Ovarian cancer cells that coexpress endogenous Rb and p16 are insensitive to overexpression of functional p16 protein

CDKN2A was a cuproptosis-related gene in regulating chemotherapy resistance by the MAGE-A family in breast cancer: based on artificial intelligence (AI)-constructed pan-cancer risk model

BACKGROUND

Before the discovery of cuproptosis, copper-loaded nanoparticle is a wildly applied strategy for enhancing the tumor-cell-killing effect of chemotherapy. Although copper(ii)-related researches are wide, details of cuproptosis-related bioprocess in pan-cancer are not clear yet now, especially for prognosis and drug sensitivity prediction yet now.

METHODS

In this study, VOSviewer is used for the literature review, and R4.2.0 is used for data analysis. Public data are collected from TCGA and GEO, local breast cancer cohort is collected to verify the expression level of CDKN2A.

RESULTS

7036 published articles exhibited a time-dependent linear relationship (R=0.9781, p<0.0001), and breast cancer (33.4%) is the most researched topic. Cuproptosis-related-genes (CRGs)-based unsupervised clustering divides pan-cancer subgroups into four groups (CRG subgroup) with differences in prognosis and tumor immunity. 44 tumor-driver-genes (TDGs)-based prediction model of drug sensitivity and prognosis is constructed by artificial intelligence (AI). Based on TDGs and clinical features, a nomogram is (C- index: 0.7, p= 6.958e- 12) constructed to predict the prognosis of breast cancer. Importance analysis identifies CDKN2A has a pivotal role in AI modeling, whose higher expression indicates worse prognosis in breast cancer. Furthermore, inhibition of CDKN2A down-regulates decreases Snail1, Twist1, Zeb1, vimentin and MMP9, while E-cadherin is increased. Besides, inhibition of CDKN2A also decreases the expression of MEGEA4, phosphorylated STAT3, PD-L1, and caspase3, while cleaved-caspase3 is increased. Finally, we find down-regulation of CDKN2A or MAGEA inhibits cell migration and wound healing, respectively.

CONCLUSIONS

AI identified CRG subgroups in pan-cancer based on CRGs-related TDGs, and 44-gene-based AI modeling is a novel tool to identify chemotherapy sensitivity in breast cancer, in which CDKN2A/MAGEA4 pathway played the most important role.

Comprehensive Analysis Revealed that CDKN2A is a Biomarker for Immune Infiltrates in Multiple Cancers

The CDKN2A (cyclin dependent kinase inhibitor 2A/multiple tumor suppressor 1) gene, also known as the P16 gene, encodes multiple tumor suppressor 1 (MTS1), which belongs to the INK4 family. In tumor tissue, CDKN2A has a high expression level compared with normal tissue and reflects prognosis in tumor patients. Our research targeted the analysis of CDKN2A expression in 33 tumors and clinical parameters, patient prognosis and tumor immunity roles. The CDKN2A expression level was significantly correlated with the tumor mutation burden (TMB) in 10 tumors, and the expression of CDKN2A was also correlated with MSI (microsatellite instability) in 10 tumors. CDKN2A expression was associated with infiltrating lymphocyte (TIL) levels in 22 pancancers, thus suggesting that CDKN2A expression is associated with tumor immunity. Enrichment analysis indicated that CDKN2A expression was involved in natural killer cell-mediated cytotoxicity pathways, antigen processing and presentation, olfactory transduction pathways, and regulation of the autophagy pathway in multiple cancers. CDKN2A was significantly associated with several immune cell infiltrates in pantumors. CDKN2A may serve as a promising prognostic biomarker and is associated with immune infiltrates across cancers.

