5925

RB1

retinoblastoma 1;RB1;retinoblastoma 1

prepro-retinoblastoma-associated protein|protein phosphatase 1, regulatory subunit 130|retinoblastoma suspectibility protein|retinoblastoma-associated protein

13q14.2

protein-coding

OBJECTIVE: (1) To investigate the promoter methylation status of gene p16(INK4a) and gene RB in breast carcinoma and the adjacent non-neoplastic hyperplastic epithelial tissue. (2) To study the correlation of p16(INK4a) gene expression at protein level with the abnormal gene methylation, the clinical manifestation and the pathological parameters. METHODS: Methylation status of promoters of p16(INK4a) gene and RB gene was detected by using methylation specific PCR in 46 cases of breast cancer, 22 cases of the adjacent non-neoplastic hyperplastic epithelium tissue and 7 cases of normal breast tissue. In addition, the p16(INK4a) gene protein expression level was also detected using immunohistochemical technique(SP method) in 46 cases of breast cancer and 22 cases of the adjacent hyperplastic epithelial tissue. RESULTS: The methylation rate of p16(INK4a) gene was 23.9% (11/46) in breast cancer, 18.2% (4/22) in the adjacent non-neoplastic hyperplastic epithelial tissue and 1/7 in normal breast tissue, respectively. The methylation rate of RB gene was relatively low, which was 10.8% (5/46), 9.1% (2/22) and 0(0/7) in the above 3 groups, respectively. Methylation rate of p16(INK4a) gene and RB gene was not significantly different among the breast cancer, the adjacent non-neoplastic hyperplastic tissue and the normal tissues (P > 0.05). However, the methylation status of p16(INK4a) gene was closely correlated with its protein expression level and the negative ER expression result of the breast cancer (P < 0.05), but not correlated with the size of the cancer, differentiation status, lymph node metastasis, and age. The methylation status of RB gene was correlated with lymph node metastasis, but not with the size, the differentiation status, ER expression of the breast cancer and the age of the patients. CONCLUSIONS: The abnormal methylation of p16(INK4a) gene may not play a significant role in the early stage of breast cancinogenesis, but may play a role of in the progression of the cancer. RB gene methylation may also be a indicator in choice to identify the progression and prognosis of breast cancer.

Germline mutations affecting the retinoblastoma gene (RB1) predispose to inherited retinoblastomas but also other malignancies, including breast cancer. While somatic RB1 mutations have been detected in different malignancies, information about the potential role of RB1 mutations in breast cancer is limited. Recently, we discovered RB1 mutations to be associated with resistance to anthracyclines/mitomycin in primary breast cancer. The present work is the first report evaluating RB1 mutation and epigenetic status in metastatic breast cancer. Among 148 breast cancer samples analyzed by MLPA, four samples harbored intragenic deletions/duplications: Thus, exons 1-2 were deleted in two tumors and exons 21-23 in one tumor, while one sample harbored duplication of exons 18-23. The entire RB1 gene was duplicated in two tumors and multiple amplifications were revealed in one sample. Reduced copy number was observed in 17 samples (11.5%). No point mutation or promoter hypermethylation was discovered (n = 38 and 114 tumors analyzed, respectively). Interestingly, among seven tumors expressing lack of response to epirubicin, two samples harbored alterations in RB1, contrasting none out of 16 tumors with stable disease or an objective response (P = 0.08). In summary, the frequency of RB1 alterations in metastatic lesions was not increased when compared to primary breast cancer, indicating that RB1 alterations do not play a major role in metastatic development. While a non-significant association suggesting RB1 alterations to be linked to therapy resistance was observed, our data do not suggest a major role for RB1 alterations explaining acquired drug resistance.

