Finally: An Active Prostate Cancer Drug That Doesn’t Target Androgen

Most of the recent developments in prostate cancer treatment have addressed the timing and duration of androgen deprivation, who should receive radiation treatments, and the timing of the few available chemotherapy options. But this month’s big news is a welcome change: metastatic castration-resistant prostate cancers (mCRPCs) that harbor mutations in BRCA2 or one of a few other genes have a remarkable response to olaparib (Lynparza), a drug that inhibits the enzyme PARP1. Continue reading…

Study Finds Gene Mutations Sensitize Tumors to Specific Cancer Drugs

“Mutations in ARID1a, which are common in many cancer types, disrupt DNA damage repair in cancer cells, allowing the cancer to progress. This gene may also be an Achilles’ heel when treating certain tumors, according to a team of researchers at The University of Texas MD Anderson Cancer Center.

“The study, published in Cancer Discovery, discovered that certain mutations in ARID1a (AT-rich interactive domain-containing protein 1a), a gene recently implicated in cancer progression, sensitize some tumors to PARP inhibitor drugs, such as olaparib, veliparib and BMN673, which block DNA damage repair pathways.

” ‘Our results showed, particularly in the ARID1a deficient cells, PARP inhibitors are more effective than in other cancer cells,’ says Guang Peng, M.D., Ph.D, assistant professor, Clinical Cancer Prevention, and senior author of the study. ‘Based on the mechanism we’ve discovered, we propose a new approach for targeting these mutant cancer cells.’ ”

Chemotherapy Timing is Key to Success — Nanoparticles that Stagger Delivery of 2 Drugs Knock out Aggressive Tumors in Mice

“MIT researchers have devised a novel cancer treatment that destroys tumor cells by first disarming their defenses, then hitting them with a lethal dose of DNA damage.

“In studies with mice, the research team showed that this one-two punch, which relies on a nanoparticle that carries two drugs and releases them at different times, dramatically shrinks lung and breast tumors. The MIT team, led by Michael Yaffe, the David H. Koch Professor in Science, and Paula Hammond, the David H. Koch Professor in Engineering, describe the findings in the online edition of Science Signaling.”

Editor’s note: This story is about a new treatment that has been studied in mice. While it is possible that the treatment could eventually make it to clinical trials with humans, the treatment currently cannot be used to treat cancer.

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.”


Phosphoproteomic Characterization of DNA Damage Response in Melanoma Cells Following MEK/PI3K Dual Inhibition

“Growing evidence suggests that successful intervention in many human cancers will require combinations of therapeutic agents. Critical to this effort will be a detailed understanding of the crosstalk between signaling networks that modulate proliferation, cell death, drug sensitivity, and acquired resistance. Here we investigated DNA-damage signaling elicited by small-molecule inhibitors against MAP/ERK kinase (MEK) and PI3K in melanoma cells. This work, performed using cutting-edge mass spectrometry proteomics, uncovered a burst of signaling among proteins in the DNA-damage pathway upon initiation of the cell-death program by agents targeting the RAS–RAF–MEK and PI3K–AKT–mTOR pathways. These signals may prove important to the short- and long-term sensitivity of tumor cells to MEK- and PI3K-targeted therapies.”

Scientists Discover Why Combo Treatment Works for People with High-Risk Prostate Cancer

The vast majority of high-risk prostate cancer cases are caused by abnormally high activity of a protein called the androgen receptor. Present in many prostate cells, androgen receptors detect androgen hormones (including testosterone), and in response, turn on or off genes. Genes that are regulated by androgen hormones are critical for the development of the prostate and maintenance of its function. But when the androgen receptor is overly active, which can occur via several different processes in the aging prostate, it can activate genes that can lead to uncontrolled proliferation of prostate cells. This contributes to the development of aggressive prostate cancer. Continue reading…

New Prospects for Small Cell Lung Cancer Patients (Part I)

Small cell lung carcinoma (SCLC) accounts for about 15% of lung cancers, but it is the deadliest form of lung malignancy. Only 6% of patients with SCLC survive beyond 5 years after diagnosis. In the last few years, new therapies—targeted therapies in particular—have been developed and approved by the U.S. Food and Drug Administration (FDA) for treating other, more common forms of lung cancer such as adenocarcinoma. However, not much progress has been made in addressing SCLC, which is usually treated with a combination of fairly toxic chemotherapeutics and radiotherapy. Many patients respond to these harsh treatments (ie, their tumors shrink), but only transiently. The disease recurs within a few months to 1 year and, at that point, is no longer treatable. Continue reading…

Unstable Chromosomes Linked to Less Favorable Response to Radiation Therapy and Surgery in Prostate Cancer Patients

“Detailed evaluation of a prostate cancer tumor biopsy may predict treatment outcomes for image-guided radiation therapy (IGRT) or surgery for prostate cancer, according to research presented today at the American Society for Radiation Oncology’s (ASTRO’s) 55th Annual Meeting. The study results indicate that patients who have abnormal levels of breaks at common fragile sites (CFSs), sites within the chromosomes that are sensitive to DNA damage, are more likely to have their cancer to return—treatment failure. These CFSs break abnormalities are usually associated with instability of the cell’s DNA, a phenomenon that is particularly associated with cancer.”

A Hormone-DNA Repair Circuit Governs the Response to Genotoxic Insult

“Alterations in DNA repair promote tumor development, but the impact on tumor progression is poorly understood. Here, discovery of a biochemical circuit linking hormone signaling to DNA repair and therapeutic resistance is reported. Findings demonstrate that androgen receptor (AR) activity is induced by DNA damage, and promotes expression and activation of a gene expression program governing DNA repair. Subsequent investigation revealed that activated AR promotes resolution of double-strand breaks and resistance to DNA damage both in vitro and in vivo. Mechanistically, DNAPKcs was identified as a key target of AR after damage, controlling AR-mediated DNA repair and cell survival after genotoxic insult. Finally, DNAPKcs was shown to potentiate AR function, consistent with a dual role in both DNA repair and transcriptional regulation. Combined, these studies identify the AR-DNAPKcs circuit as a major effector of DNA repair and therapeutic resistance, and establish a new node for therapeutic intervention in advanced disease.”