cohort study demonstrate sex-related differences in the prognostic value of BRAF mutations in colorectal cancer, being particularly evident in men. These findings are novel and merit further validation.

     

Expression of a mutant HSP110 sensitizes colorectal cancer cells to chemotherapy and improves disease prognosis

Heat shock proteins (HSPs) are necessary for cancer cell survival. We identified a mutant of HSP110 (HSP110ΔE9) in colorectal cancer showing microsatellite instability (MSI CRC), generated from an aberrantly spliced mRNA and lacking the HSP110 substrate-binding domain. This mutant was expressed at variable levels in almost all MSI CRC cell lines and primary tumors tested. HSP110ΔE9 impaired both the normal cellular localization of HSP110 and its interaction with other HSPs, thus abrogating the chaperone activity and antiapoptotic function of HSP110 in a dominant-negative manner. HSP110ΔE9 overexpression caused the sensitization of cells to anticancer agents such as oxaliplatin and 5-fluorouracil, which are routinely prescribed in the adjuvant treatment of people with CRC. The survival and response to chemotherapy of subjects with MSI CRCs was associated with the tumor expression level of HSP110ΔE9. HSP110 may thus constitute a major determinant for both prognosis and treatment response in CRC.     

结直肠腺瘤的微卫星不稳定状态与相关基因表达的研究

应用微切割-聚合酶链反应-单链长度多态性（PCR-SSLP）的方法,检测59例62个结直肠腺瘤,包括散发性腺瘤及家族性腺瘤性息肉病（FAP）腺瘤在BAT26等16个微卫星基因座在结直肠腺瘤标本的微卫星不稳定性（MSI）状态;并应用免疫组织化学SP法检测β-连接素（β-catenin）、TP53、BAX等的表达情况,初步探讨错配修复（MMR）基因在结直肠癌发生的早期即腺瘤阶段的作用及其意义。结果显示：(1)腺瘤16个基因座的总MSI发生率为14.4%;同一病人的不同腺瘤在某些相同的基因座表现出不同的MSI状态;(2)5例FAP病人均表现为MSI-L,其中有3例在hMSH3基因座表现为MSI阳性;(3)β-连接素在腺瘤和腺癌细胞膜阳性率分别为42.9%和11.4%,表达差异有显著统计学意义（P＜0.001）;(4)TP53、D5S346、TCF4(A)9、TGFβRⅡ(GT)3、TGFβRⅡ(A)10等微卫星基因座的MSI改变与相应的免疫组织化学指标TP53、β-连接素、TGFβRⅡ等在腺瘤及腺癌中的阳性表达有密切关系。可以推断：(1)在结直肠癌发生发展的早期即腺瘤阶段即可表现微卫星不稳定性,腺瘤中存在1p染色体的改变、APC基因的改变及TGFβ信号转导途径的异常;(2)随着腺瘤向腺癌的进展,β-连接素的阳性着色由细胞膜转移至细胞内,而且胞浆阳性强度增加;可以推断腺瘤中APC-β-联蛋白-TCF4信号转导途径的异常。 Abstract:In order to understand the role of mismatch repair (MMR) gene in colorectal carcinogenesis,microsatellite instability (MSI) status of 16 microsatellite loci of 62 adenomas from 59 patients,including sporadic and familial adeonmatous polyposis (FAP) adenomas were detected by microdissection-PCR-SSLP,and protein expressions of β -catenin,P53,and BAX,etc.were assayed by immunohistochemistry.Results were as following:(1)The overall MSI alteration rate of the 16 loci was 14.4%.Different adenomas from the same patient showed different microsatellite alterations at the same loci;(2)All of the five FAP patients were MSI-L,three of which showed MSI at the locus of hMSH3;(3)The membrane expression rate of β-catenin in adenomas and accompanied carcinomas was 42.9% and 11.4%,respectively (P＜0.001);⑷Microsatellite alterations of the microsatellite loci of TP53,D5S346,TCF4(A)9,TGFβRⅡ(GT)3 and TGFβRⅡ(A)10 were associated with the changes of their protein expressions.It could be concluded the following:(1)Microsatellite instability existed even in the early stage (adenomas) of colorectal tumorigenesis.The alterations of chromosome 1p,APC genes,and the TGFβ signal transduction pathway could also be deduced;(2)In the progression of adenoma to carcinoma,the staining of β-catenin would be transferred from membrane to cytoplasm and then nucleus,and the cytoplasm stain was stronger in carcinoma than that in adenomas.The abnormality of the signal transduction pathway of APC-β-catenin-TCF4 could be concluded.     

