Search

Castration-resistant prostate cancer (CRPC) is the most aggressive, incurable form of prostate cancer. MDV3100 (enzalutamide), an antagonist of the androgen receptor (AR), was approved for clinical use in men with metastatic CRPC. Although this compound showed clinical efficacy, many initial responders later developed resistance. To uncover relevant resistant mechanisms, we developed a model of spontaneous resistance to MDV3100 in LNCaP prostate cancer cells. Detailed characterization revealed that emergence of an F876L mutation in AR correlated with blunted AR response to MDV3100 and sustained proliferation during treatment. Functional studies confirmed that ARF876L confers an antagonist-to-agonist switch that drives phenotypic resistance. Finally, treatment with distinct antiandrogens or cyclin-dependent kinase (CDK)4/6 inhibitors effectively antagonized ARF876L function. Together, these findings suggest that emergence of F876L may (i) serve as a novel biomarker for prediction of drug sensitivity, (ii) predict a “withdrawal” response to MDV3100, and (iii) be suitably targeted with other antiandrogens or CDK4/6 inhibitors. Significance: We uncovered an F876L agonist-switch mutation in AR that confers genetic and phenotypic resistance to the antiandrogen drug MDV3100. On the basis of this finding, we propose new therapeutic strategies to treat patients with prostate cancer presenting with this AR mutation. Cancer Discov; 3(9); 1030–43. ©2013 AACR. See related commentary by Nelson and Yegnasubramanian, p. 971 This article is highlighted in the In This Issue feature, p. 953

Mantle cell lymphoma (MCL) is an aggressive malignancy that is characterized by poor prognosis. Large-scale pharmacological profiling across more than 100 hematological cell line models identified a subset of MCL cell lines that are highly sensitive to the B cell receptor (BCR) signaling inhibitors ibrutinib and sotrastaurin. Sensitive MCL models exhibited chronic activation of the BCR-driven classical nuclear factor-κB (NF-κB) pathway, whereas insensitive cell lines displayed activation of the alternative NF-κB pathway. Transcriptome sequencing revealed genetic lesions in alternative NF-κB pathway signaling components in ibrutinib-insensitive cell lines, and sequencing of 165 samples from patients with MCL identified recurrent mutations in TRAF2 or BIRC3 in 15% of these individuals. Although they are associated with insensitivity to ibrutinib, lesions in the alternative NF-κB pathway conferred dependence on the protein kinase NIK (also called mitogen-activated protein 3 kinase 14 or MAP3K14) both in vitro and in vivo. Thus, NIK is a new therapeutic target for MCL treatment, particularly for lymphomas that are refractory to BCR pathway inhibitors. Our findings reveal a pattern of mutually exclusive activation of the BCR-NF-κB or NIK-NF-κB pathways in MCL and provide critical insights into patient stratification strategies for NF-κB pathway-targeted agents.

To identify novel tumor suppressor genes involved in ovarian carcinogenesis, we generated four down-regulated suppression subtraction cDNA libraries from two early-stage (stage I/II) and two late-stage (stage III) primary ovarian tumors, each subtracted against cDNAs derived from normal ovarian epithelial cell brushings. Approximately 600-700 distinct clones were sequenced from each library. Comparison of down-regulated clones obtained from early- and late-stage tumors revealed genes that were unique to each library which suggested tumor-specific differences. We found 45 down-regulated genes that were common in all four libraries. We also identified several genes, the role of which in tumor development has yet to be elucidated, in addition to several under expressed genes, the potential role of which in carcinogenesis has been described previously (Bagnoli et al., Oncogene, 19: 4754-4763, 2000; Yu et al., Proc. Natl. Acad. Sci. USA, 96: 214-219, 1999; Mok et al., Oncogene, 12: 1895-1901, 1996). The differential expression of a subset of these genes was confirmed by semiquantitative reverse transcription-PCR using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as control in a panel of 15 stage I and 15 stage III tumors of mixed histological subtypes. Chromosomal sorting of library sequences revealed that several of the genes mapped to known regions of deletion in ovarian cancer. Loss of heterozygosity (LOH) analysis revealed multiple genomic regions with a high frequency of loss in both early- and late-stage tumors. To determine whether loss of expression of some of the genes corresponds to loss of an allele by LOH, we used a microsatellite marker for one of the novel genes on 8q and have shown that loss of expression of this novel gene correlates with loss of an allele by LOH. In conclusion, our analysis has identified down-regulated genes, which map to known as well as novel regions of deletions and may represent potential candidate tumor suppressor genes involved in ovarian cancer.