Oncolytic adenovirus shapes the ovarian tumor microenvironment for potent tumor-infiltrating lymphocyte tumor reactivity

Background

Ovarian cancers often contain significant numbers of tumor-infiltrating lymphocytes (TILs) that can be readily harnessed for adoptive T-cell therapy (ACT). However, the immunosuppressive ovarian tumor microenvironment and lack of tumor reactivity in TILs can limit the effectiveness of the therapy. We hypothesized that by using an oncolytic adenovirus (Ad5/3-E2F-D24-hTNFa-IRES-hIL2; TILT-123) to deliver tumor necrosis factor alpha (TNFa) and interleukin-2 (IL-2), we could counteract immunosuppression, and enhance antitumor TIL responses in ovarian cancer (OVCA).

Methods

We established ex vivo tumor cultures freshly derived from patients with advanced OVCA and evaluated the effects of Ad5/3-E2F-D24-hTNFa-IRES-hIL2 or Ad5/3-E2F-D24 (the control virus without TNFa and IL-2) on TILs, cytokine response and tumor viability. Tumor reactivity was assessed by determining interferon gamma (IFNg) response of clinically relevant TILs towards autologous T-cell-depleted ex vivo tumor cultures pretreated with or without the aforementioned oncolytic adenoviruses.

Results

Treatment of ex vivo tumor cultures with Ad5/3-E2F-D24-hTNFa-IRES-hIL2 caused a substantial rise in proinflammatory signals: increased secretion of IFNg, CXCL10, TNFa and IL-2, and concomitant activation of CD4+ and CD8+ TILs. Potent tumor reactivity was seen, as clinically relevant TIL secreted high levels of IFNg in response to autologous T-cell-depleted ovarian ex vivo tumor cultures treated with Ad5/3-E2F-D24-hTNFa-IRES-hIL2. This phenomenon was independent of PD-L1 expression in tumor cells, a factor that determined the variability of IFNg responses seen in different patient samples.

Conclusions

Overall, oncolytic adenovirus Ad5/3-E2F-D24-hTNFa-IRES-hIL2 was able to rewire the ovarian tumor microenvironment to accommodate heightened antitumor TIL reactivity. Such effects may improve the clinical effectiveness of ACT with TILs in patients with advanced OVCA.

On-chip immunofluorescence analysis of single cervical cells using an electroactive microwell array with barrier for cervical screening

Several specific tests for cervical screening have been developed recently, including p16/Ki67 dual immunostaining for diagnosing high-risk human papillomavirus positive squamous intraepithelial lesion in the cervix. However, manual screening of cells in an entire glass slide is currently a standard clinical procedure for quantification and interpretation of immunocytochemical features of the cells. Here, we developed a microfluidic device containing an electroactive microwell array with barriers (EMAB) for highly efficient single-cell trapping followed by on-chip immunofluorescence analysis with minimum loss of the sample. EMAB utilizes patterned electrodes at the bottom of cell-sized microwells to trap single cells using dielectrophoresis (DEP) and cell-holding structures behind the microwells to stabilize the position of trapped cells even without DEP. Using the device, we evaluated the performance of p16/Ki67 dual immunostaining of HeLa cells on the chip. The device shows 98% cell-trapping efficiency as well as 92% cell-holding efficiency against the fixed HeLa cells, and we successfully demonstrated high-efficiency on-chip immunofluorescence analysis with minimal loss of sample. p16/Ki67 dual immunostaining using EMAB may be useful for complementary tests for cervical screening in confirming the histopathological diagnosis.

Doxycycline-Regulated p16MTS1 Expression Suppresses the Anchorage-Independence and Tumorigenicity of Breast Cancer Cell Lines that Lack Endogenous p16