Overexpression of BIRC6 Is a Predictor of Prognosis for Colorectal Cancer

MethodsWe used Western blotting and immunohistochemistry to examine BIRC6 expression in 7 CRC cell lines and 126 CRC clinical samples. We determined the biological significance of BIRC6 in CRC cell lines by a lentivirus-mediated silencing method.ResultsWe reported that BIRC6 was overexpressed in CRC cell lines and clinical CRC tissues. BIRC6 overexpression was correlated with tumor size and invasion depth of CRC. BIRC6 overexpression is associated with worse overall survival (OS) (P = 0.001) and shorter disease-free survival (DFS) (P = 0.010). BIRC6 knockdown inhibited cell proliferation, arrested cell cycle at S phase, downregulated cyclin A2, B1, D1 and E1 levels, and sensitized CRC cells to chemotherapy in vitro and in vivo.ConclusionsTaken together, these data suggests that BIRC6 overexpression is a predictor of poor prognosis in colorectal cancer and BIRC6 could be a potential target of CRC therapy.     

ZG16 regulates PD-L1 expression and promotes local immunity in colon cancer

CRC is a heterogeneous disease due to global molecular alterations, including mismatch-repair-deficient (dMMR) and microsatellite instability-high (MSI-H). Immunotherapy has achieved durable responses in a subset of patients with dMMR-MSI-H metastatic CRC. It has been showed that Loss of ZG16 is highly associated with colorectal cancer. However, whether ZG16 modulates tumor immunity in colorectal cancer is unclear. In this study, we demonstrated that the expression of ZG16 is associated with distant metastasis and lymphatic invasive in colorectal cancer. Besides, ZG16 is negatively correlated to PD-L1 expression in patient with CRC and overexpression of ZG16 blocks PD-L1 expression in colorectal cancer cells. In addition, overexpression of ZG16 promotes NK cells survival and proliferation, which is dependent on NKG2D expression. Our data demonstrate that ZG16 plays a role in modulation of immune response in colorectal cancer. The strong correlation between ZG16 and PD-L1 suggests that ZG16 may serve a biomarker to stratify patient who will benefit from immunotherapy.     

Elevated MicroRNA-31 Expression Regulates Colorectal Cancer Progression by Repressing Its Target Gene SATB2

Several studies have brought about increasing evidence to support the hypothesis that miRNAs play a pivotal role in multiple processes of carcinogenesis, including cell growth, apoptosis, differentiation, and metastasis. In this study, we investigated the potential role of miR-31 in colorectal cancer (CRC) aggressiveness and its underlying mechanisms. We found that miR-31 increased in CRC cells originated from metastatic foci and human primary CRC tissues with lymph node metastases. Furthermore, the high-level expression of miR-31 was significantly associated with a more aggressive and poor prognostic phenotype of patients with CRC (p < 0.05). The stable over-expression of miR-31 in CRC cells was sufficient to promote cell proliferation, invasion, and migration in vitro. It facilitated tumor growth and metastasis in vivo too. Further studies showed that miR-31 can directly bind to the 3’untranslated region (3’UTR) of SATB2 mRNA and subsequently repress both the mRNA and protein expressions of SATB2. Ectopic expression of SATB2 by transiently transfected with pCAG-SATB2 vector encoding the entire SATB2 coding sequence could reverse the effects of miR-31 on CRC tumorigenesis and progression. In addition, ectopic over-expression of miR-31 in CRC cells induced epithelial-mesenchymal transition (EMT). Our results illustrated that the up-regulation of miR-31 played an important role in CRC cell proliferation, invasion, and metastasis in vitro and in vivo through direct repressing SATB2, suggesting a potential application of miR-31 in prognosis prediction and therapeutic application in CRC.     