BACKGROUND: Although integrins have been implicated in the progression of breast cancer, the exact mechanism whereby they exert this regulation is clearly not understood. To understand the role of integrins in breast cancer, we examined the expression levels of several integrins in mouse breast cancer cell lines by flow cytometry and the data were validated by Western and RT-PCR analysis. The importance of integrins in cell migration and cell invasion was examined by in vitro assays. Further the effect of integrins on metastasis was investigated by in vivo experimental metastasis assays using mouse models. RESULTS: Integrin alpha5 subunit is highly expressed in the nonmetastatic cell line 67NR and is significantly low in the highly invasive cell line 4T1. In contrast, expression levels of integrin alpha6 subunit are high in 4T1 cells and low in 67NR cells. In vitro data indicated that overexpression of alpha5 subunit and knockdown of alpha6 integrin subunit inhibited cell proliferation, migration, and invasion. Our in vivo findings indicated that overexpression of integrin alpha5 subunit and knockdown of alpha6 subunit decreased the pulmonary metastasis property of 4T1 cells. Our data also indicated that overexpression of alpha 5 integrin subunit and suppression of alpha6 integrin subunit inhibited cells entering into S phase by up-regulating p27, which results in downregulation of cyclinE/CDK2 complexes, This suggests that these integrins regulate cell growth through their effects on cell-cycle-regulated proteins. We also found that modulation of these integrins upregulates E2F, which may induce the expression of chk1 to regulate cdc25A/cyclin E/CDK2/Rb in a feedback loop mechanism. CONCLUSION: This study indicates that Integrin alpha5 subunit functions as a potential metastasis suppressor, while alpha6 subunit functions as a metastasis promoter. The modulation of integrins reduces cdc25 A, another possible mechanism for downregulation of CDK2. Taken together we demonstrate a link between integrins and the chk1-cdc25-cyclin E/CDK2-Rb pathway.

This paper investigates the association between protein retinoblastoma (pRB) loss and the T,N stage and prognosis in esophageal squamous cell carcinomas (ESCCs) using meta-analysis. We conducted a meta-analysis of 16 studies, comprising 1,117 patients to clarify this issue. All the studies searched by the electronic literature PubMed and http://www.KJEBM.com, which had been published during the period from January 1996 to January 2012 according to the inclusion criteria. Summary odds ratios (OR) were calculated using fixed or random-effects models. The summary odds ratios (ORs) for pRB inactive were 0.64 (95% confidence interval [CI]:0.45-0.91, P = 0.01) for T1/T2 versus T3/T4 tumors; summary OR = 0.69 (95% CI:0.51-0.94, P = 0.02) for N0 versus N1 tumors. The association between pRB loss and prognosis was examined in nine studies, and the summary hazard ratio was 1.39 (95% CI:1.11-1.74, P = 0.004). pRB inactive was significant associated with T3/T4 tumors and N1 stage as well as adverse prognosis for ESCCs. It appears warranted to prospectively validate that pRB loss may be used for subdividing the T,N stage evaluation of patients with ESCCs, and these patients may be the preponderant people for individualized treatment or target therapy.

A series of 76 cases of gastrointestinal tract endocrine tumors, including 21 poorly differentiated endocrine carcinomas (PDECs, small cell carcinomas) and 55 well-differentiated endocrine neoplasms (WDENs, carcinoids), 18 metastatic and 37 nonmetastatic rectal carcinoids, were examined by immunohistochemical analysis for p16INK4a, cyclin D1, and retinoblastoma protein (pRB) expression. Overexpression of p16INK4a was noted in 16 (76%) of the PDECs and none of the WDENs (P < .0001). Loss of pRB expression was demonstrated in 14 (67%) of the PDECs and 17 (31%) of the WDENs (P = .004). Overexpression of cyclin D1 was noted in 49 (89%) of the WDENs and 3 (14%) of the PDECs (P < .0001). Loss of pRB expression was noted in 11 (61%) of 18 metastatic WDENs and only 6 (16%) of 37 nonmetastatic WDENs (P = .001). The p16INK4a/cyclin D1/pRB pathway was altered in gastrointestinal tract endocrine tumors, and the loss of expression of pRB may be helpful in identifying patients at high risk of metastasis in rectal WDENs.