The RB pathway controls the critical transition from G1 into S phase of the mammalian cell cycle. Deregulation of the RB pathway by means of RB or p16 inactivation has been implicated in the development of virtually all human cancers. Such findings have led to the view that the loss of RB-mediated regulation at the G1/S checkpoint is a precondition for human malignancy. Our analysis of the RB-positive MCF-7 and ZR75.1 breast cancer cell lines revealed a lack of endogenous p16 protein expression as a result of the homozygous deletion and methylation of the p16 gene at the CDKN2A locus, respectively. We employed the TET-OFF inducible expression system to investigate the effects of non-growth inhibitory levels of functional p16 protein upon the in vitro and in vivo transformed properties of the MCF-7 and ZR75.1 cell lines. Stable transfectants of MCF-7 and ZR75.1 cells were isolated that expressed different levels of p16 protein in the absence of doxycycline (DOX) but continued to proliferate in culture. Transfectants that expressed modest levels of p16 (relative to SV40 T antigen-transformed HBL-100 breast epithelial cells) demonstrated a marked suppression of anchorage-independent growth in soft agar. Further, the induction of moderate and high levels of p16 (relative to HBL-100) resulted in the suppression of tumorigenicity of both MCF-7 and ZR75.1 cells as assayed by injection into nude mice. From these data, we concluded that RB pathway restoration by non-growth inhibitory levels of p16 protein was sufficient to revert breast cancer cells to a non-transformed and non-tumorigenic state.

Comparative analysis of Rb1, P16 and ER as diagnostic, prognostic and potential targets for therapeutic agents in ovarian epithelial tumors: an immunohistochemical study of 130 ovarian carcinomas

BACKGROUND

Deregulation of CDK4/6, cyclin D/P16 and retinoblastoma (Rb) are known aberrations in certain malignancies. There has been a recent interest in exploring the combination of letrozole and CDK4/6 inhibitors in recurrent ER+ ovarian cancers.

METHODS

This study aimed to determine the frequency of expression of Rb1, P16 and ER in ovarian epithelial tumors by immunohistochemistry.

RESULTS

Co-expression of all 3 markers studied was seen in 10% of high grade serous carcinoma (HGSC) and low grade serous carcinoma (LGSC). Coordinate expression of Rb1+ and ER+ in HGSC and LGSC was seen in 67% of grade 1/2 vs. 44 % of grade three tumors (p < 0.05). The reverse was true with positive P16 staining in 73% of grade three vs. 32% of grade 1/2 tumors (p < 0.001).

CONCLUSIONS

Coordinate pattern of Rb1+ and ER+ in HGSC and LGSC is 19 and 50%, respectively. Rb1 and P16 show inverse expression pattern according to tumor grade with more frequent Rb1 in low grade vs. more frequent P16 in grade 3 tumors. These data provide a rational basis for clinical trials that aim to target these proteins.

Pathway modulations and epigenetic alterations in ovarian tumorbiogenesis

Cellular pathways are numerous and are highly integrated in function in the control of cellular systems. They collectively regulate cell division, proliferation, survival and apoptosis of cells and mutagenesis of key genes that control these pathways can initiate neoplastic transformations. Understanding these pathways is crucial to future therapeutic and preventive strategies of the disease. Ovarian cancers are of three major types; epithelial, germ-cell, and stromal. However, ovarian cancers of epithelial origin, arising from the mesothelium, are the predominant form. Of the subtypes of ovarian cancer, the high-grade serous tumors are fatal, with low survival rate due to late detection and poor response to treatments. Close examination of preserved ovarian tissues and in vitro studies have provided insights into the mechanistic changes occurring in cells mediated by a few key genes. This review will focus on pathways and key genes of the pathways that are mutated or have aberrant functions in the pathology of ovarian cancer. Non-genetic mechanisms that are gaining prominence in the pathology of ovarian cancer, miRNAs and epigenetics, will also be discussed in the review.

Altered p16(INK4) and RB1 Expressions Are Associated with Poor Prognosis in Patients with Nonsmall Cell Lung Cancer

p16(INK4) and RB1 are two potent cell cycle regulators to control the G1/S transition by interacting with CDK4/6, E2F, and D-type cyclins, respectively. Depending on the tumour type, genetic alterations resulting in the functional inactivation have frequently been reported in both genes. By contrast, much less is known regarding the overexpression of these proteins in the tumor cells. In this study, expressions of p16(INK4) RB1, and CDKN2A copy number variances (CNV) in the tumor cells were assessed by immunohistochemistry and fluorescence in situ hybridization (FISH), respectively, in 73 nonsmall cell lung cancer (NSCLC) with known 5-year survivals. The histologic type (P = 0.01), p16(INK4) (P = 0.004), and RB1 (P < 0.001) were predictive of survivals. The CDKN2A CNV (P < 0.05) was also significant when compared to those cases without CNV. Therefore, among the molecular genetic prognostic factors, expressions of RB1 and p16(INK4) in the tumor cells were the most strongly predictive of adverse outcomes in stage I and II nonsquamous NSCLC.