Clinical impact of HLA class I expression in rectal cancer

Purpose To determine the clinical impact of human leukocyte antigen (HLA) class I expression in irradiated and non-irradiated rectal carcinomas. Experimental design Tumor samples in tissue micro array format were collected from 1,135 patients. HLA class I expression was assessed after immunohistochemical staining with two antibodies (HCA2 and HC10). Results Tumors were split into two groups: (1) tumors with >50% of tumor cells expressing HLA class I (high) and (2) tumors with ≤50% of tumor cells expressing HLA class I (low). No difference in distribution or prognosis of HLA class I expression was found between irradiated and non-irradiated patients. Patients with low expression of HLA class I (15% of all patients) showed an independent significantly worse prognosis with regard to overall survival and disease-free survival. HLA class I expression had no effect on cancer-specific survival or recurrence-free survival. Conclusions Down-regulation of HLA class I in rectal cancer is associated with poor prognosis. In contrast to our results, previous reports on HLA class I expression in colorectal cancer described a large population of patients with HLA class I negative tumors, having a good prognosis. This difference might be explained by the fact that a large proportion of HLA negative colon tumors are microsatellite instable (MSI). MSI tumors are associated with a better prognosis than microsatellite stable (MSS). As rectal tumors are mainly MSS, our results suggest that it is both, oncogenic pathway and HLA class I expression, that dictates patient’s prognosis in colorectal cancer. Therefore, to prevent confounding in future prognostic analysis on the impact of HLA expression in colorectal tumors, separate analysis of MSI and MSS tumors should be performed. Frank M. Speetjens and Elza C. de Bruin contributed equally to this work. Cornelis J.H. van de Velde is the Chairperson of the Total Mesorectal Excision Trial.     

Molecular genetic analysis of 103 sporadic colorectal tumours in Czech patients

The Czech Republic has one of the highest incidences of colorectal cancer (CRC) in Europe. To evaluate whether sporadic CRCs in Czech patients have specific mutational profiles we analysed somatic genetic changes in known CRC genes (APC, KRAS, TP53, CTNNB1, MUTYH and BRAF, loss of heterozygosity (LOH) at the APC locus, microsatellite instability (MSI), and methylation of the MLH1 promoter) in 103 tumours from 102 individuals. The most frequently mutated gene was APC (68.9% of tumours), followed by KRAS (31.1%), TP53 (27.2%), BRAF (8.7%) and CTNNB1 (1.9%). Heterozygous germline MUTYH mutations in 2 patients were unlikely to contribute to the development of their CRCs. LOH at the APC locus was found in 34.3% of tumours, MSI in 24.3% and MLH1 methylation in 12.7%. Seven tumours (6.9%) were without any changes in the genes tested. The analysis yielded several findings possibly specific for the Czech cohort. Somatic APC mutations did not cluster in the mutation cluster region (MCR). Tumours with MSI but no MLH1 methylation showed earlier onset and more severe mutational profiles compared to MSI tumours with MLH1 methylation. TP53 mutations were predominantly located outside the hot spots, and transitions were underrepresented. Our analysis supports the observation that germline MUTYH mutations are rare in Czech individuals with sporadic CRCs. Our findings suggest the influence of specific ethnic genetic factors and/or lifestyle and dietary habits typical for the Czech population on the development of these cancers.     

Microsatellite instability typing in serum and tissue of patients with colorectal cancer: comparing real time PCR with hybridization probe and high-performance liquid chromatography

Allelic variation of BAT-25 (a 25-repeat quasimonomorphic poly T) and BAT-26 (a 26-repeat quasimonomorphic polyA) loci as two mononucleotide microsatellite markers, were analyzed with high-performance liquid chromatography (HPLC) compared with Real-Time PCR using hybridization probes. BAT-26 and BAT-25 markers were used to determine an appropriate screening technique with high sensitivity and specificity to diagnose microsatellite instability (MSI) status in patients with colorectal cancer (CRC). One of the pathways in colorectal tumor genesis is microsatellite instability (MSI⁺). MSI is detected in about 15 % of all CRCs; 3 % are of these are associated with Lynch syndrome and the other 12 % are caused by sporadic. Colorectal tumors with MSI have distinctive features compared with microsatellite stable tumors. Due to the high percentage of MSI⁺ CRC in Iran, screening of this type of CRC is imperative. Two markers were analyzed in tissues and sera of 44 normal volunteers and tumor and matched normal mucosal tissues as well as sera of 44 patients with sporadic CRC. The sensitivity and specificity of BAT-26 with real time PCR method (Hybridization probe) were 100 % in comparison with sequencing method as the gold standard, while HPLC had a lower sensitivity and specificity. According to HPLC data, BAT-26 was more sensitive than BAT-25 in identifying MSI tumors. Therefore, MSI typing using the BAT-26 hybridization probe method compared to HPLC could be considered as an accurate method for diagnosing MSI in CRC tumors but not in serum circulating DNAs.     

