Depolarization recruits DCC to the plasma membrane of embryonic cortical neurons and enhances axon extension in response to netrin-1

The netrin-1 receptor Deleted in Colorectal Cancer (DCC) is required for the formation of major axonal projections by embryonic cortical neurons, including the corpus callosum, hippocampal commissure, and cortico-thalamic tracts. The presentation of DCC by axonal growth cones is tightly regulated, but the mechanisms regulating DCC trafficking within neurons are not well understood. Here, we investigated the mechanisms regulating DCC recruitment to the plasma membrane of embryonic cortical neurons. In embryonic spinal commissural neurons, protein kinase A (PKA) activation recruits DCC to the plasma membrane and enhances axon chemoattraction to netrin-1. We demonstrate that PKA activation similarly recruits DCC and increases embryonic cortical neuron axon extension, which, like spinal commissural neurons, respond to netrin-1 as a chemoattractant. We then determined if depolarization might recruit DCC to the plasma membrane. Neither netrin-1 induced axon extension, nor levels of plasma membrane DCC, were altered by depolarizing embryonic spinal commissural neurons with elevated levels of KCl. In contrast, depolarizing embryonic cortical neurons increased the amount of plasma membrane DCC, including at the growth cone, and increased axon outgrowth evoked by netrin-1. Inhibition of PKA, phosphatidylinositol-3-kinase, protein kinase C, or exocytosis blocked the depolarization-induced recruitment of DCC and suppressed axon outgrowth. Inhibiting protein synthesis did not affect DCC recruitment, nor were the distributions of trkB or neural cell adhesion molecule (NCAM) influenced by depolarization, consistent with selective mobilization of DCC. These findings identify a role for membrane depolarization modulating the response of axons to netrin-1 by regulating DCC recruitment to the plasma membrane.     

DCC (deleted in colorectal carcinoma) gene variants confer increased susceptibility to gallbladder cancer (Ref. No.: Gene-D-12-01446)

Background and aim

GBC is a lethal and multifaceted disease. Deleted in colorectal carcinoma (DCC) is a well known tumor suppressor gene. Recently a small genome-wide association study (GWAS) identified DCC to be significantly associated with gallbladder cancer (GBC) susceptibility in a Japanese population sample. However, the study sample size was small and lacked independent replication. Therefore, the present study was carried out to replicate the association of two GWAS identified DCC SNPs (A>G_rs4078288, C>T_rs7504990) and two other SNPs (C>G_rs2229080 and A>G_rs714) previously associated with various cancers.

Methodology

The study was accomplished in 406 GBC cases and 260 healthy control samples from North India. Genotyping was carried out by PCR-RFLP and Taqman genotyping assays. Statistical analysis was performed by using SPSS ver16 and functional prediction of these variants was carried out using Bioinformatics tools (FAST-SNP, F-SNP).

Result

We did not observe association with GWAS-identified SNPs of DCC but other SNPs showed significant association. In addition, a DCC haplotype G_rs2229080-A_rs4078288-C_rs7504990-A_rs714 conferred high risk of GBC in India. The haplotype associated risk was independent of gallstone, sex or tobacco usages which are well-known modifiers of GBC risk. Further analysis suggested DCC A>G_rs714 as a major risk conferring SNP in the Indian population.

Conclusion

This study re-affirms the role of plausible tumor suppressor DCC variants, in gallbladder carcinogenesis and the risk haplotype may be explored as a useful marker for GBC susceptibility.     