Identifying microRNA/mRNA dysregulations in ovarian cancer

BACKGROUND

MicroRNAs are a class of noncoding RNA molecules that co-regulate the expression of multiple genes via mRNA transcript degradation or translation inhibition. Since they often target entire pathways, they may be better drug targets than genes or proteins. MicroRNAs are known to be dysregulated in many tumours and associated with aggressive or poor prognosis phenotypes. Since they regulate mRNA in a tissue specific manner, their functional mRNA targets are poorly understood. In previous work, we developed a method to identify direct mRNA targets of microRNA using patient matched microRNA/mRNA expression data using an anti-correlation signature. This method, applied to clear cell Renal Cell Carcinoma (ccRCC), revealed many new regulatory pathways compromised in ccRCC. In the present paper, we apply this method to identify dysregulated microRNA/mRNA mechanisms in ovarian cancer using data from The Cancer Genome Atlas (TCGA).

METHODS

TCGA Microarray data was normalized and samples whose class labels (tumour or normal) were ambiguous with respect to consensus ensemble K-Means clustering were removed. Significantly anti-correlated and correlated genes/microRNA differentially expressed between tumour and normal samples were identified. TargetScan was used to identify gene targets of microRNA.

RESULTS

We identified novel microRNA/mRNA mechanisms in ovarian cancer. For example, the expression level of RAD51AP1 was found to be strongly anti-correlated with the expression of hsa-miR-140-3p, which was significantly down-regulated in the tumour samples. The anti-correlation signature was present separately in the tumour and normal samples, suggesting a direct causal dysregulation of RAD51AP1 by hsa-miR-140-3p in the ovary. Other pairs of potentially biological relevance include: hsa-miR-145/E2F3, hsa-miR-139-5p/TOP2A, and hsa-miR-133a/GCLC. We also identified sets of positively correlated microRNA/mRNA pairs that are most likely result from indirect regulatory mechanisms.

CONCLUSIONS

Our findings identify novel microRNA/mRNA relationships that can be verified experimentally. We identify both generic microRNA/mRNA regulation mechanisms in the ovary as well as specific microRNA/mRNA controls which are turned on or off in ovarian tumours. Our results suggest that the disease process uses specific mechanisms which may be significant for their utility as early detection biomarkers or in the development of microRNA therapies in treating ovarian cancers. The positively correlated microRNA/mRNA pairs suggest the existence of novel regulatory mechanisms that proceed via intermediate states (indirect regulation) in ovarian tumorigenesis.

Alteration of cell-cycle regulation in epithelial ovarian cancer

In spite of the clinical importance of epithelial ovarian cancer (EOC), little is known about the pathobiology of its precursor lesions and progression. Regulatory mechanisms of the cell cycle are mainly composed of cyclins, cyclin-dependent kinases (CDK), and CDK inhibitors. Alteration of these mechanisms results in uncontrolled cell proliferation, which is a distinctive feature of human cancers. This review describes the current state of knowledge about the alterations of cell-cycle regulations in the context of p16-cyclin D1-CDK4/6-pRb pathway, p21-p27-cyclin E-CDK2 pathway, p14-MDM2-p53 pathway, and ATM-Chk2-CDC25 pathway, respectively. Recent evidence suggests that ovarian cancer is a heterogenous group of neoplasms with several different histologic types, each with its own underlying molecular genetic mechanism. Therefore, expression of cell cycle regulatory proteins should be tested separately according to each histologic type. In serous ovarian carcinoma, high expression of p16, p53, and p27 and low expression of p21 and cyclin E were shown. In addition, this review focuses on the prognostic significance of cell cycle-regulating proteins in EOC. However, it is difficult to compare the results from different groups due to diverse methodologies and interpretations. Accordingly, researchers should establish standardized criteria for the interpretation of immunohistochemical results.