Src family kinases,HCK and FGR,associate with local inflammation and tumour progression in colorectal cancer

BackgroundIn colorectal cancer (CRC), inflammatory responses have been reported to associate with patient survival. However, the specific signalling pathways responsible for regulating inflammatory responses are not clear. Src family kinases (SFKs) impact tumourigenic processes, including inflammation.MethodsThe relationship between SFK expression, inflammatory responses and cancer specific survival (CSS) in stage I-III CRC patients was assessed using immunohistochemistry on a 272 patient discovery cohort and an extended 822 patient validation cohort.ResultsIn the discovery cohort, cytoplasmic FGR associated with improved CSS (P = 0.019), with membrane HCK (p = 0.093) trending towards poorer CSS. In the validation cohort membrane FGR (p = 0.016), membrane HCK (p = 0.019), and cytoplasmic HCK (p = 0.030) all associated with poorer CSS. Both markers also associated with decreased proliferation and cytotoxic T-lymphocytes (all p < 0.05). Furthermore, cytoplasmic HCK was an independent prognostic marker compared to common clinical factors. To assess synergy a combine FGR + HCK score was assessed. The membrane FGR + HCK score strengthened associations with poor prognosis (p = 0.006), decreased proliferation (p < 0.001) and cytotoxic T-lymphocytes (p < 0.001).ConclusionsSFKs associate with prognosis and the local inflammatory response in patients with stage I-III CRC. Active membrane FGR and HCK work in parallel to promote tumour progression and down-regulation of the local inflammatory lymphocytic response.     

Nonsense-mediated mRNA decay impacts MSI-driven carcinogenesis and anti-tumor immunity in colorectal cancers

Nonsense-mediated mRNA Decay (NMD) degrades mutant mRNAs containing premature termination codon (PTC-mRNAs). Here we evaluate the consequence of NMD activity in colorectal cancers (CRCs) showing microsatellite instability (MSI) whose progression is associated with the accumulation of PTC-mRNAs encoding immunogenic proteins due to frameshift mutations in coding repeat sequences. Inhibition of UPF1, one of the major NMD factors, was achieved by siRNA in the HCT116 MSI CRC cell line and the resulting changes in gene expression were studied using expression microarrays. The impact of NMD activity was also investigated in primary MSI CRCs by quantifying the expression of several mRNAs relative to their mutational status and to endogenous UPF1 and UPF2 expression. Host immunity developed against MSI cancer cells was appreciated by quantifying the number of CD3epsilon-positive tumor-infiltrating lymphocytes (TILs). UPF1 silencing led to the up-regulation of 1251 genes in HCT116, among which a proportion of them (i.e. 38%) significantly higher than expected by chance contained a coding microsatellite (P<2x10(-16)). In MSI primary CRCs, UPF1 was significantly over-expressed compared to normal adjacent mucosa (P<0.002). Our data provided evidence for differential decay of PTC-mRNAs compared to wild-type that was positively correlated to UPF1 endogenous expression level (P = 0.02). A negative effect of UPF1 and UPF2 expression on the host's anti-tumor response was observed (P<0.01). Overall, our results show that NMD deeply influences MSI-driven tumorigenesis at the molecular level and indicate a functional negative impact of this system on anti-tumor immunity whose intensity has been recurrently shown to be an independent factor of favorable outcome in CRCs.     

