Retinoblastoma (RB; encoded by RB1) is a tumor suppressor that is frequently disrupted in tumorigenesis and acts in multiple cell types to suppress cell cycle progression. The role of RB in tumor progression, however, is poorly defined. Here, we have identified a critical role for RB in protecting against tumor progression through regulation of targets distinct from cell cycle control. In analyses of human prostate cancer samples, RB loss was infrequently observed in primary disease and was predominantly associated with transition to the incurable, castration-resistant state. Further analyses revealed that loss of the RB1 locus may be a major mechanism of RB disruption and that loss of RB function was associated with poor clinical outcome. Modeling of RB dysfunction in vitro and in vivo revealed that RB controlled nuclear receptor networks critical for tumor progression and that it did so via E2F transcription factor 1-mediated regulation of androgen receptor (AR) expression and output. Through this pathway, RB depletion induced unchecked AR activity that underpinned therapeutic bypass and tumor progression. In agreement with these findings, disruption of the RB/E2F/nuclear receptor axis was frequently observed in the transition to therapy resistance in human disease. Together, these data reveal what we believe to be a new paradigm for RB function in controlling prostate tumor progression and lethal tumor phenotypes. IntroductionRetinoblastoma (RB; encoded by RB1), a tumor suppressor protein, is a critical negative regulator of tumor development. RB prevents tumorigenesis by suppressing cell cycle progression (1). However, the role of RB in tumor progression is poorly understood, and the clinical importance of RB loss during this process has not been well considered. Here, we identified a clinically relevant function for RB in tumor progression, manifest through control of hormone signaling networks.The function of RB in cell cycle control has been well described (1). Conditions favoring cell cycle arrest induce RB hypophosphorylation and activation. Active RB binds to promoters of genes required for S-phase entry (e.g., CCNA2 and MCM7) and, through association with the SWI/SNF complex and corepressor molecules (e.g., Sin3B), elicits transcriptional corepression. Many RB target genes are positively regulated by activator E2F transcription factors, supporting the current model that RB acts by suppressing E2F-mediated transcriptional activation. Indeed, the minimal transcriptional repression and tumor suppression domain of RB contains the E2F binding motif. E2F-independent functions of RB have been identified (2), but the contribution of these functions to tumor suppression is uncertain. Thus, contemporary views of RB suggest that the protein prevents cell cycle deregulation and tumor development through suppression of activator E2Fs.

The retinoblastoma tumor suppressor protein (RB), a critical mediator of cell cycle progression, is functionally inactivated in the majority of human cancers, including prostatic adenocarcinoma. The importance of RB tumor suppressor function in this disease is evident because 25% to 50% of prostatic adenocarcinomas harbor aberrations in RB pathway. However, no previous studies challenged the consequence of RB inactivation on tumor cell proliferation or therapeutic response. Here, we show that RB depletion facilitates deregulation of specific E2F target genes, but does not confer a significant proliferative advantage in the presence of androgen. However, RB-deficient cells failed to elicit a cytostatic response (compared with RB proficient isogenic controls) when challenged with androgen ablation, AR antagonist, or combined androgen blockade. These data indicate that RB deficiency can facilitate bypass of first-line hormonal therapies used to treat prostate cancer. Given the established effect of RB on DNA damage checkpoints, these studies were then extended to determine the impact of RB depletion on the response to cytotoxic agents used to treat advanced disease. In this context, RB-deficient prostate cancer cells showed enhanced susceptibility to cell death induced by only a selected subset of cytotoxic agents (antimicrotubule agents and a topoisomerase inhibitor). Combined, these data indicate that RB depletion dramatically alters the cellular response to therapeutic intervention in prostate cancer cells and suggest that RB status could potentially be developed as a marker for effectively directing therapy. [Cancer Res 2007;67(13):6192-203]

Virtual surgical planning, patient-specific virtually pre-contoured plate template and 3D printing technology improve the outcomes of acetabular fracture surgery by reducing duration and invasiveness of surgery and improving the quality of reduction. However, studies with larger sample size are required to further validate it.

Patient-specific pre-contoured plate made using 3D model is a better implant than intra-operatively contoured plate. Real-time 3D pelvis model is an accurate technique for pre-operative planning in acetabular fractures.

Factors that drive prostate cancer progression remain poorly defined, thus hindering the development of new therapeutic strategies. Disseminated tumors are treated through regimens that ablate androgen signaling, as prostate cancer cells require androgen for growth and survival. However, recurrent, incurable tumors that have bypassed the androgen requirement ultimately arise. This study reveals that the Brm ATPase, a component of selected SWI/SNF complexes, has significant antiproliferative functions in the prostate that protect against these transitions. First, we show that targeted ablation of Brm is causative for the development of prostatic hyperplasia in mice. Second, in vivo challenge revealed that Brm−/− epithelia acquire the capacity for lobe-specific, castration-resistant cellular proliferation. Third, investigation of human specimens revealed that Brm mRNA and protein levels are attenuated in prostate cancer. Fourth, Brm down-regulation was associated with an increased proliferative index, consistent with the mouse model. Lastly, gene expression profiling showed that Brm loss alters factors upstream of E2F1; this was confirmed in murine models, wherein Brm loss induced E2F1 deregulation in a tissue-specific manner. Combined, these data identify Brm as a major effector of serum androgen–induced proliferation in the prostate that is disrupted in human disease, and indicate that loss of Brm confers a proliferative advantage in prostate cancer.