Regulation of CDKN2A/B and Retinoblastoma genes in Xiphophorus melanoma

Xiphophorus interspecies hybrids provide several well-characterized genetic models of melanoma susceptibility. The Xiphophorus CDKN2A/B gene, homologous to mammalian CDKN2A/B cyclin-dependent kinase inhibitors (p16 and p15), is a candidate tumor susceptibility gene in these models. Using real-time PCR and Western blot analysis, we analyzed expression of CDKN2A/B in spontaneous and UV-induced primary melanomas from individual backcross hybrid fish. We found that CDKN2A/B mRNA is highly expressed in melanomas (18-fold), relative to other fish tissues. Expression is also elevated, to a lesser extent (9.5-fold), in melanized skin from tumor-bearing fish. However, quantitative levels of CDKN2A/B mRNA in tumors varied considerably and positively correlated with expression of the Xmrk oncogene, suggesting possible functional interaction between Xmrk and CDKN2A/B expression. As a homolog corresponding to members of the mammalian CDKN2 family which regulate cell cycle progression at the G1 checkpoint, the CDKN2A/B p13 protein is a putative regulator of the G1 checkpoint apparatus in Xiphophorus. Since CDKN2A is often observed to be inversely regulated compared to RB in some human tumors, and is capable of transcriptionally regulating RB in human ovarian tumors, we cloned the Xiphophorus maculatus RB cDNA and analyzed RB expression by real-time PCR and Western blot analysis in the fish melanomas. These experiments were designed to ascertain whether CDKN2A/B and RB expression were inversely correlated. Our results indicate that RB mRNA was consistently expressed at only a 2-fold higher level in both tumors and melanized skin than in muscle. Qualitatively similar results were obtained for protein expression. These results collectively suggest that (i) Xmrk and CDKN2A/B may be co-regulated at the transcriptional level, and (ii) there is little, if any, alteration of RB expression in Xiphophorus melanomas.

Abnormalities of the RB1 pathway in ovarian serous papillary carcinoma as determined by overexpression of the p16(INK4A) protein

Dysfunction of proteins involved in the G1 to S transition of the cell cycle, such as p16(INK4A) and RB1, is common in many cancer types. A screen of p16 protein expression was performed in benign, borderline, and invasive ovarian tumors, together with endometrial cancers, aligned on a tissue microarray. We observed frequent p16 overexpression in serous papillary carcinomas of ovarian and endometrial origin. An extended cohort of ovarian serous papillary carcinomas was examined to further evaluate the frequency of p16 overexpression. Strong, uniform staining in the majority of cancer cells occurred commonly in invasive serous papillary ovarian cancers, particularly in grade 3 carcinomas. RB1 protein expression abnormalities were rare. Our data indicate that abnormalities in the retinoblastoma pathway, as determined by p16 overexpression, are common in serous papillary carcinomas and are probably an early event.

Cell cycle genes in ovarian cancer: steps toward earlier diagnosis and novel therapies

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell cycle-regulatory mechanisms. The regulatory pathways controlling cell cycle phases include several oncogenes and tumor suppressor genes that display a range of abnormalities with potential usefulness as markers of evolution or treatment response in ovarian cancer. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary. We sought to divide cell cycle-regulatory genes into four subgroups on the basis of their predominant role in a specific phase or during the transition between two phases of the cell cycle.