Two modes of microsatellite instability in human cancer: differential connection of defective DNA mismatch repair to dinucleotide repeat instability

Microsatellite instability (MSI) is associated with defective DNA mismatch repair in various human malignancies. Using a unique fluorescent technique, we have observed two distinct modes of dinucleotide microsatellite alterations in human colorectal cancer. Type A alterations are defined as length changes of ≤6 bp. Type B changes are more drastic and involve modifications of ≥8 bp. We show here that defective mismatch repair is necessary and sufficient for Type A changes. These changes were observed in cell lines and in tumours from mismatch repair gene-knockout mice. No Type B instability was seen in these cells or tumours. In a panel of human colorectal tumours, both Type A MSI and Type B instability were observed. Both types of MSI were associated with hMSH2 or hMLH1 mismatch repair gene alterations. Intriguingly, p53 mutations, which are generally regarded as uncommon in human tumours of the MSI⁺ phenotype, were frequently associated with Type A instability, whereas none was found in tumours with Type B instability, reflecting the prevailing viewpoint. Inspection of published data reveals that the microsatellite instability that has been observed in various malignancies, including those associated with Hereditary Non-Polyposis Colorectal Cancer (HNPCC), is predominantly Type B. Our findings indicate that Type B instability is not a simple reflection of a repair defect. We suggest that there are at least two qualitatively distinct modes of dinucleotide MSI in human colorectal cancer, and that different molecular mechanisms may underlie these modes of MSI. The relationship between MSI and defective mismatch repair may be more complex than hitherto suspected.     

High density of tryptase‐positive mast cells in human colorectal cancer: a poor prognostic factor related to protease‐activated receptor 2 expression

Tryptase(+) mast cells (MCs), abundant in the invasive front of tumours, contribute to tissue remodelling. Indeed, protease‐activated receptor‐2 (PAR‐2) activation by MC‐tryptase is considered an oncogenic event in colorectal cancer (CRC). Recently, we have suggested NHERF1 as a potential new marker in CRC. In this study, we aimed to determine the distribution of tryptase(+) MCs and PAR‐2 and to examine the relationship between PAR‐2 and NHERF1, investigating their reputed usefulness as tumour markers. We studied a cohort of 115 CRC specimens including primary cancer (C) and adjacent normal mucosa (NM) by immunohistochemical double staining, analyzing the protein expression of MC‐tryptase, PAR‐2 and cytoplasmic NHERF1. MC density was higher in NM than in C. Tumours with high TNM stage and poor grade showed the highest MC density. A higher PAR‐2 immunoreactivity characterized tumours most infiltrated by MCs compared with samples with low MC density. Furthermore, PAR‐2 overexpression was associated with advanced TNM stage, poor grade and lymphovascular invasion (LVI). A positive correlation existed between tryptase(+) MC density and PAR‐2 expression. Cytoplasmic NHERF1 was higher in C than in NM and overexpressing tumours resulted associated with nodal and distant metastases, poor grade and LVI. PAR‐2 correlated with cytoplasmic NHERF1 and the PAR‐2(+)/cytoplasmic NHERF1(+) expression immunophenotype identified tumours associated with unfavourable prognosis and aggressive clinical parameters. Our data indicate that the high density of tryptase(+) MCs at invasive margins of tumours was associated with advanced stages of CRC and was strongly correlated with PAR‐2 expression.     

A pilot study on clinicopathological features and intestinal microflora changes in colorectal cancer patients born over a nine-year period encompassing three years before and after the Great Chinese famine

BackgroundExposure to energy restriction during childhood is associated with a lower risk of developing colorectal cancer (CRC). To date, the association between this critical period of growth and prognosis of CRC has rarely been investigated. Changes in microbiota and epigenetic dysregulation may be key underlying mechanisms.MethodologyTissues collected from patients born between 1956 and 1964 were grouped based on time-period. The differences in overall survival among patients from the three time-periods were examined via univariate analysis. The 16S rRNA gene sequencing approach was to determine differences in microbiota among the groups. Samples were randomly selected to detect BRAF mutations, microsatellite instability (MSI) and promoter CpG island methylator phenotype (CIMP) status. The chi-square test was to assess the relationship between alterations in these molecules and microbiota differences.ResultsPatients from the three groups differed in terms of location of CRC (P = 0.034) and carcinoembryonic antigen (CEA) level (P = 0.036). A survival advantage was observed in the famine group compared with the other two groups. Fusobacterium nucleatum, Bacteroides fragilis and Escherichia coli were more abundant in the two comparing groups. Abundance of B. fragilis was associated with BRAF mutations, microsatellite instability (MSI) and abundance of E. coli. Moreover, the incidence of CIMP and MSI was higher in patients with greater abundance of F. nucleatum.ConclusionsLimitation of energy intake during childhood may affect the composition of gut microbiota, resulting in persistent epigenetic changes that subsequently influence the prognosis of patients with CRC.     

