BACKGROUND Prostate cancer is a heterogeneous disease, but current treatments are not based on molecular stratification. We hypothesized that metastatic, castration-resistant prostate cancers with DNA-repair defects would respond to poly(adenosine diphosphate [ADP]–ribose) polymerase (PARP) inhibition with olaparib. METHODS We conducted a phase 2 trial in which patients with metastatic, castration-resistant prostate cancer were treated with olaparib tablets at a dose of 400 mg twice a day. The primary end point was the response rate, defined either as an objective response according to Response Evaluation Criteria in Solid Tumors, version 1.1, or as a reduction of at least 50% in the prostate-specific antigen level or a confirmed reduction in the circulating tumor-cell count from 5 or more cells per 7.5 ml of blood to less than 5 cells per 7.5 ml. Targeted next-generation sequencing, exome and transcriptome analysis, and digital polymerase-chain-reaction testing were performed on samples from mandated tumor biopsies. RESULTS Overall, 50 patients were enrolled; all had received prior treatment with docetaxel, 49 (98%) had received abiraterone or enzalutamide, and 29 (58%) had received cabazitaxel. Sixteen of 49 patients who could be evaluated had a response (33%; 95% confidence interval, 20 to 48), with 12 patients receiving the study treatment for more than 6 months. Next-generation sequencing identified homozygous deletions, deleterious mutations, or both in DNA-repair genes — including BRCA1/2, ATM, Fanconi’s anemia genes, and CHEK2 — in 16 of 49 patients who could be evaluated (33%). Of these 16 patients, 14 (88%) had a response to olaparib, including all 7 patients with BRCA2 loss (4 with biallelic somatic loss, and 3 with germline mutations) and 4 of 5 with ATM aberrations. The specificity of the biomarker suite was 94%. Anemia (in 10 of the 50 patients [20%]) and fatigue (in 6 [12%]) were the most common grade 3 or 4 adverse events, findings that are consistent with previous studies of olaparib. CONCLUSIONS Treatment with the PARP inhibitor olaparib in patients whose prostate cancers were no longer responding to standard treatments and who had defects in DNA-repair genes led to a high response rate.

It is widely held that cells with metastatic properties such as invasiveness and expression of matrix metalloproteinases arise through the stepwise accumulation of genetic lesions arising from genetic instability and "clonal evolution." By contrast, we show here that in melanomas invasiveness can be regulated epigenetically by the microphthalmia-associated transcription factor, Mitf, via regulation of the DIAPH1 gene encoding the diaphanous-related formin Dia1 that promotes actin polymerization and coordinates the actin cytoskeleton and microtubule networks at the cell periphery. Low Mitf levels lead to down-regulation of Dia1, reorganization of the actin cytoskeleton, and increased ROCK-dependent invasiveness, whereas increased Mitf expression leads to decreased invasiveness. Significantly the regulation of Dia1 by Mitf also controls p27 The ability of cancer cells to acquire properties of invasiveness and the potential to metastasize is not entirely understood. In the traditional model, genetic instability within a tumor would lead within some cells to the accumulation of genetic and stable epigenetic lesions that are compatible with increased invasiveness and metastatic potential. These genetic lesions and stable epigenetic modifications, such as histone and DNA methylation, would be inherited by the metastatic progeny and dictate alterations in gene expression compatible with metastatic potential (for a review, see Baylin and Ohm 2006). Alternatively, invasive potential could represent a specific epigenetic state that is inherently unstable and nonheritable, being imposed by the microenvironment of the cell; in this model, properties associated with metastasis may be lost once the invasive cell has taken up residence in another location. While considerable resources have been expended on trying to pinpoint genetic mutations that correlate with metastatic potential and, more recently, the resulting stable epigenetic changes, the molecular mechanisms that would underpin a dynamic epigenetic model for cancer metastasis have been relatively little explored.Some cancer types, such as melanoma, are intrinsically more metastatic than others, and it has been postulated that the ability of melanomas to invade and proliferate may be related to the inherent ability of melanoblasts to migrate from the neural crest and proliferate to populate the epidermis and hair follicles Gupta et al. 2005). Some genes have been identified whose expression appears to correlate with the ability of melanomas to metastasize. The expression of SLUG, for example, can promote metastasis and facilitates the loss of E-cadherin (Gupta et al. 2005), a key molecule that mediates melanocyte adhesion to keratinocytes that is lost when melanomas acquire invasive potential (Haass et al. 2005), while NEDD9, an adaptor protein that interacts with focal adhesion kinase, is frequently overexpressed in metastatic melanoma and promotes invasiveness (Kim et al. 2006). However, despite these advances, and some preliminary investigations into the concept tha...

