Expression of the retinoblastoma-related gene Rb2/p130 in the pathogenesis of serous carcinoma of the ovary.

OBJECTIVE: The purpose of this study was to evaluate the immunohistochemical Rb2/p130 expression in a series of benign, borderline, and malignant ovarian tumors. STUDY DESIGN: Seventy-six operative specimens were analyzed. Frequencies and percents were calculated for variables by each of the 5 disease stage groups in increasing severity and again for the disease stage groups collapsed into benign (serous cystadenoma or endosalpingosis), low-grade [serous borderline tumors (SBT) or low-grade serous carcinoma (LGSC)] and high-grade serous carcinoma. RESULTS: There was no loss of expression in benign serous cystadenomas (0/18). Ten percent of SBT's (2/20), 47% of LGSC's (9/19), and 16% of HGSC's (3/16) had loss of expression. There was a significant difference in the expression during the progression from cystadenoma to SBT to LGSC. CONCLUSIONS: Loss of Rb2/p130 expression is a rare event in benign cystadenoma. The progression to LGSC is associated with a decrease in gene expression.

Downregulation and aberrant promoter methylation of p16INK4A: a possible novel heritable susceptibility marker to retinoblastoma.

RB loss has long been recognized as the causative genetic alteration underlying retinoblastoma but it is increasingly evident that other alterations are required for the tumor to develop. Therefore, we set out to identify additional inheritable susceptibility markers and new potential preventive and therapeutic targets for retinoblastoma. We focused on the p16INK4A tumor suppressor gene because of its possible role in retinoblastoma pathogenesis and its involvement in predisposition to familial cancer. p16INK4A expression was analyzed in tumor samples from retinoblastoma patients by immunohistochemistry and in peripheral blood cells from both patients and their parents by real-time quantitative reverse transcription-PCR (qRT-PCR). Since promoter methylation is a common mechanism regulating p16INK4A expression, the methylation status of its promoter was also analyzed in blood samples from patients and their parents by methylation-specific PCR. A downregulation of p16INK4A was observed in 55% of retinoblastoma patients. Interestingly, in 56% of the cases showing p16INK4A downregulation at least one of the patients' parents bore the same alteration in blood cells. Analysis of p16INK4A promoter methylation showed hypermethylation in most patients with p16INK4A downregulation and in the parents with the same alteration in p16INK4A expression. The finding that p16INK4A was downregulated both in patients and their parents suggests that this alteration could be a novel inheritable susceptibility marker to retinoblastoma. The observation that p16INK4A downregulation seems to be due to its promoter hypermethylation opens the way for the development of new preventive and therapeutic strategies using demethylating agents.

Novel p53/p130 axis in bladder tumors.

OBJECTIVES: To identify the relationships between key components of the proliferative and apoptotic pathways in bladder tumors. METHODS: A tissue array of 88 bladder tumors was assembled. Immunohistochemical analyses were used to investigate the relationship between nine different parameters: stage, proliferation (Ki67), apoptosis (in situ DNA nick end labeling), the anti-apoptotic protein Bcl-2, tumor suppressors p53 and retinoblastoma protein (Rb), the Rb-related protein p130, cyclin E, and the cyclin-dependent kinase inhibitor p27. The protein expression in each tumor was reported as the percentage of positively staining cells. RESULTS: The analysis focused on Stage 1 to 3 tumors. Analysis found that p53 expression increased progressively with stage, and Rb and p27 decreased with increasing stage. Overall, the cyclin E levels correlated with the proliferative index. Cyclin E levels were low in Stage 1 tumors and elevated in Stage 2 tumors, but were decreased in Stage 3 tumors. Multivariate analysis uncovered a correlation between cyclin E and proliferation (Ki67) and a weak correlation between p53 and Bcl-2 and between p27 and Rb. A strong correlation was found between the expression of p53 and p130, which was apparent in Stages 1 and 3, but not in Stage 2. Furthermore, high levels of p130 protein were detected primarily in the cytoplasm. CONCLUSIONS: These results suggest a novel p53/p130 axis in bladder tumors.

Immunohistochemical analysis of pRb2/p130, VEGF, EZH2, p53, p16(INK4A), p27(KIP1), p21(WAF1), Ki-67 expression patterns in gastric cancer.