Resveratrol causes Cdc2-tyr15 phosphorylation via ATM/ATR-Chk1/2-Cdc25C pathway as a central mechanism for S phase arrest in human ovarian carcinoma Ovcar-3 cells

Resveratrol is one of the most extensively studied cancer chemopreventive agents; however, its mechanisms of action are not completely understood. Here, we observed that resveratrol induces S phase arrest via Tyr15 phosphorylation of Cdc2 in human ovarian carcinoma Ovcar-3 cells. Overexpression of Cdc2AF, a mutant resistant to Thr14 and Tyr15 phosphorylation, ablated resveratrol-induced S phase arrest. Further upstream, we observed that resveratrol causes phosphorylation of cell division cycle 25C (Cdc25C) tyrosine phosphatase via the activation of checkpoint kinases Chk1 and Chk2, which in turn were activated via ATM (ataxia telangiectasia mutated)/ATR (ataxia telangiectasia-Rad3-related) kinase in response to DNA damage, as resveratrol also increased phospho-H2A.X (Ser139), which is known to be phosphorylated by ATM/ATR in response to DNA damage. The involvement of these molecules in resveratrol-induced S phase was also supported by the studies showing that addition of ATM/ATR inhibitor caffeine reverses resveratrol-caused activation of ATM/ATR-Chk1/2 as well as phosphorylation of Cdc25C, Cdc2 and H2A.X, and S phase arrest. In additional studies assessing whether observed effects of resveratrol are specific to Ovcar-3 cells, we observed that it also induces S phase arrest and H2A.X (Ser139) phosphorylation in other ovarian cancer cell lines PA-1 and SKOV-3, albeit at different levels; whereas, resveratrol showed only marginal S phase arrest in normal human foreskin fibroblasts with undetectable level of phospho-H2A.X (Ser139). These findings for the first time identify that resveratrol causes Cdc2-tyr15 phosphorylation via ATM/ATR-Chk1/2-Cdc25C pathway as a central mechanism for DNA damage and S phase arrest selectively in ovarian cancer cells, and provide a rationale for the potential efficacy of ATM/ATR agonists in the prevention and intervention of cancer.

Role of cell-cycle regulatory proteins in gynecological cancer

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell-cycle regulatory mechanisms. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary, endometrium, cervix uteri, and vulva. The data indicate that analysis of single cell cycle stimulating or inhibiting proteins partly produces unexpected, apparently paradoxical results, and cell-cycle regulatory pathways should be regarded as a whole in order to identify the molecular mechanisms leading to abnormal tumor cell proliferation. For the papillomavirus (HPV)- associated cervical and vulvar carcinomas, the manifold effects of the viral oncogenes E6 and E7 on cell-cycle control are described.

Telomere maintenance and cell cycle regulation in spontaneously immortalized T-cell lines from Nijmegen breakage syndrome patients

Nijmegen breakage syndrome (NBS) is a rare genetic instability syndrome associated with a high incidence of lymphoid malignancies. The NBS1 protein has been implicated in telomere biology suggesting that cells from NBS patients might have deficient telomere maintenance capacity. In this study we characterized spontaneously immortalized T-cell lines derived from three NBS patients regarding growth characteristics, telomere biology, expression of cell-cycle regulators, and response to DNA damage to understand the role of NBS1 in the immortalization process. In all the NBS T-cell lines the acquisition of an immortal phenotype was associated with telomere length stabilization, high telomerase activity, and increased mRNA expression of the catalytic subunit of telomerase (hTERT), together with c-myc up-regulation. Our findings provide evidence that telomere length maintenance was intact in the T lymphocytes in the absence of a full-length NBS protein, presumably due to the presence of an alternatively transcribed NBS protein of 70 kDa. Normal protein expression patterns for pRb and p53 in all the immortal lines coincided with altered expression of some cell-cycle proteins as well as with an impaired G1/S arrest after gamma irradiation, despite a seemingly normal p53/p21 pathway. The here described, spontaneously immortalized NBS derived T-cell lines can be useful in future analysis of the biologic effects in the NBS.