AR gene aberrations are rare in prostate cancer prior to primary hormone treatment but emerge with castration resistance. To determine AR gene status using a minimally-invasive assay that could have broad clinical utility, we developed a targeted next-generation sequencing approach amenable to plasma DNA that covers all the AR coding bases and regions of the genome highly informative in prostate cancer. We here sequenced 274 plasma samples from 97 castration-resistant prostate cancer patients treated with abiraterone at two institutions. After controlling for the fraction of normal DNA in patients’ circulation, we quantified AR copy number state and point mutations. AR aberrations by the two mechanisms were inversely correlated, supported further by the enrichment of non-synonymous versus synonymous mutations in AR copy number normal as opposed to AR gain samples. While AR copy number was unchanged from pre-treatment to progression and no mutant AR alleles showed signal for acquired gain, we observed emergence of T878A or L702H AR amino acid changes in 13% at progression on abiraterone. Patients with AR gain or T878A or L702H pre-abiraterone (45%) were 4.9 times and 7.8 times less likely to have a decline in PSA by ≥50% or ≥90% respectively and had a significantly worse overall (HR 7.33, 95% CI 3.51-15.34) and progression-free (HR 3.73, 95% CI 2.17-6.41) survival. Evaluation of plasma AR using next-generation sequencing could identify cancers with primary resistance to abiraterone.

It is unclear whether a single clone metastasizes and remains dominant over the course of lethal prostate cancer. We describe the clonal architectural heterogeneity at different stages of disease progression by sequencing serial plasma and tumor samples from 16 ERG-positive patients. By characterizing the clonality of commonly occurring deletions at 21q22, 8p21, and 10q23, we identified multiple independent clones in metastatic disease that are differentially represented in tissue and circulation. To exemplify the clinical utility of our studies, we then showed a temporal association between clinical progression and emergence of androgen receptor (AR) mutations activated by glucocorticoids in about 20% of patients progressing on abiraterone and prednisolone or dexamethasone. Resistant clones showed a complex dynamic with temporal and spatial heterogeneity, suggesting distinct mechanisms of resistance at different sites that emerged and regressed depending on treatment selection pressure. This introduces a management paradigm requiring sequential monitoring of advanced prostate cancer patients with plasma and tumor biopsies to ensure early discontinuation of agents when they become potential disease drivers.

The controls that enable melanoblasts and melanoma cells to proliferate are likely to be related, but so far no key regulator of cell cycle progression specific to the melanocyte lineage has been identified. The microphthalmia-associated transcription factor Mitf has a crucial but poorly defined role in melanoblast and melanocyte survival and in differentiation. Here we show that Mitf can act as a novel anti-proliferative transcription factor able to induce a G1 cell-cycle arrest that is dependent on Mitf-mediated activation of the p21(Cip1) (CDKN1A) cyclin-dependent kinase inhibitor gene. Moreover, cooperation between Mitf and the retinoblastoma protein Rb1 potentiates the ability of Mitf to activate transcription. The results indicate that Mitf-mediated activation of p21Cip1 expression and consequent hypophosphorylation of Rb1 will contribute to cell cycle exit and activation of the differentiation programme. The mutation of genes associated with melanoma, such as INK4a or BRAF that would affect either Mitf cooperation with Rb1 or Mitf stability respectively, would impair Mitf-mediated cell cycle control.