Combination Therapy Could Lead to Reduction in Prostate Cancer Recurrence

“Prostate cancer patients who receive radiotherapy could soon be treated more effectively, according to research published today in the British Journal of Cancer. Although radiotherapy is an effective treatment for the disease, about a third of patients go on to experience a recurrence of their cancer. Scientists funded by Yorkshire Cancer Research at the University of York have identified a population of radiation resistant prostate cancer cells, and by combining low doses of a common cancer drug with radiotherapy treatment they have increased the sensitivity of these cells to radiation. The findings could lead to a reduction in recurrences.”

HDAC Inhibitor Confers Radiosensitivity to Prostate Stem-Like Cells

“Background: Radiotherapy can be an effective treatment for prostate cancer, but radiorecurrent tumours do develop. Considering prostate cancer heterogeneity, we hypothesised that primitive stem-like cells may constitute the radiation-resistant fraction. Methods: Primary cultures were derived from patients undergoing resection for prostate cancer or benign prostatic hyperplasia. After short-term culture, three populations of cells were sorted, reflecting the prostate epithelial hierarchy, namely stem-like cells (SCs, α2β1integrinhi/CD133+), transit-amplifying (TA, α2β1integrinhi/CD133−) and committed basal (CB, α2β1integrinlo) cells. Radiosensitivity was measured by colony-forming efficiency (CFE) and DNA damage by comet assay and DNA damage foci quantification. Immunofluorescence and flow cytometry were used to measure heterochromatin. The HDAC (histone deacetylase) inhibitor Trichostatin A was used as a radiosensitiser. Results: Stem-like cells had increased CFE post irradiation compared with the more differentiated cells (TA and CB). The SC population sustained fewer lethal double-strand breaks than either TA or CB cells, which correlated with SCs being less proliferative and having increased levels of heterochromatin. Finally, treatment with an HDAC inhibitor sensitised the SCs to radiation. Interpretation: Prostate SCs are more radioresistant than more differentiated cell populations. We suggest that the primitive cells survive radiation therapy and that pre-treatment with HDAC inhibitors may sensitise this resistant fraction.”


Androgen Receptor Signaling Fuels DNA Repair and Radioresistance in Prostate Cancer

“Successful treatment by genotoxic modalities including radiotherapy is commonly hampered by treatment resistance in advanced cancers. Two new studies now reveal that androgen receptor signaling transcriptionally upregulates a large subset of DNA repair genes, thereby enhancing the repair capacity and promoting radioresistance of prostate cancer. These results provide a mechanistic rationale for a combined treatment by ionizing radiation and androgen deprivation therapy.”

Androgen Receptor Signaling Regulates DNA Repair in Prostate Cancers

“We demonstrate that the androgen receptor (AR) regulates a transcriptional program of DNA repair genes that promotes prostate cancer radioresistance, providing a potential mechanism by which androgen deprivation therapy (ADT) synergizes with ionizing radiation (IR). Using a model of castration-resistant prostate cancer, we show that second-generation antiandrogen therapy results in downregulation of DNA repair genes. Next, we demonstrate that primary prostate cancers display a significant spectrum of AR transcriptional output which correlates with expression of a set of DNA repair genes. Employing RNA-seq and ChIP-seq, we define which of these DNA repair genes are both induced by androgen and represent direct AR targets. We establish that prostate cancer cells treated with IR plus androgen demonstrate enhanced DNA repair and decreased DNA damage and furthermore that antiandrogen treatment causes increased DNA damage and decreased clonogenic survival. Finally, we demonstrate that antiandrogen treatment results in decreased classical non-homologous end joining.”