Screening and molecular characterization of epigenetics and DNA repair inhibitors as radiosensitizers in prostate cancer.

Different treatment options are available for newly diagnosed PC patients. For hormone na?ve PC first line treatment consists of surgery (prostatectomy) or radiotherapy combined with androgen deprivation therapy (ADT) (4). These treatments are generally curative and results in decreased prostate specific antigen (PSA) levels (5), an enzyme produced by the columnar epithelium of prostatic tissue in physiological conditions (6) which is found in the systemic circulation and used as biomarker to diagnose and follow up PC patients (7). However, about 10-20% of PC patients relapse on ADT and eventually progress to metastatic castration resistant prostate cancer  (mCRPC) (8). The androgen receptor (AR) and MYC proto-oncogene, bHLH transcription factor (cMYC) are commonly overexpressed in CRPC (9). Super-anti androgens, systemic chemotherapy, immunotherapy, and localized radiotherapy are typical treatment regimes in this setting (10) but they are nevertheless ineffective in the long term, and CRPC remains an incurable disease.

Very recently, therapy based on inhibition of Poly (ADP-ribose) polymerase inhibitors (PARP) have been approved by the American Food and Drug Administration (FDA) for treatment of mCRPC patients with defect of in the DNA repair genes (11). PARP inhibitors (PARPi) target DNA damage response (DDR), where they inhibit DNA repair pathway (12). Therefore, in DDR proficient tumors, combination of radiation with PARPi or other agents inhibiting the DDR might be an attractive therapeutic strategy. Furthermore, in primary hormone-na?ve newly diagnosed oligometastatic PC, radiotherapy to the prostate has been reported to be beneficial due to abscopal effects of radiation (13).

Epigenetic drugs such as those targeting bromodomain containing proteins (BRDs) are in preclinical and clinical trials also for PC (14). These BRDs tend to be upregulated in PC where their expression correlates with prognosis (15). In previously studies it was shown other bromodomain and extrateminal (BET) proteins are androgen regulated in which they maintain open chromatin conformation allowing androgen receptor (AR) to bind to key gene regulatory regions (15).

Aim of Study

This thesis will study the effects of the PARPi (Olaparib) and epigenetics inhibitor as readiosensiting agents.

Several cell lines models developed in house will be screened with in vitro clonogenic assay to determine the ability of cells to grow into colonies. An IncuCyte proliferation assay will be used to analyze confluence of cells over time.

Fluorescence-activated cell sorting (FACS) will be used to examine the cell cycle distribution upon the above-mentioned treatments, whereas western blot and qPCR will be used to assess the expression of the protein and genes regulating the cell cycle.

Furthermore, RNA-sequencing (RNA-seq) will be used to investigate gene expression levels upon exposure to different treatments with inhibitors.

Ethical and legal issues related to the thesis      

This research will not employ animals nor patient's material. Some of the inhibitors used in this study are subjected to MTA and NDA and results derived from the use of those are restricted from publication otherwise negotiated with Dr Urbanucci.

Financing

This project is financed by Dr Urbanucci¡¯s grant (the Norwegian Cancer Society grant # 198016-2018).

References

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