Analysis of p16 expression and allelic imbalance / loss of heterozygosity of 9p21 in cutaneous squamous cell carcinomas

Deletions of the short arm of chromosome 9 have been reported in different types of malignancies. This chromosomal region contains a number of known tumour suppressor genes, including the p16INK4A (CDKN2A), p15INK4B and MTAP tumour suppressor genes located at 9p21. In this study twenty-two paraffin embedded invasive cutaneous SCC were examined for allelic imbalance/ loss of heterozygosity (AI/LOH) of the 9p region (in particular 9p21), and for p16 protein expression. DNA was isolated from microdissected sections of normal and tumour cells and analysed for AI/LOH by using six fluorescently labelled microsatellite markers that map to the 9p region. P16 protein expression was examined by immunohistochemistry. At each of the six microsatellite markers the majority of SCC analysed showed AI/LOH. Overall both AI/LOH within the CDKN2A locus and absence of p16 protein expression were frequent among the cutaneous SCC analysed, suggesting that p16 inactivation may play a role in cutaneous SCC development. The majority of the SCC analysed also had AI/LOH of the marker within the MTAP gene, and at markers flanking the CDKN2A gene; thus further investigation as to a possible role for these genes in the development of cutaneous SCC is warranted.     

The significance of p16INK4a in cell defenses against transformation

Human cells, including fibroblast strains that have been immortalized by telomerase, are much more resistant to transformation than rodent cells. Most of the experimental evidence suggests that transformation of human fibroblasts requires inactivation of both the retinoblastoma (pRb) and p53 tumor suppressors as well as the addition of one or more dominant oncogenes. By starting with strains of primary fibroblast (Leiden and Q34 cells) that are genetically deficient for p16INK4a, we have been able to generate anchorage independent colonies simply by addition of telomerase (hTERT) and either Ras or Myc. Importantly, the transformed cells appear to retain pRb and p53 functions and are essentially diploid. Whereas Leiden cells expressing the individual oncogenes did not form tumors in mice, the combination of hTERT, Myc and Ras enabled them to become tumorigenic, albeit at a frequency suggestive of an additional genetic event. Significantly, we have obtained karyotypically stable tumors without the need to use DNA tumor virus oncoproteins and without deliberate ablation of p53.     

A novel p16INK4A mutation associated with esophageal squamous cell carcinoma in a high risk population

This study describes identification of p16^INK4A sequence variants and their potential association with esophageal squamous cell carcinoma (ESCC) in a high risk population from Kashmir, India. We report a novel 7 base pair exon 2 deletion in 22 out of 106 (~20%) surgically resected tumor samples. The deletion beginning at the second base of codon 103, results in a frame shift causing premature termination of the protein at codon 142, with structural and functional consequences predicted by insilico analysis. The described mutation is a previously unreported variant of p16^INK4A, perhaps representing a founder mutation unique to the population.     

A novel p16(INK4A) mutation associated with esophageal squamous cell carcinoma in a high risk population

This study describes identification of p16(INK4A) sequence variants and their potential association with esophageal squamous cell carcinoma (ESCC) in a high risk population from Kashmir, India. We report a novel 7 base pair exon 2 deletion in 22 out of 106 (~20%) surgically resected tumor samples. The deletion beginning at the second base of codon 103, results in a frame shift causing premature termination of the protein at codon 142, with structural and functional consequences predicted by insilico analysis. The described mutation is a previously unreported variant of p16(INK4A), perhaps representing a founder mutation unique to the population.     

Prognostic Value of Overexpressed p16INK4a in Vulvar Cancer: A Meta-Analysis

Objective

This study aimed to examine the prognostic value of overexpressed p16^INK4a in vulvar cancer. Although the tumor suppressor p16^INK4a has been shown to be of prognostic value in a wide variety of cancers and precancerous lesions, its role in the vulvar cancer is still unclear.

Methods

All publications in English language on the association between p16^INK4a and clinicopathological features of vulvar cancer were searched from Pubmed, Embase, and Web of Science, and those in Chinese language were identified manually and online from the China National Knowledge Infrastructure. Strict inclusion and exclusion criteria were followed. Odds ratios(ORs) or risk ratios(RRs) with 95% confidence intervals(CIs) were pooled to assess the strength of association. Publication bias was estimated using funnel plots and the Egger’s regression test.