Treatment with the PARP inhibitor,niraparib, sensitizes colorectal cancer cell lines to irinotecan regardless of MSI/MSS status

Background

Cells with homologous recombination (HR) deficiency, most notably caused by mutations in the BRCA1 or BRCA2 genes, are sensitive to PARP inhibition. Microsatellite instability (MSI) accounts for 10-15% of colorectal cancer (CRC) and is hypothesized to lead to HR defects due to altered expression of Mre11, a protein required for double strand break (DSB) repair. Indeed, others have reported that PARP inhibition is efficacious in MSI CRC.

Methods

Here we examine the response to niraparib, a potent PARP-1/PARP-2 inhibitor currently under clinical evaluation, in MSI versus microsatellite stable (MSS) CRC cell lines in vitro and in vivo. We compiled a large panel of MSI and MSS CRC cell lines and evaluated the anti-proliferative activity of niraparib. In addition to testing single agent cytotoxic activity of niraparib, we also tested irinotecan (or SN-38, the active metabolite of irinotecan) activity alone and in combination with niraparib in vitro and in vivo.

Results

In contrast to earlier reports, MSI CRC cell lines were not more sensitive to niraparib than MSS CRC cell lines¸ suggesting that the MSI phenotype does not sensitize CRC cell lines to PARP inhibition. Moreover, even the most sensitive MSI cell lines had niraparib EC50s greater than 10 fold higher than BRCA-deficient cell lines. However, MSI lines were more sensitive to SN-38 than MSS lines, consistent with previous findings. We have also demonstrated that combination of niraparib and irinotecan was more efficacious than either agent alone in both MSI and MSS cell lines both in vitro and in vivo, and that niraparib potentiates the effect of irinotecan regardless of MSI status.

Conclusions

Our results support the clinical evaluation of this combination in all CRC patients, regardless of MSI status.     

Relationships between p14ARF Gene Methylation and Clinicopathological Features of Colorectal Cancer: A Meta-Analysis

We conducted a meta-analysis to explore the relationships between p14^ARF gene methylation and clinicopathological features of colorectal cancer (CRC). Databases, including Pubmed, Embase and Cochrane Library, were searched and, finally, a total of 18 eligible researches encompassing 1988 CRC patients were selected. Combined odds ratios (ORs) with 95% confidence intervals (95% CIs) were evaluated under a fixed effects model for absence of heterogeneity. Significant associations were observed between p14^ARF gene methylation and tumor location (OR = 2.35, 95% CI: 1.55–3.55, P = 0.001), microsatellite instability (MSI) status (OR = 3.28, 95% CI: 2.12–5.07, P<0.0001). However, there were no significant associations between p14^ARF gene methylation and tumor stage, tumor differentiation. We concluded that p14^ARF gene methylation may be significantly associated with tumor location, and MSI status of CRC.     

Distinct molecular features of colorectal cancer in Ghana

Objectives: While colorectal cancer (CRC) is common, its incidence significantly varies around the globe. The incidence of CRC in West Africa is relatively low, but it has a distinctive clinical pattern and its molecular characteristics have not been studied. This study is one of the first attempts to analyze molecular, genetic, and pathological characteristics of colorectal cancer in Ghana. Methods: DNA was extracted from microdissected tumor and adjacent normal tissue of 90 paraffin blocks of CRC cases (1997–2007) collected at the University of Ghana. Microsatellite instability (MSI) was determined using fragment analysis of ten microsatellite markers. We analyzed expression of mismatch repair (MMR) proteins by immunohistochemistry and sequenced exons 2 and 3 of KRAS and exon 15 of BRAF. Results: MSI analysis showed 41% (29/70) MSI-High, 20% (14/70) MSI-Low, and 39% (27/70) microsatellite-stable (MSS) tumors. Sequencing of KRAS exons 2 and 3 identified activating mutations in 32% (24/75) of tumors, and sequencing of BRAF exon 15, the location of the common activating mutation (V600), did not show mutations at codons 599 and 600 in 88 tumors. Conclusions: Our study found a high frequency of MSI-High colorectal tumors (41%) in Ghana. While the frequency of KRAS mutations is comparable with other populations, absence of BRAF mutations is intriguing and would require further analysis of the molecular epidemiology of CRC in West Africa.     