Expression of Duffy antigen receptor for chemokines (DARC) is down-regulated in colorectal cancer

Abstract

Duffy antigen receptor for chemokines (DARC) is a silent chemokine receptor which selectively binds angiogenic chemokines without inducing conventional signaling responses. DARC has been reported to inhibit the development of multiple cancers through clearance of angiogenic chemokines. However, its role in colorectal cancer (CRC) remains unclear. We investigated the expression of DARC in CRC and explored correlation of DARC expression with clinical pathological features and microvessel density (MVD). The protein expression levels of DARC were detected by immunohistochemistry in 90 CRC and 64 paired unaffected tissues. The mRNA levels of DARC were detected by quantitative real-time PCR in 15 CRC and paired unaffected tissues. MVD in CRC was also assessed by immunohistochemistry of CD34. We found that the mRNA and protein expression levels of DARC were significantly lower in CRC than in the unaffected tissues (p?<?0.05). The DARC protein expression levels were positively correlated with DARC mRNA expression levels in both CRC (p?<?0.001) and unaffected tissues (p?<?0.001). We also found that DARC expression was significantly correlated with tumor differentiation (p?<?0.001), lymph node metastasis (p?<?0.01) and TNM stage (p?<?0.05). Moreover, we observed a strong negative relationship between DARC expression and MVD in CRC (p?<?0.001). We showed that DARC expression is down-regulated in CRC and associated with clinical pathological features and MVD of CRC. DARC might be involved in tumorigenesis, progression, angiogenesis, and metastasis of CRC.     

Solution structures, dynamics, and lipid-binding of the sterile alpha-motif domain of the deleted in liver cancer 2

The deleted in liver cancer 2 (DLC2) is a tumor suppressor gene, frequently found to be underexpressed in hepatocellular carcinoma. DLC2 is a multidomain protein containing a sterile alpha-motif (SAM) domain, a GTPase-activating protein (GAP) domain, and a lipid-binding StAR-related lipid-transfer (START) domain. The SAM domain of DLC2, DLC2-SAM, exhibits a low level of sequence homology (15-30%) with other SAM domains, and appears to be the prototype of a new subfamily of SAM domains found in DLC2-related proteins. In the present study, we have determined the three-dimensional solution structure of DLC2-SAM using NMR methods together with molecular dynamics simulated annealing. In addition, we performed a backbone dynamics study. The DLC2-SAM packed as a unique four alpha-helical bundle stabilized by interhelix hydrophobic interactions. The arrangement of the four helices is distinct from all other known SAM domains. In contrast to some members of the SAM domain family which form either dimers or oligomers, both biochemical analyses and rotational correlation time (tau(c)) measured by backbone 15N relaxation experiments indicated that DLC2-SAM exists as a monomer in solution. The interaction of DLC2-SAM domain with sodium dodecyl sulfate (SDS) micelles and 1,2-dimyristoyl-sn-glycerol-3-phosphatidylglycerol (DMPG) phospholipids was examined by CD and NMR spectroscopic techniques. The DLC2-SAM exhibits membrane binding properties accompanied by minor loss of the secondary structure of the protein. Deletion studies showed that the self-association of DLC2 in vivo does not require SAM domain, instead, a protein domain consisting of residues 120-672 mediates the self-association of DLC2.     

Identification and development of long non‐coding RNA‐associated regulatory network in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer‐associated death globally. Long non‐coding RNAs (lncRNAs) have been identified as micro RNA (miRNA) sponges in a competing endogenous RNA (ceRNA) network and are involved in the regulation of mRNA expression. This study aims to construct a lncRNA‐associated ceRNA network and investigate the prognostic biomarkers in CRC. A total of 38 differentially expressed (DE) lncRNAs, 23 DEmiRNAs and 27 DEmRNAs were identified by analysing the expression profiles of CRC obtained from The Cancer Genome Atlas (TCGA). These RNAs were chosen to develop a ceRNA regulatory network of CRC, which comprised 125 edges. Survival analysis showed that four lncRNAs, six miRNAs and five mRNAs were significantly associated with overall survival. A potential regulatory axis of ADAMTS9‐AS2/miR‐32/PHLPP2 was identified from the network. Experimental validation was performed using clinical samples by quantitative real‐time PCR (qRT‐PCR), which showed that expression of the genes in the axis was associated with clinicopathological features and the correlation among them perfectly conformed to the ‘ceRNA theory’. Overexpression of ADAMTS9‐AS2 in colon cancer cell lines significantly inhibited the miR‐32 expression and promoted PHLPP2 expression, while ADAMTS9‐AS2 knockdown had the opposite effects. The constructed novel ceRNA network may provide a comprehensive understanding of the mechanisms of CRC carcinogenesis. The ADAMTS9‐AS2/miR‐32/PHLPP2 regulatory axis may serve as a potential therapeutic target for CRC.     