Results

A total of 17 studies with 2309 patients were included. The p16^INK4a overexpression was found to correlate significantly with the lower International Federation of Gynecology and Obstetrics stage(I+II vs III+IV; OR = 0.60,95%CI:0.41–0.86,P = 0.006),negative lymph node metastasis(negative vs positive; OR = 0.61,95%CI:0.39–0.95,P = 0.029),patient’s age<55(OR = 0.54,95%CI:0.31–0.96,P = 0.034),human papillomavirus–positive status(OR = 0.01,95%CI:0.00–0.11,P<0.001),and higher overall survival(RR = 0.53,95%CI = 0.35–0.80,P = 0.003).

Conclusion

The p16^INK4a might be associated with a higher survival and indicates better prognosis of vulvar cancer.     

Requirements for cell cycle arrest by p16INK4a

Analysis of tumor-derived mutations has led to the suggestion that p16INK4a, cyclin D1, cdk4, and the retinoblastoma protein (pRB) are components of a regulatory pathway that is inactivated in most tumor cells. Cell cycle arrest induced by p16INK4a, an inhibitor of cyclin D-dependent kinases, requires pRB, and it has been proposed that this G1 arrest is mediated by pRB-E2F repressor complexes. By comparing the properties of primary mouse embryonic fibroblasts specifically lacking pRB-family members, we find that pRB is insufficient for a p16INK4a-induced arrest. In addition to pRB, a second function provided by either p107 or p130, two pRB-related proteins, is required for p16INK4a to block DNA synthesis. We infer that p16INK4a-induced arrest is not mediated exclusively by pRB, but depends on the nonredundant functions of at least two pRB-family members.     

Induction of apoptosis in p16INK4A mutant cell lines by adenovirus-mediated overexpression of p16INK4A protein

The tumor suppressor gene p16INK4A is a cyclin-dependent kinase inhibitor (CDKI) and an important cell cycle regulator. We have previously constructed a recombinant adenovirus which expresses p16 (Adp16) and shown that infection in a variety of human tumor cell lines with this recombinant virus results in high levels of p16INK4A protein expression resulting in cell cycle arrest and loss of cyclin-cdk activity. Furthermore, adenoviral-mediated overexpression of wild-type p16INK4A is more toxic in cancer cells which express mutant forms of p16INK4A compared to cancer cell lines containing endogenous wild-type p16. TUNEL assay and DAPI staining following infection of MDA-MB 231 breast cancer cells with Adp16 indicate that p16INK4A-mediated cytotoxicity was associated with apoptosis. This is supported by studies demonstrating a decrease in cpp32 and cyclinB1 protein levels and induction of poly (ADP-ribose) polymerase (PARP) cleavage following infection of MDA-MB-231 cells with Adp16. These results suggest that gene therapy using Adp16 may be a promising treatment option for human cancers containing alterations in p16 expression.     

p16INK4a基因的功能及其调控

p16INK4a蛋白能抑制CDK4和CDK6的活性,使pRb处于非磷酸化或低磷酸化状态而能与转录因子E2Fs结合,从而抑制DNA 的合成,阻止细胞由G1期进入S期.p16INK4a的表达受Ets1和Ets2的正调控,受Bmi-1的负调控.p16INK4a基因缺失、突变、甲基化、RNA剪接加工错误可导致细胞周期失控和癌变.应用p16INK4a对某些肿瘤进行基因治疗的研究正在进行中.     

Tumor suppressor INK4: determination of the solution structure of p18INK4C and demonstration of the functional significance of loops in p18INK4C and p16INK4A