Our recent comparative genomic hybridization (CGH) study has shown that losses of the long arm of chromosome 13 were the most common aberrations in primary larynx tumors and their corresponding metastases. In the present study, 20 pairs of primary larynx tumors and their metastases were analyzed by interphase fluorescence in situ hybridization (FISH) with three different 13q-specific probes (RB1, D13S25, and 13qtel). Our experiments were generally consistent with the CGH results, with some differences indicating cell population heterogeneity in the analyzed cohort of tumors. The results provided further evidence for the putative role of the RB1 gene alterations in the metastatic process, although a contribution by other gene(s) during metastasis cannot be ruled out.

The immunohistochemical expression of cell cycle proteins p16, cyclin D1, and pRb was assessed in 112 benign and malignant melanocytic tumors and correlated with tumor progression, prognosis, and outcome. Comparing benign and malignant tumors, there were significant differences in the median score for all 3 proteins, with decreased p16 (P = .000001), increased cyclin D1 (P = .01), and increased pRb in melanomas (P = .01). There was a progressive loss of expression of p16 with progression from benign naevi to primary melanomas and to metastases. p16 was significantly decreased in primary tumors from melanoma patients who developed recurrent disease (P = .0000013). Cyclin D1 and pRb showed a progressive increase in expression from benign to malignant tumors but with relative decreases in the more advanced tumors (thick primaries and metastatic melanomas). Alterations in cell cycle proteins involved in G1/S transition are implicated in melanocytic tumor progression and have a potential role in diagnosis and prognostication.

Osteosarcoma is a malignant bone tumor with high metastatic potential. metastasis at diagnosis is the most significant prognostic factor in predicting the clinical outcome of osteosarcoma. We compared the gene expression of metastases that were present at the time of initial diagnosis to those developed later in the course of the disease. We used quantitative real-time polymerase chain reaction to evaluate the gene expression of MDM2, CXCR4, RANKL, RB1, and OSTERIX in 98 samples of osteosarcoma taken from 47 patients (74 metastases and 24 primary tumors) and 30 nonmalignant lung tissues surrounding osteosarcoma metastases. In addition, we investigated the copy number changes of RB1 and MDM2 genes in 12 primary cultures of pulmonary metastases of osteosarcoma, using interphase fluorescence in situ hybridization. Metastases from metastatic patients at diagnosis were characterized by low expression of RB1 and RANKL (P = .0009 and P = .0109, respectively) and overexpression of CXCR4 and MDM2 (P = .0389 and P = .0325, respectively). The loss of RANKL and gain of CXCR4 could also be detected in the primary tumors of metastatic patients at diagnosis (P = .0121 and P = .0264, respectively). Thus, some early genetic events such as the loss of RANKL and the gain of CXCR4 expressions probably facilitate the metastatic progression concomitant with the primary tumor establishment, supporting the role of the CXCR4 receptor in directing osteosarcoma metastases to the lung. On the other hand, late events such as the loss of RB1 and gain of MDM2, crucial regulators of cell cycle, appear to be related to the final mechanisms contributing to the metastatic establishment of osteosarcoma.

Interactions between the cyclin-dependent kinase inhibitors (CDKI) and human papillomavirus (HPV) infection in the pathogenesis of vulvar carcinoma are still incomplete. This study aimed to evaluate the prognostic relevance of these proteins in vulvar cancer. One hundred and thirty-nine patient specimens assembled in a tissue microarray were evaluated for p16, p21, p27, and pRb by immunohistochemistry. HPV status was assessed by a linear array HPV genotyping test. In 16 cases with available frozen tumor, quantitative real-time reverse transcriptase-polymerase chain reaction for CDKN2A(p16), CDKN1A, and Rb was performed. Protein expression was considered positive in 40 patients for p16, 35 for p21, 28 for p27, and 19 for pRb. HPV was positive in 43 of the 105 evaluable cases. expression of CDKIs and pRb, with the exception of p16, seem to be linked to the early phases of vulvar carcinogenesis. Although p16 and p21 protein expression was associated with early stages of disease, no prognostic significance was found when analyzing CDKI proteins or detecting HPV status, limiting their clinical usage. No association was observed between expression of CDKI proteins and HPV status, suggesting that in spite of this association found in cervical cancer, this seems not to be valid for vulvar carcinoma.