The positive impact of cytological specimens for EGFR mutation testing in non‐small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases

B. Pang, D. Matthias, C.W. Ong, A.N. Dhewar, S. Gupta, G.L. Lim, M.‐E. Nga, J.E. Seet, A. Qasim, T.‐M. Chin, R. Soo, R. Soong and M. Salto‐Tellez The positive impact of cytological specimens for EGFR mutation testing in non‐small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases Objectives: To compare the rejection rates of non‐small cell lung cancer (NSCLC) samples obtained by differing sampling methods for testing by Sanger sequencing for epidermal growth factor receptor (EGFR) mutations. To assess the association between unsatisfactory outcomes and the quantity of DNA extracted from cytological versus histological samples. Methods: Six hundred and seventy NSCLC samples referred to our centre from 2008 to 2010 were reviewed as a consequence of sample rejection, presence of EGFR mutations, cytological versus histological sampling methods, DNA quantity and the unsatisfactory genotyping rate. Results: Eighty samples were rejected for testing in similar proportions of histological and cytological samples (11.9% versus 10.9%) usually (n = 75) because the amount of cellular material was judged insufficient in small biopsies or cytology samples. The remaining 590 samples on which EGFR testing was attempted yielded 51 (8.6%) unsatisfactory test outcomes caused by failure of the polymerase chain reaction (PCR) (n = 47 cases), uninterpretable Sanger chromatograms (n = 3 cases) and insufficient DNA extracted for PCR (n = 1 case). The difference in rates of unsatisfactory outcomes between cytological samples (seven of 147 samples or 4.7%) versus tissue samples (44 of 443 samples or 9.9%) was clinically relevant but not statistically significant (Mann–Whitney test; P < 0.081). There was no association between the concentration of DNA extracted and the likelihood of an unsatisfactory analysis; which was similar in all types of sections (large and small) while 0% of 37 cytology slides were unsatisfactory. Conclusions: Utilizing cytology samples for EGFR testing avoids unnecessary patient re‐biopsing and yields a clinically superior satisfactory rate to the overall satisfactory rate of tissue biopsies of NSCLC. The quality rather than quantity of DNA extracted may be a more important determinant of a satisfactory result.     

The receptor protein tyrosine phosphatase (RPTP)beta/zeta is expressed in different subtypes of human breast cancer

Increasing evidence suggests mutations in human breast cancer cells that induce inappropriate expression of the 18-kDa cytokine pleiotrophin (PTN, Ptn) initiate progression of breast cancers to a more malignant phenotype. Pleiotrophin signals through inactivating its receptor, the receptor protein tyrosine phosphatase (RPTP)beta/zeta, leading to increased tyrosine phosphorylation of different substrate proteins of RPTPbeta/zeta, including beta-catenin, beta-adducin, Fyn, GIT1/Cat-1, and P190RhoGAP. PTN signaling thus has wide impact on different important cellular systems. Recently, PTN was found to activate anaplastic lymphoma kinase (ALK) through the PTN/RPTPbeta/zeta signaling pathway; this discovery potentially is very important, since constitutive ALK activity of nucleophosmin (NPM)-ALK fusion protein is causative of anaplastic large cell lymphomas, and, activated ALK is found in other malignant cancers. Recently ALK was identified in each of 63 human breast cancers from 22 subjects. We now demonstrate that RPTPbeta/zeta is expressed in each of these same 63 human breast cancers that previously were found to express ALK and in 10 additional samples of human breast cancer. RPTPbeta/zeta furthermore was localized not only in its normal association with the cell membrane but also scattered in cytoplasm and in nuclei in different breast cancer cells and, in the case of infiltrating ductal carcinomas, the distribution of RPTPbeta/zeta changes as the breast cancer become more malignant. The data suggest that the PTN/RPTPbeta/zeta signaling pathway may be constitutively activated and potentially function to constitutively activate ALK in human breast cancer.     