Since the structures of several ankyrin-repeat proteins including the INK4 (inhibitor of cyclin-dependent kinase 4) family have been reported recently, the detailed structures and the functional roles of the loops have drawn considerable interest. This paper addresses the potential importance of the loops of ankyrin-repeat proteins in three aspects. First, the solution structure of p18INK4C was determined by NMR, and the loop structures were analyzed in detail. The loops adapt nascent antiparallel beta-sheet structures, but the positions are slightly different from those in the crystal structure. A detailed comparison between the solution structures of p16 and p18 has also been presented. The determination of the p18 solution structure made such detailed comparisons possible for the first time. Second, the [1H,15N]HSQC NMR experiment was used to probe the interactions between p18INK4C and other proteins. The results suggest that p18INK4C interacts very weakly with dna K and glutathione S-transferase via the loops. The third aspect employed site-specific mutagenesis and functional assays. Three mutants of p18 and 11 mutants of p16 were constructed to test functional importance of loops and helices. The results suggest that loop 2 is likely to be part of the recognition surface of p18INK4C or p16INK4A for CDK4, and they provide quantitative functional contributions of specific residues. Overall, our results enhance understanding of the structural and functional roles of the loops in INK4 tumor suppressors in particular and in ankyrin-repeat proteins in general.     

Matrix proteoglycans are markedly affected in advanced laryngeal squamous cell carcinoma

Proteoglycans (PGs) are implicated in the growth and progression of malignant tumors. In this study, we examined the concentration and localization of PGs in advanced (stage IV) laryngeal squamous cell carcinoma (LSCC) and compared with human normal larynx (HNL). LSCC and HNL sections were examined immunohistochemically with a panel of antibodies, and tissues extracts were analyzed by biochemical methods including immunoblotting and high performance liquid chromatography (HPLC). The results demonstrated significant destruction of cartilage in LSCC, which was followed by marked decrease of aggrecan and link protein. In contrast to the loss of aggrecan in LSCC, accumulation of versican and decorin was observed in the tumor-associated stroma. Biochemical analyses indicated that aggrecan, versican, decorin and biglycan comprise the vast majority of total PGs in both healthy and cancerous tissue. In LSCC the absolute amounts of KS/CS/DS-containing PGs were dramatically decreased about 18-fold in comparison to HNL. This decrease is due to the loss of aggrecan. Disaccharide analysis of CS/DSPGs from LSCC showed a significant reduction of 6-sulfated Delta-disaccharides (Deltadi-6S) with a parallel increase of 4-sulfated Delta-disaccharides (Deltadi-4S) as compared to HNL. The obtained data clearly demonstrate that tumor progression is closely related to specific alteration of matrix PGs in LSCC. The altered composition of PGs in cartilage, as well as in tumor-associated stroma, is crucial for the biological behaviour of cancer cells in the diseased tissue.     

Differential expression levels of urokinase-type plasminogen activator and cathepsin D in locally advanced laryngeal squamous cell carcinoma: clinical implications

The expression levels and the prognostic impact of urokinase-type plasminogen activator (uPA) and cathepsin D (CD) were evaluated in patients with locally advanced laryngeal squamous cell carcinoma (LSCC). uPA and CD protein levels were determined by immunoluminometric or immunoenzymatic assays in the cytosol of paired sets of tumor tissues and corresponding adjacent normal mucosa (NLM) from 57 patients with stage III/IV LSCC and were correlated with a number of clinicobiological parameters of this tumor including anatomical site, tumor grade, nodal status, clinical stage, DNA ploidy, proliferation rate, and patient outcome. Median uPA levels were significantly higher in LSCC than in NLM (1.8 ng/mg of protein vs 0.3 ng/mg; p<0.001) whereas median CD levels were not significantly increased in tumor tissue compared to NLM (24 pmol/mg vs 19 pmol/mg, p=0.063). No significant correlation was observed between uPA and CD concentrations in tumor tissues (r=-0.1; p=0.4). Furthermore, the distribution analysis of uPA and CD in tumors showed no correlation between expression levels of these proteinases and the parameters mentioned above including patient outcome. However, when data were matched according to each parameter examined it was observed that the differences in uPA content between LSCC and NLM, expressed as uPA tumor/normal tissue ratio (T/M), were more marked in clinically advanced and/or aggressive forms of LSCC (i.e., node positive, stage IV, poorly and moderately differentated, aneuploid multiclonal, low S-phase, subglottis tumors). These data suggest that in such tumors altered regulation of uPA may occur to a greater extent than in less aggressive and less advanced forms of LSCC. This phenomenon was not observed for CD. However, in tumors with a high proliferation rate, in stage IV tumors as well as in those located in the supraglottis, CD levels were significantly higher than those found in the corresponding NLM (p=0.008, p=0.02 and p=0.03, respectively). In conclusion, uPA is highly expressed in locally advanced LSCC and appears to be implicated in some key events of progression of this tumor such as local invasion and/or nodal involvement, whereas CD does not seem to have a role in promoting these processes. Nevetheless, neither of these proteinases seem to be prognostically useful in patients with stage III/IV tumors.     

