Highlighting recent treatment advances in metastatic prostate cancer: expanding the treatment arsenal

The Effect of Androgen Deprivation Therapy on the Cardiovascular System in Advanced Prostate Cancer

Androgen deprivation therapy (ADT) is a mainstay treatment for metastatic prostate cancer, improving progression-free survival. ADT suppresses the production of testosterone and reduces circulating levels of the hormone. Luteinizing hormone-releasing hormone (LH-RH) agonists are the most commonly used ADT modality. They can be given alone or in combination with androgen synthesis inhibitors or androgen receptor antagonists. An estimated 40% of prostate cancer patients will receive ADT as part of their therapy during their lifetime. However, ADT has numerous adverse effects, including an increased cardiovascular risk that impacts quality of life. Relugolix is an alternative form of ADT. It is the only oral gonadotropin-releasing hormone antagonist, circumventing injection site reactions, making it easier for patients to take, and thus increasing compliance. Testosterone suppression with relugolix is excellent and testosterone recovery after discontinuation is rapid. This paper reviews the ADT and anti-androgen treatment options for men with prostate cancer and the cardiovascular effects of these therapies. There is accumulating evidence that cardiovascular risk with relugolix is lower than with other ADT medications and also lower than with androgen synthesis inhibitors and androgen receptor antagonists. This paper provides insight into the use of different ADT regimens based on the cardiovascular status and circumstances. It explores strategies to mitigate negative cardiovascular consequences and highlights the need for further study.

Gene expression signature of castrate resistant prostate cancer

Prostate gland is a highly androgen dependent gland and hence the first line of treatment for metastatic prostate cancer happens to be androgen ablation. This is achieved by multiple non-surgical methods. However, most of these cancers although respond well initially, become resistant to androgen ablation sooner or later. These cancers then become extremely aggressive and difficult to treat, thereby drastically affect the patient prognosis. Identification of a gene expression signature for castrate resistant prostate cancer may aid in identification of mechanisms responsible for castrate resistance, which in turn would help in better management of the disease. METHODS: Patient samples belonging to a. Control group; b. Castrate Sensitive group and c. Castrate Resistant group were collected. Gene expression profiling was performed on these samples using RNA-seq. Differentially expressed genes between control and castrate sensitive as well as control and castrate resistant groups were identified. This data was compared with data from The Cancer Genome Atlas (TCGA) in order to get relevance in prognosis. RESULTS: We have identified 481 differentially expressed genes between control and castrate sensitive groups; and 446 genes differentially expressed between control and castrate resistant groups. We have also identified 364 genes which are expressed in the castrate resistant group alone, which is of interest since these may have an implication in evolution of castrate resistance and also prognosis. When compared to prostate cancer data from TCGA, 763 genes were found in common to our dataset. With this, a CaS and CaR signature was defined. Using criteria such as overall survival, disease-free survival, progression-free survival and biochemical recurrence, we have identified genes that may have relevance in progression to castrate resistance and in prognosis. Functional annotation of these genes may give an insight into the mechanism of development of castrate resistance.

Glucocorticoid Receptor and β-Catenin Interact in Prostate Cancer Cells and Their Co-Inhibition Attenuates Tumorsphere Formation, Stemness, and Docetaxel Resistance

Therapy resistance hinders the efficacy of anti-androgen therapies and taxane-based chemotherapy for advanced prostate cancer (PCa). Glucocorticoid receptor (GR) signaling mediates resistance to androgen receptor signaling inhibitors (ARSI) and has also been recently implicated in PCa resistance to docetaxel (DTX), suggesting a role in therapy cross-resistance. Like GR, β-catenin is upregulated in metastatic and therapy-resistant tumors and is a crucial regulator of cancer stemness and ARSI resistance. β-catenin interacts with AR to promote PCa progression. Given the structural and functional similarities between AR and GR, we hypothesized that β-catenin also interacts with GR to influence PCa stemness and chemoresistance. As expected, we observed that treatment with the glucocorticoid dexamethasone promotednuclear accumulation of GR and active β-catenin in PCa cells. Co-immunoprecipitation studies showed that GR and β-catenin interact in DTX-resistant and DTX-sensitive PCa cells. Pharmacological co-inhibition of GR and β-catenin, using the GR modulator CORT-108297 and the selective β-catenin inhibitor MSAB, enhanced cytotoxicity in DTX-resistant PCa cells grown in adherent and spheroid cultures and decreased CD44+/CD24- cell populations in tumorspheres. These results indicate that GR and β-catenin influence cell survival, stemness, and tumorsphere formation in DTX-resistant cells. Their co-inhibition could be a promising therapeutic strategy to overcome PCa therapy cross-resistance.

The LEDGF/p75 Integrase Binding Domain Interactome Contributes to the Survival, Clonogenicity, and Tumorsphere Formation of Docetaxel-Resistant Prostate Cancer Cells

Patients with prostate cancer (PCa) receiving docetaxel chemotherapy invariably develop chemoresistance. The transcription co-activator lens epithelium-derived growth factor p75 (LEDGF/p75), also known as DFS70 and PSIP1, is upregulated in several human cancers, including PCa and promotes resistance to docetaxel and other drugs. The C-terminal region of LEDGF/p75 contains an integrase binding domain (IBD) that tethers nuclear proteins, including the HIV-1 integrase and transcription factors, to active chromatin to promote viral integration and transcription of cellular survival genes. Here, we investigated the contribution of the LEDGF/p75 IBD interactome to PCa chemoresistance. Quantitative immunoblotting revealed that LEDGF/p75 and its IBD-interacting partners are endogenously upregulated in docetaxel-resistant PCa cell lines compared to docetaxel-sensitive parental cells. Using specific human autoantibodies, we co-immunoprecipitated LEDGF/p75 with its endogenous IBD-interacting partners JPO2, menin, MLL, IWS1, ASK1, and PogZ, as well as transcription factors c-MYC and HRP2, in docetaxel-resistant cells, and confirmed their nuclear co-localization by confocal microscopy. Depletion of LEDGF/p75 and selected interacting partners robustly decreased the survival, clonogenicity, and tumorsphere formation capacity of docetaxel-resistant cells. These results implicate the LEDGF/p75 IBD interactome in PCa chemoresistance and could lead to novel therapeutic strategies targeting this protein complex for the treatment of docetaxel-resistant tumors.