Deletion of theAlu-VpA/MycL1 (1p34.3) locus is a negative prognostic sign in human colorectal cancer

We examined deletions of the short arm of chromosome 1 and aberrations of the microsatellite locusAlu-VpA/MycL1 (1p34.3) in human primary colorectal adenocarcinomas. Cytogenetically discernible deletions in 1p were found in 45% (14/31) of informative tumors. The 1p-tumors commonly exhibited a polyploid karyotype (FisherP ₁=0.023) and a larger number of rearranged chromosomes (P ₂=0.045) versus those without 1p deletions. The 1p deletions often combined with chromosome 5 monosomy (χ²=6.24; p=0.013), chromosome 15 monosomy (χ²=4.20;p=0.040), and 11q deletions (P ₂=0.035). Among the 50 carcinomas, 11 (22%) showedAlu-VpA/MycL1 instability, and 14% (6/43 informative) had lost theAlu-VpA/MycL1 allele. The genetic alterations thus revealed were collated with the clinical and morphological features of the tumors. The loss of the 1p material was shown to be correlated with marked karyotype aberrations in colorectal tumors, andAlu-VpA/MycL1 allele deletions were tightly associated with relapses or metastasis within 30 months after surgery.     

KITLG is a novel target of miR‐34c that is associated with the inhibition of growth and invasion in colorectal cancer cells

MiR‐34c is considered a potent tumour suppressor because of its negative regulation of multiple target mRNAs that are critically associated with tumorigenesis and metastasis. In the present study, we demonstrated a novel target of miR‐34c, KITLG, which has been implicated in colorectal cancer (CRC). First, we found a significant negative relationship between miR‐34c and KITLG mRNA expression levels in CRC cell lines, including HT‐29, HCT‐116, SW480 and SW620 CRC cell lines. In silico analysis predicted putative binding sites for miR‐34c in the 3′ untranslated region (3′UTR) of KITLG mRNA. A dual‐luciferase reporter assay further confirmed that KITLG is a direct target of miR‐34c. Then, the cell lines were infected with lentiviruses expressing miR‐34c or a miR‐34c specific inhibitor. Restoration of miR‐34c dramatically reduced the expression of KITLG mRNA and protein, while silencing of endogenous miR‐34c increased the expression of KITLG protein. The miR‐34c‐mediated down‐regulation of KITLG was associated with the suppression on proliferation, cellular transformation, migration and invasion of CRC cells, as well as the promotion on apoptosis. Knockdown of KITLG by its specific siRNA confirmed a critical role of KITLG down‐regulation for the tumour‐suppressive effects of miR‐34c in CRC cells. In conclusion, our results demonstrated that miR‐34c might interfere with KITLG‐related CRC and could be a novel molecular target for CRC patients.     

A novel 5-Fluorocuracil multiple-nanoemulsion used for the enhancement of oral bioavailability in the treatment of colorectal cancer

5-Fluorouracil (5-FU) is a drug of choice for colorectal-cancer. But oral therapeutic efficacy of 5-FU is restricted due to their very little bioavailability because of poor membrane permeability and GIT-absorption. We have developed a multiple nanoemulsion (w/o/w i.e. 5-FU-MNE) in which 5-FU incorporated to improve their oral-absorption. Globule-size of opt-5-FU-MNE was 51.64 ± 2.61 nm with PDI and ZP 0.101 ± 0.001 and −5.59 ± 0.94, respectively. In vitro 5-FU-release and ex vivo permeation studies exhibited 99.71% release and 83.64% of 5-FU from opt-nanoformulation. Cytotoxic in vitro studies-exhibited that 5-FU in opt-5-FU-MNE was 5-times more potent than 5-FU-S on human-colon-cancer-cell-lines (HT-29). The enhanced C_max with AUC_0-8h with opt-5-FU-MNE was shown extremely significant (p < 0.001) in wistar rat’s plasma in the comparison of oral and i.v. treated group of 5-FU-S by PK-observations. Furthermore, opt-5-FU-MNE was showed much more significant (p < 0.001) results as compared to 5-FU-S (free) on cell lines for human colon cancer (HT-29).     