Dual mechanisms for lysophosphatidic acid stimulation of human ovarian carcinoma cells

BACKGROUND

Lysophosphatidic acid (LPA), at concentrations present in ascitic fluid, indirectly stimulates the growth of malignant ovarian tumors by increasing the expression of vascular endothelial growth factor (VEGF) in ovarian cancer cells. We investigated whether LPA could also directly promote ovarian tumor growth by increasing the level of cyclin D1, a key G1-phase checkpoint regulator, which thereby increases cell proliferation.

METHODS

Expression of cyclin D1 and LPA receptors (EDG4 and EDG7) was determined in six ovarian cancer cell lines (including OVCAR-3 cells) and immortalized ovarian surface epithelial cells (IOSE-29). Cyclin D1 promoter activity was measured in LPA-treated OVCAR-3 cells cotransfected with cyclin D1 promoter-driven luciferase constructs and cDNA expression plasmids for IkappaBalphaM (a nuclear factor kappaB [NFkappaB] super-repressor).

RESULTS

Four of six cancer cell lines, including OVCAR-3, overexpressed cyclin D1 protein relative to levels in IOSE-29 cells. LPA treatment increased cyclin D1 protein in a dose- and time-dependent manner in OVCAR-3 cells but not in IOSE-29 cells. LPA stimulated cyclin D1 promoter activity (3.0-fold, 95% confidence interval [CI] = 2.7-fold to 3.3-fold). Mutation of the NFkappaB-binding site in the cyclin D1 promoter to block NFkappaB binding and expression of IkappaBalphaM, which binds NFkappaB and inhibits its binding to the promoter, markedly diminished LPA stimulation of cyclin D1 promoter activity (activity stimulated only 1.4-fold, 95% CI = 1.1-fold to 1.7-fold, and 0.7-fold, 95% CI = 0.6-fold to 0.8-fold, respectively). EDG4 was overexpressed in all cancer cell lines studied relative to that in IOSE-29 cells, but EDG7 was overexpressed in only two lines.

CONCLUSIONS

Dual mechanisms are probably involved in LPA stimulation of ovarian tumor growth in vivo. In addition to the previously characterized indirect mechanism that increases angiogenesis via VEGF, LPA may directly increase the level of cyclin D1 in ovarian cancer cells, increasing their proliferation.

Expression and prognostic value of the cell-cycle regulatory proteins, Rb, p16MTS1, p21WAF1, p27KIP1, cyclin E, and cyclin D2, in ovarian cancer

To investigate the role of cell-cycle regulatory proteins in ovarian cancer, we performed immunohistochemistry for the cell-cycle promoters cyclin E and cyclin D2 and the cell-cycle inhibitors, Rb, p16MTS1, p21WAF1, and p27 KIP1, in 93 ovarian carcinomas (77 with follow-up data). The results were correlated with clinicopathological parameters and the prognostic value was determined by multivariate analysis. Strong Rb and moderate-high cyclin E immunoreactivity in carcinomas were weakly associated with high expression of the proliferation marker Ki67. By Cox's multivariate analysis, advanced stage (p=0.013), strong Rb expression (p=0.006), and negative-weak p21 staining (p=0.011) were independent prognostic indicators of short overall survival, indicating an apparently paradoxical role of the retinoblastoma protein in these tumors. In addition, trends pointing to an association of higher age (p=0.067) and positive cyclin E immunoreactivity (p=0.093) with an unfavorable prognosis were observed.

Effects of p16 gene on biological behavious in hepatocellular carcimoma cells

AIM: To investigate the effects of p16 gene on biological behavious in hepatocellular carcinoma cells.

METHODS: HCC cell lines SNU-449 and HepG2.2.15 were infected respectively by a replication defective, recombinant retrovirus capable of producing a high level of p16 protein expression (pCLXSN-p16). G418 resistant stable p16 protein expression cell lines were selected. And the biological behaviours of the p16 gene transfected HCC cells were observed.