Prognostic Significance of Overexpressed p16INK4a in Patients with Cervical Cancer: A Meta-Analysis

Background

p16^INK4a is a tumor suppressor protein which is induced in cells upon the interaction of high-risk HPV E7 with the retinoblastoma protein by a positive feedback loop, but cannot exert its suppressing effect. Previous reports suggested that p16^INK4a immunostaining allows precise identification of even small CIN or cervical cancer lesions in biopsies. The prognostic value of overexpressed p16^INK4a in cervical cancer has been evaluated for several years while the results remain controversial. We performed a systematic review and meta-analysis of studies assessing the clinical and prognostic significance of overexpression of p16^INK4a in cervical cancer.

Methods

Identification and review of publications assessing clinical or prognostic significance of p16^INK4a overexpression in cervical cancer until March 1, 2014. A meta-analysis was performed to clarify the association between p16^INK4a overexpression and clinical outcomes.

Results

A total of 15 publications met the criteria and comprised 1633 cases. Analysis of these data showed that p16^INK4a overexpression was not significantly associated with tumor TNM staging (I+II vs. III+IV) (OR = 0.75, 95% confidence interval [CI]: 0.35–1.63, P = 0.47), the tumor grade (G1+ G2 vs. G3) (OR = 0.78, 95% CI: 0.39–1.57, P = 0.49), the tumor size (<4 vs. ≥4 cm) (OR = 1.10, 95% CI: 0.45–2.69, P = 0.83), or vascular invasion (OR = 1.20, 95% CI: 0.69–2.08, P = 0.52). However, in the identified studies, overexpression of p16^INK4a was highly correlated with no lymph node metastasis (OR = 0.51, 95% CI: 0.28–0.95, P = 0.04), increased overall survival (relative risk [RR]: 0.42, 95% CI: 0.24–0.72, P = 0.002) and increased disease free survival (RR: 0.60, 95% CI: 0.44–0.82, P = 0.001).

Conclusions

This meta-analysis shows overexpression of p16^INK4a in cervical cancer is connected with increased overall and disease free survival and thus marks a better prognosis.     

The p16INK4a tumor suppressor controls p21WAF1 induction in response to ultraviolet light

p16^INK4a and p21^WAF1, two major cyclin-dependent kinase inhibitors, are the products of two tumor suppressor genes that play important roles in various cellular metabolic pathways. p21^WAF1 is up-regulated in response to different DNA damaging agents. While the activation of p21^WAF1 is p53-dependent following γ-rays, the effect of ultraviolet (UV) light on p21^WAF1 protein level is still unclear. In the present report, we show that the level of the p21^WAF1 protein augments in response to low UVC fluences in different mammalian cells. This up-regulation is mediated through the stabilization of p21^WAF1 mRNA in a p16^INK4a-dependent manner in both human and mouse cells. Furthermore, using p16-siRNA treated human skin fibroblast; we have shown that p16 controls the UV-dependent cytoplasmic accumulation of the mRNA binding HuR protein. In addition, HuR immunoprecipitations showed that UV-dependent binding of HuR to p21 mRNA is p16-related. This suggests that p16 induces p21 by enabling the relocalization of HuR from the nucleus to the cytoplasm. Accordingly, we have also shown that p16 is necessary for efficient UV-dependent p53 up-regulation, which also requires HuR. These results indicate that, in addition to its role in cell proliferation, p16^INK4a is also an important regulator of the cellular response to UV damage.     

Prognostic significance of CD34 expression in early cervical squamous cell carcinoma

The aim of the study was to evaluate angiogenesis as an independent prognostic factor and to determine the correlation of the microvessel density (MD) with lymph node metastases and survival rate in 73 women operated because of invasive squamous cell carcinoma (SCC) of the uterine cervix at clinical stages lb and IIa (FIGO). The patients were divided into two groups: I--25 (34.4%) with survival rate <5 years and II--48 (65.6%) with survival rate >5 years. Angiogenesis was quantified in light microscope using an assay for CD34. The CD34 antibody intensely immunostained single endothelial cells as well as larger microvessels. In the study. differences were revealed by comparing the MD between both groups. The 5-year overall survival rate for patients with high MD was significantly worse than for those with low MD (p<0.003). A correlation was found between angiogenesis intensity and vascular involvement as well as the incidence of lymph node metastases. Thus, tissue expression of CD34 in SCC appears to be a significant prognostic indicator.     