CrkI and p130(Cas) complex regulates the migration and invasion of prostate cancer cells

Prostate cancer metastasis is often associated with poor prognosis. The molecular coupling of the adaptor protein Crk to the docking protein p130(Cas) serves as a switch that regulates cell migration in several invasive cancer cells and Ack appears to act upstream of CrkII to modulate the cell motility. However, the precise role of Ack, Crk and p130(Cas) complex in prostate cancer migration remains unknown. In this study we examined the expression of Crk and p130(Cas) in prostate cancer cell lines, and found that CrkI and p130(Cas) protein level was higher in highly invasive PC-3M and PC-3 cell lines than in moderately invasive DU-145 cells. Upon shRNA mediated knockdown of CrkI and p130(Cas) in PC-3M cells, cell migration and invasion were significantly inhibited as analyzed by wound healing assay and transwell invasion assay. Furthermore, co-immunoprecipitation assay showed that p130(Cas) interacted with CrkI in PC-3M cells and the stability of p130(Cas) and CrkI depended on each other. AckI interacted with both CrkI and p130(Cas) and the interaction of AckI with CrkI seemed to be independent of p130(Cas) . Taken together, our results demonstrate the high expression of CrkI and p130(Cas) in invasive prostate cancer cells and the important role of CrkI/p130(Cas) complex in the migration and invasion of prostate cancer cells. These data suggest that CrkI/p130(Cas) could be exploited as potential molecular therapeutic target for prostate cancer metastasis.     

Phosphorylation of Dpsyl2 (CRMP2) and Dpsyl3 (CRMP4) is required for positioning of caudal primary motor neurons in the zebrafish spinal cord

Dpysls (CRMPs) that were initially identified as mediator proteins of Semaphorin3a (Sema3a) signaling are involved in neuronal polarity and axon elongation in cultured neurons. Previous studies have shown that knockdown of neuropilin1a, one of the sema3a receptors, exhibited ectopic primary motor neurons (PMNs) outside of the spinal cord in zebrafish. However, downstream molecules of sema3a signaling involved in the positioning of motor neurons are largely unknown. Here, we addressed the role of Dpysl2 (CRMP2) and Dpysl3 (CRMP4) in the positioning of PMNs in the zebrafish spinal cord. We found that the knockdown of dpysls by antisense morpholino oligonucleotides (AMO) causes abnormal positioning of caudal primary (CaP) motor neurons outside the spinal cord. The knockdown of cdk5 and dyrk2 by AMO also caused similar phenotype in the positioning of CaP motor neurons, and this phenotype was rescued by co‐injection of phosphorylation‐mimic type dpysl2 mRNA. These results suggest that the phosphorylation of Dpysl2 and Dpysl3 by Cdk5 and Dyrk2 is required for correct positioning of CaP motor neurons in the zebrafish spinal cord. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 73: 911–920, 2013     

Expression of the membrane complement regulatory protein CD59 (protectin) is associated with reduced survival in colorectal cancer patients