RESULTS: Initial in vitro experiments in HCC cell line SNU-449 with loss of p16 protein expression demonstrated the pCLXSN-p16 treatment significantly inhibited cell growth. But there was no treatment effect when the pCLXSN-p16 was used in another HCC cell line HepG2.2.15 which has positive p16 protein expression. Subsequent study in a nude mouse model demonstrated that the p16 gene transfected SNU-449 had a lower succeeding rate in the first time establishment of tumors and grew more slowly in the nude mice when compared with non-transfected SNU-449. Moreover, the nude mice inoculated with transfected SNU-449 had a longer surviving time than those inoculated with non-transfected SNU-449.

CONCLUSION: Our results show that the p16INK4a gene transfer can inhibit the proliferation and reduce the invasion ability of hepatocellular carcinoma.

Adenovirus-mediated N5 gene transfer inhibits tumor growth and metastasis of human carcinoma in nude mice

The therapeutic effectiveness of cancer therapy often relies on induction of apoptotic cell death. Gene-therapy-mediated induction of apoptosis, therefore, may provide an effective means to kill cancer cells. The N5 gene encodes a death-domain-containing protein (p84N5) that can trigger atypical apoptosis from within the nucleus, suggesting it may be a candidate for use as a gene therapy for cancer. In the present study, we test the potential utility of a recombinant adenovirus designed to express the N5 gene(AdN5) for the treatment of a variety of human cancers using in vitro and animal models. In vitro, adenoviral-mediated N5 gene transfer inhibits the growth of five different tumor cell lines, but not a normal diploid fibroblast cell line. Adenoviral-mediated N5 gene transfer also reduces the growth and metastasis of primary human tumors in subcutaneous and orthotopic xenograft mouse models. Reduction in tumor cell growth in vitro and in vivo correlates with increased expression of p84N5 and induction of apoptosis. The relative sensitivity of different human cancer cells to AdN5 or Adp53 varies, suggesting that AdN5 may be effective in tumors relatively resistant to p53 gene therapy. We conclude that N5 has potential utility for the gene therapy of cancer.

Loss of expression of the p16 tumor suppressor gene is more frequent in advanced ovarian cancers lacking p53 mutations

OBJECTIVE

The aim of this study was to test the hypothesis that p53 mutations are less frequent in ovarian cancers with alterations in other genes that regulate G1 progression.

METHODS

Expression of G1 stimulatory (cyclins D1 and E, cdk4, Ki67) and inhibitory (p16, Rb, p27, p14) genes was analyzed using Western blots in 84 primary ovarian cancers and seven cell lines of known p53 mutation status. Expression of p16 and Rb also was determined using immunohistochemistry and the p16 gene was examined for homozygous deletions and mutations.

RESULTS

Loss of p16 protein was more frequent in ovarian cancers with wild-type p53. All four cell lines with wild-type p53 had lost p16 compared to only one of three with mutant p53 genes. p16 expression was absent in 34% (28/82) of primary ovarian cancers, and this was significantly more common in cases with wild-type p53 (14/28, 50%) compared to those with p53 mutations (14/54, 26%, P = 0.03). Homozygous deletion of the p16 gene was found in cell lines lacking p16, but not in any primary cancers. p16 loss was more common in serous (21/52, 40%) than nonserous cancers (4/23, 17%, P = 0.07). Cases that expressed p16 were more likely to express high levels of Rb (47/55, 85%) than p16-negative cases (12/28, 43%, P < 0.001). Loss of Rb occurred in 5/30 (17%) ovarian cancers lacking p53 mutations compared to 5/54 (9%) cases with p53 mutations (P = 0.48). Expression of G1 stimulatory proteins (cyclins D1 and E, cdk4, Ki67) did not correlate with p53 mutation status.

CONCLUSIONS

Loss of expression of the p16 tumor suppressor occurs more often in ovarian cancers lacking p53 mutations. These data are consistent with the paradigm that inactivation of p53 is less of a requisite event in ovarian carcinogenesis when another G1 regulatory gene such as p16 already has been inactivated.

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.