Anti-PD-1 combined with targeted therapy: Theory and practice in gastric and colorectal cancer

Gastric cancer (GC) and colorectal cancer (CRC) are frequent and aggressive malignancies worldwide. Despite the emergence of various therapeutic regimens, the prognosis of gastric and colorectal cancer is relatively poor. Immunotherapy targeting PD-1 is one of the most prevalent approaches, but it has a low response rate in most patients, particularly those with microsatellite stability (MSS). Recently, some targeted drugs have been found to remarkably enhance the anti-tumor immunity of cancer models, mainly through increasing the level of CD8⁺ T cells, M1-type macrophages, expression of PD-L1, and decreasing the level of regulatory T cells and M2 macrophages. The above finding implies that the combination of anti-PD-1 and targeted therapies may be a potential treatment for gastric and colorectal cancer patients. Although many encouraging preclinical results have been shown, the clinical outcomes were not approving enough. To further enhance the therapeutic efficacy and improve the prognosis in GC and CRC patients, deeper and larger-scale studies should be done to determine the complicated interactions between the two therapies and the concrete use of combination regimens.     

SATB1 Expression Is Associated with Biologic Behavior in Colorectal Carcinoma In Vitro and In Vivo

There is increasing evidence that Special AT-rich sequence-binding protein 1 (SATB1) is aberrantly expressed in several cancers and is correlated with clinicopathologic parameters in these tumors. In this study, we showed over-expression of SATB1 in 80 cases of colorectal cancer and in 3 colorectal cancer cell lines and found expression levels were strongly associated with tumor differentiation and stage. Expression levels of SATB1 protein were higher in poorly-differentiated as compared with well-differentiated cell lines, and both quantity and distribution patterns of SATB1 were associated with tumor differentiation and pTNM stage. Strikingly, we further investigated the effect of down regulation of SATB1 expression on malignant phenotypic features in colorectal cancer cells in vitro, and showed that SABT1 down-regulation negatively affected growth potential, anchorage-independent colony formation and cancer cell invasion, and resulted in increased apoptosis. SATB1 expression was positively associated with the expression of various biological and genetic markers, including Cyclin D1, MMP-2, NF-κB, and PCNA, and was associated with loss of APC and BRAF^V600E. These findings suggest that SATB1 is involved in the carcinogenesis, development and progression of colorectal cancer.     

DNA methylation-mediated repression of miR-181a/135a/302c expression promotes the microsatellite-unstable colorectal cancer development and 5-FU resistance via targeting PLAG1

Microsatellite instability (MSI) defines a subtype of colorectal cancer (CRC) with typical clinicopathologic characteristics. CRCs with MSI (MSI CRCs) frequently acquire accelerated carcinogenesis and 5-FU resistance, and the exact underlying mechanism remains incompletely understood. Our previous study has identified the microRNA (miRNA) expression profile in MSI CRCs. In this study, three miRNAs (miR-181a, miR-135a and miR-302c) were validated by qRT-PCR to be dramatically decreased in 67 CRC samples. Proliferation and apoptosis assays demonstrated that miR-181a/135a/302c function as tumor suppressors via repressing PLAG1/IGF2 signaling. Moreover, we presented compelling evidence that restoration of miR-181a/135a/302c expression promoted sensitivity of MSI CRC cells to 5-FU treatment. miR-181a/135a/302c exerted their effect on chemoresistance through attenuating PLAG1 expression. Notably, the hypermethylation status of MSI CRC accounts for the decrements of miR-181a/135a/302c. Our results contribute to a better understanding of the mechanism of chemoresistance in MSI CRCs, and provide a clue for digging the biomarkers and therapeutic targets for CRC patients.