Although the considerable progress against gastric cancer, it remains a complex lethal disease defined by peculiar histological and molecular features. The purpose of the present study was to investigate pRb2/p130, VEGF, EZH2, p53, p16(INK4A), p27(KIP1), p21(WAF1), Ki-67 expressions, and analyze their possible correlations with clinicopathological factors. The expression patterns were examined by immunohistochemistry in 47 patients, 27 evaluated of intestinal-type, and 20 of diffuse-type, with a mean follow up of 56 months and by Western blot in AGS, N87, KATO-III, and YCC-2, -3, -16 gastric cell lines. Overall, stomach cancer showed EZH2 correlated with high levels of p53, Ki-67, and cytoplasmic pRb2/p130 (P < 0.05, and P < 0.01, respectively). Increased expression of EZH2 was found in the intestinal-type and correlated with the risk of distant metastasis (P < 0.05 and P < 0.01, respectively), demonstrating that this protein may have a prognostic value in this type of cancer. Interestingly, a strong inverse correlation was observed between p27(KIP1) expression levels and the risk of advanced disease and metastasis (P < 0.05), and a positive correlation between the expression levels of p21(WAF1) and low-grade (G1) gastric tumors (P < 0.05), confirming the traditionally accepted role for these tumor-suppressor genes in gastric cancer. Finally, a direct correlation was found between the expression levels of nuclear pRb2/p130 and low-grade (G1) gastric tumors that was statistically significant (P < 0.05). Altogether, these data may help shed some additional light on the pathogenetic mechanisms related to the two main gastric cancer histotypes and their invasive potentials.

Immunohistochemical evaluation of pRb2/p130, VEGF, EZH2, p53, p16, p21waf-1, p27, and PCNA in Barrett's esophagus.

Control of the G1/S-phase transition as well as angiogenic switch are two of the most studied mechanisms in cancer. The current study examined the correlation between the immunohistochemical expression of pRb2/p130, VEGF, EZH2, p53, p16, p21waf-1, p27, and PCNA in Barrett's esophagus (BE). Overall, p53 showed a much higher expression in BE patients (up to 50%) than in controls (1-10%) (P < 0.005). Also p21 showed a downregulation in BE when compared to normal esophagus (70% of cells vs. 65%), but the difference did not show any statistical significance (P = 0.45). pRb2/p130 was detected in 80% of cells in normal controls, but showed positive in only 20% of cells in BE biopsies. Additionally, Rb2/p130 expression was inversely correlated to that of VEGF, EZH2, and PCNA (P < 0.0001, P = 0.0032, P < 0.001, respectively). p27 stained more intensely and in a widespread manner (70%) cells in normal esophageal tissues but about only 30% in BE samples (P < 0.001). Lastly, in accordance with other reports, we also found p16 expressed by immunohistochemistry at high levels in normal controls and at low levels in BE (P < 0.001). In conclusion, p16, p21, p27, and p53 staining confirmed previously published data. Interestingly, pRb2/p130 expression was found significantly decreased in metaplastic epithelium compared to normal controls and showed significant inverse correlation with the expression of other markers, such as VEGF, EZH2, and PCNA. These data, taken together, indicate that these molecular events occurring in Barrett's metaplasia (BM) may represent one of the many steps taking place during esophageal malignant progression such as impairment of cell-cycle control, altered differentiation, and unbalanced angiogenesis.

pRb2/p130 and VEGF expression in endometrial carcinoma in relation to angiogenesis and histopathologic tumor grade.

PURPOSE: Endometrial cancer is the most common gynecologic malignancy. Established prognostic factors are histologic grade, depth of myometrial invasion, and extrauterine spread including retroperitoneal lymph node metastases. Tumorigenesis is a multistep process involving different genetic changes resulting in uncontrolled cellular proliferation, inhibition of apoptosis, and enhanced vascular proliferation among other events. Angiogenesis, the formation of new blood vessels from a preexisting vascular network, is necessary for invasive tumor growth and metastasis and constitutes an important point in the control of cancer progression. The pathogenesis of the angiogenetic phenotype may involve the inactivation of different tumor suppressor genes. EXPERIMENTAL DESIGN: We investigated the relationship between the expression levels of VEGF and the retinoblastoma family member pRb2/p130 in endometrial carcinoma in relation to histopathologic tumor grade in a cohort of 50 patients. RESULTS: We found that VEGF and pRB2/p130 expression were inversely correlated. Additionally, high grade tumors presented a significantly lower number of cells expressing pRb2/p130 when compared to low grade tumors. A significant positive correlation was found, by means of the Spearman coefficient, between VEGF expression and binary grading (0.450, p-value < 0.005) which is an architectural grading system that uses low-magnification assessment of amount of solid growth, pattern of invasion, and presence of necrosis to divide endometrioid carcinomas into low- and high-grade tumors. Additionally, we also found a negative correlation between pRb2/p130 expression levels and binary grading (-0.595, p-value < 0.005). Interestingly, we also found that VEGF and pRb2/p130 expression levels were not related to staging (p-value > 0.005). CONCLUSIONS: These results open up a new perspective including novel markers that, combined together, may be useful in patient screening for endometrial cancer aggressiveness.