Invasion and subsequent metastasis is the major cause of death from most cancers including prostate cancer. Herein we report on the potential tumor suppressive properties of Rab7, a GTPase that regulates trafficking of lysosomes. The movement of lysosomes to the cell surface in response to environmental cues increases the secretion of proteinases and cell invasion. We determined that Troglitazone and other members of the Thiazolidinedione family inhibit cell-surface directed lysosome trafficking and cathepsin B secretion through a Rab7-dependent mechanism. Moreover, Rab7 shRNA expressing cells were found to be more invasive in vitro and in vivo. Increased invasiveness was accompanied by elevated expression of the c-Met receptor and prolonged downstream signaling, thereby supporting a role for Rab7 as a mediator of signaling down-regulation. Taken together, these results suggested that Rab7 acts as a negative regulator of prostate tumor growth and invasion, providing further evidence for its potential as a tumor suppressor.

Core binding factor (CBF) is a transcription factor complex that plays roles in development, stem-cell homeostasis, and human disease. CBF is a heterodimer composed of one of three DNA-binding RUNX proteins plus the non-DNA-binding protein, CBFβ. Recent studies have showed that the RUNX factors exhibit complex expression patterns in prostate, breast, and ovarian cancers, and CBF has been implicated in the control of cancer-related genes. However, the biologic roles of CBF in solid tumors have not been fully elucidated. To test whether CBF is required for the malignant phenotype of various epithelial cancers, we used lentiviral delivery of CBFβ-specific shRNA to significantly decrease CBFβ expression in two prostate cancer cell lines (PPC1 and PC-3) and the SKOV-3 ovarian cancer cell line. We found that knockdown of CBFβ significantly inhibited anchorage independent growth of each cell line. Further, CBFβ knockdown in PPC1 cells suppressed xenograft tumor growth compared to controls. Mice injected with SKOV-3 ovarian cancer cells knocked-down for CBFβ exhibited a survival time similar to control mice. However, human cells recovered from the ascites fluid of these mice showed CBFβ expression levels similar to those from mice injected with control SKOV-3 cells, suggesting that CBFβ knockdown is incompatible with tumor cell growth. Gene expression profiling of CBFβ knockdown cells revealed significant changes in expression in genes involved in various developmental and cell signaling pathways. These data collectively suggest that CBFβ is required for malignancy in some human cancers.

Background Lynch syndrome is a rare familial cancer syndrome caused by pathogenic variants in the mismatch repair genes MLH1, MSH2, MSH6, or PMS2, that cause predisposition to various cancers, predominantly colorectal and endometrial cancer. Data are emerging that pathogenic variants in mismatch repair genes increase the risk of earlyonset aggressive prostate cancer. The IMPACT study is prospectively assessing prostate-specific antigen (PSA) screening in men with germline mismatch repair pathogenic variants. Here, we report the usefulness of PSA screening, prostate cancer incidence, and tumour characteristics after the first screening round in men with and without these germline pathogenic variants. MethodsThe IMPACT study is an international, prospective study. Men aged 40-69 years without a previous prostate cancer diagnosis and with a known germline pathogenic variant in the MLH1, MSH2, or MSH6 gene, and age-matched male controls who tested negative for a familial pathogenic variant in these genes were recruited from 34 genetic and urology clinics in eight countries, and underwent a baseline PSA screening. Men who had a PSA level higher than 3•0 ng/mL were offered a transrectal, ultrasound-guided, prostate biopsy and a histopathological analysis was done. All participants are undergoing a minimum of 5 years' annual screening. The primary endpoint was to determine the incidence, stage, and pathology of screening-detected prostate cancer in carriers of pathogenic variants compared with non-carrier controls. We used Fisher's exact test to compare the number of cases, cancer incidence, and positive predictive values of the PSA cutoff and biopsy between carriers and non-carriers and the differences between disease types (ie, cancer vs no cancer, clinically significant cancer vs no cancer). We assessed screening outcomes and tumour characteristics by pathogenic variant status. Here we present results from the first round of PSA screening in the IMPACT study. This study is registered with ClinicalTrials.gov, NCT00261456, and is now closed to accrual.

Human prostate tumor vaccine and gene therapy trials using ex vivo methods to prime dendritic cells (DCs) with prostate specific membrane antigen (PSMA) have been somewhat successful, but to date the lengthy ex vivo manipulation of DCs has limited the widespread clinical utility of this approach. Our goal was to improve upon cancer vaccination with tumor antigens by delivering PSMA via a CD40-targeted adenovirus vector directly to DCs as an efficient means for activation and antigen presentation to T-cells. To test this approach, we developed a mouse model of prostate cancer by generating clonal derivatives of the mouse RM-1 prostate cancer cell line expressing human PSMA (RM-1-PSMA cells). To maximize antigen presentation in target cells, both MHC class I and TAP protein expression was induced in RM-1 cells by transduction with an Ad vector expressing interferon-gamma (Ad5-IFNγ). Administering DCs infected ex vivo with CD40-targeted Ad5-huPSMA, as well as direct intraperitoneal injection of the vector, resulted in high levels of tumor-specific CTL responses against RM-1-PSMA cells pretreated with Ad5-IFNγ as target cells. CD40 targeting significantly improved the therapeutic antitumor efficacy of Ad5-huPSMA encoding PSMA when combined with Ad5-IFNγ in the RM-1-PSMA model. These results suggest that a CD-targeted adenovirus delivering PSMA may be effective clinically for prostate cancer immunotherapy.

TLKs appear to be intimately linked to the pattern of resistance to DNA damage, and specifically DSBs, a finding that was not reported before for any cell lines, and certainly not systematically for human prostate cell lines.