It has been known for some time that the immune system can recognise growing tumours, and that tumours may respond by modulation of molecules, which make them resistant to further attack. Expression, over-expression, or loss of these molecules may function as markers of tumour progression and prognosis. Among such molecules are the membrane-bound complement regulatory proteins (mCRP), which protect cells from bystander attack by autologous complement. These include CD59 (protectin), which prevents formation of the MAC complex in the terminal stages of complement activation. In the present study, we evaluated immunohistochemical expression of CD59 in a series of over 460 well-characterised colorectal cancers using tissue microarrays (TMA), and related this information to known tumour and patient variables and to survival. The CD59 expression was observed in 69 (15%) of cases overall, and was significantly associated with tumour grade. In contrast, no associations were noted with tumour site, stage or histological type. On survival analysis, a further correlation was observed between expression of CD59 by the colorectal tumours and a reduction in disease-specific patient survival. This observation was strongest for patients with early stage disease. However, a negative impact on survival was also seen in those patients with late stage disease. These results indicate that TMA linked to good clinicopathological databases with good long term follow up are useful tools for determining new prognostic indicators that can be used in future patient management. Immune surveillance may result in immune–editing that induces variable expression of a range of target antigens, and these may be useful prognostic markers. This study has identified CD59 expression as a marker of poor prognosis in colorectal cancer patients.This article is a symposium paper from the "Robert Baldwin Symposium: 50 years of Cancer Immunotherapy", held in Nottingham, Great Britain, on 30th June 2005.     

The retinoblastoma protein (Rb) as an anti-apoptotic factor: expression of Rb is required for the anti-apoptotic function of BAG-1 protein in colorectal tumour cells

Although the retinoblastoma-susceptibility gene RB1 is inactivated in a wide range of human tumours, in colorectal cancer, the retinoblastoma protein (Rb) function is often preserved and the RB locus even amplified. Importantly, we have previously shown that Rb interacts with the anti-apoptotic Bcl-2 associated athanogene 1 (BAG-1) protein, which is highly expressed in colorectal carcinogenesis. Here we show for the first time that Rb expression is critical for BAG-1 anti-apoptotic activity in colorectal tumour cells. We demonstrate that Rb expression not only increases the nuclear localisation of the anti-apoptotic BAG-1 protein, but that expression of Rb is required for inhibition of apoptosis by BAG-1 both in a γ-irradiated Saos-2 osteosarcoma cell line and colorectal adenoma and carcinoma cell lines. Further, consistent with the fact that nuclear BAG-1 has previously been shown to promote cell survival through increasing nuclear factor (NF)-κB activity, we demonstrate that the ability of BAG-1 to promote NF-κB activity is significantly inhibited by repression of Rb expression. Taken together, data presented suggest a novel function for Rb, promoting cell survival through regulating the function of BAG-1. As BAG-1 is highly expressed in the majority of colorectal tumours, targeting the Rb–BAG-1 complex to promote apoptosis has exciting potential for future therapeutic development.     

Array comparative genomic hybridization based identification of key genetic alterations at 2p21-p16.3 (MSH2, MSH6, EPCAM), 3p23-p14.2 (MLH1), 7p22.1 (PMS2) and 1p34.1-p33 (MUTYH) regions in hereditary non polyposis colorectal cancer (Lynch syndrome) in the Kingdom of Saudi Arabia

Lynch syndrome is inherited in an autosomal dominant mode. Lynch syndrome is caused by impairment of one or more of the various genes (most frequently MLH1 and MSH2) involved in mismatch repair. In this study, whole genome comparative genomic hybridization array (array CGH) based genomic analysis was performed on twelve Saudi Lynch syndrome patients. A total of 124 chromosomal alterations (structural loss) were identified at mean log2 ratio cut off value of ±0.25. We also found structural loss in 2p21-p16.3, 3p23-p14.2, 7p22.1 and 1p34.1-p33 regions. These findings were subsequently validated by real time quantitative PCR showing downregulation of MSH2, MSH6, EPCAM, MLH1, PMS2 and MUTYH genes. These findings shall help in establishing database for alterations in mismatch repair genes underlying Lynch syndrome in Saudi population as well as to determine the incidence ratio of these disorders. Guided counselling will subsequently lead to the prevention and eradication of Lynch Syndrome in the local population.