The OGF-OGFr axis utilizes the p16INK4a and p21WAF1/CIP1 pathways to restrict normal cell proliferation

Opioid growth factor (OGF) is an endogenous opioid peptide ([Met⁵]enkephalin) that interacts with the OGF receptor (OGFr) and serves as a tonically active negative growth factor in cell proliferation of normal cells. To clarify the mechanism by which OGF inhibits cell replication in normal cells, we investigated the effect of the OGF–OGFr axis on cell cycle activity in human umbilical vein endothelial cells (HUVECs) and human epidermal keratinocytes (NHEKs). OGF markedly depressed cell proliferation of both cell lines by up to 40% of sterile water controls. Peptide treatment induced cyclin-dependent kinase inhibitor (CKI) p16^INK4a protein expression and p21^WAF1/CIP1 protein expression in HUVECs and NHEKs, but had no effect on p15, p18, p19, or p27 protein expression in either cell type. Inhibition of either p16^INK4a or p21^WAF1/CIP1 activation by specific siRNAs blocked OGF inhibitory action. Human dermal fibroblasts and mesenchymal stem cells also showed a similar dependence of OGF action on p16^INK4a and p21^WAF1/CIP1. Collectively, these results indicate that both p16^INK4a and p21^WAF1/CIP1 are required for the OGF–OGFr axis to inhibit cell proliferation in normal cells.     

Prognostic significance of NDRG1 expression in oral and oropharyngeal squamous cell carcinoma

Human N-myc downstream-regulated gene 1 (NDRG1) is a metastasis suppressor gene with several potential functions, including cell differentiation, cell cycle regulation and response to hormones, nickel and stress. The purpose of this study was to investigate the immunoexpression of NDRG1 in oral and oropharyngeal squamous cell carcinomas searching for its role in the clinical course of these tumors. We investigated immunohistochemical expression of NDRG1 protein in 412 tissue microarray cores of tumor samples from 103 patients with oral and oropharyngeal squamous cell carcinomas and in 110 paraffin-embedded surgical margin sections. The results showed NDRG1 up-regulation in 101/103 (98.1?%) tumor samples, but no expression in any normal tissue sample. Western blot assays confirmed the immunohistochemical findings, suggesting that lower levels of NDRG1 are associated with a high mortality rate. NDRG1 overexpression was related to long-term specific survival (HR?=?0.38; p?=?0.009), whereas the presence of lymph-node metastasis showed the opposite association with survival (HR?=?2.45; p?=?0.013). Our findings reinforce the idea that NDRG1 plays a metastasis suppressor role in oral and oropharyngeal squamous cell carcinomas and may be a useful marker for these tumors.     

E-cad和Gal-3在喉鳞状细胞癌中的表达及其临床意义

目的 探讨E钙粘蛋白(E-cadherin E-cad)与β-半乳糖凝集素3(galectin-3 Gal-3)蛋白在喉鳞状细胞癌(laryngeal squamous cell carcinoma LSCC)中的表达及与临床病理因素的关系.方法 采用免疫组织化学ElivisionTM plus法检测83例LSCC和20例正常喉组织中E-cad和Gal-3的表达情况.结果 在正常喉组织中E cad和Gal 3的表达率分别为100％和20.0％,在LSCC组织中分别为39.8％和79.5％,两组相比,差异有显著性(P＜0.01).E-cad和Gal的表达水平与LSCC肿瘤细胞分化程度、淋巴结转移与否和临床分期高低有关(全部P＜0.05),与患者的年龄、性别、肿瘤大小及临床分型无关(P＞0.05);且E-cad的表达水平与Gal-3的表达水平呈负相关.结论 E-cad和Gal-3蛋白可能参与了LSCC的发生,并且与LSCC的侵袭及转移密切相关,联合检测E-cad和Gal-3的表达可作为临床早期判断LSCC侵袭、转移的指标之一.