Faculty Bibliography

BACKGROUND: Recurrent mutations in the Speckle-Type POZ Protein (SPOP) gene occur in up to 15% of prostate cancers. However, the frequency and features of cancers with these mutations across different populations is unknown. OBJECTIVE: To investigate SPOP mutations across diverse cohorts and validate a series of assays employing high-resolution melting (HRM) analysis and Sanger sequencing for mutational analysis of formalin-fixed paraffin-embedded material. DESIGN SETTING AND PARTICIPANTS: 720 prostate cancer samples from six international cohorts spanning Caucasian, African American, and Asian patients, including both prostate-specific antigen-screened and unscreened populations, were screened for their SPOP mutation status. Status of SPOP was correlated to molecular features (ERG rearrangement, PTEN deletion, and CHD1 deletion) as well as clinical and pathologic features. RESULTS AND LIMITATIONS: Overall frequency of SPOP mutations was 8.1% (4.6% to 14.4%), SPOP mutation was inversely associated with ERG rearrangement (P<.01), and SPOP mutant (SPOPmut) cancers had higher rates of CHD1 deletions (P<.01). There were no significant differences in biochemical recurrence in SPOPmut cancers. Limitations of this study include missing mutational data due to sample quality and lack of power to identify a difference in clinical outcomes. CONCLUSION: SPOP is mutated in 4.6% to 14.4% of patients with prostate cancer across different ethnic and demographic backgrounds. There was no significant association between SPOP mutations with ethnicity, clinical, or pathologic parameters. Mutual exclusivity of SPOP mutation with ERG rearrangement as well as a high association with CHD1 deletion reinforces SPOP mutation as defining a distinct molecular subclass of prostate cancer.

Glioblastoma is one of the most challenging forms of cancer to treat. Here we describe a computational platform that integrates the analysis of copy number variations and somatic mutations and unravels the landscape of in-frame gene fusions in glioblastoma. We found mutations with loss of heterozygosity in LZTR1, encoding an adaptor of CUL3-containing E3 ligase complexes. Mutations and deletions disrupt LZTR1 function, which restrains the self renewal and growth of glioma spheres that retain stem cell features. Loss-of-function mutations in CTNND2 target a neural-specific gene and are associated with the transformation of glioma cells along the very aggressive mesenchymal phenotype. We also report recurrent translocations that fuse the coding sequence of EGFR to several partners, with EGFR-SEPT14 being the most frequent functional gene fusion in human glioblastoma. EGFR-SEPT14 fusions activate STAT3 signaling and confer mitogen independence and sensitivity to EGFR inhibition. These results provide insights into the pathogenesis of glioblastoma and highlight new targets for therapeutic intervention.

Adenoid cystic carcinomas (ACCs) are among the most enigmatic of human malignancies. These aggressive salivary gland cancers frequently recur and metastasize despite definitive treatment, with no known effective chemotherapy regimen. Here we determined the ACC mutational landscape and report the exome or whole-genome sequences of 60 ACC tumor-normal pairs. These analyses identified a low exonic somatic mutation rate (0.31 non-silent events per megabase) and wide mutational diversity. Notably, we found mutations in genes encoding chromatin-state regulators, such as SMARCA2, CREBBP and KDM6A, suggesting that there is aberrant epigenetic regulation in ACC oncogenesis. Mutations in genes central to the DNA damage response and protein kinase A signaling also implicate these processes. We observed MYB-NFIB translocations and somatic mutations in MYB-associated genes, solidifying the role of these aberrations as critical events in ACC. Lastly, we identified recurrent mutations in the FGF-IGF-PI3K pathway (30% of tumors) that might represent new avenues for therapy. Collectively, our observations establish a molecular foundation for understanding and exploring new treatments for ACC.

BACKGROUND: Acute myeloid leukemia (AML) is a heterogeneous disease with respect to presentation and clinical outcome. The prognostic value of recently identified somatic mutations has not been systematically evaluated in a phase 3 trial of treatment for AML. METHODS: We performed a mutational analysis of 18 genes in 398 patients younger than 60 years of age who had AML and who were randomly assigned to receive induction therapy with high-dose or standard-dose daunorubicin. We validated our prognostic findings in an independent set of 104 patients. RESULTS: We identified at least one somatic alteration in 97.3% of the patients. We found that internal tandem duplication in FLT3 (FLT3-ITD), partial tandem duplication in MLL (MLL-PTD), and mutations in ASXL1 and PHF6 were associated with reduced overall survival (P=0.001 for FLT3-ITD, P=0.009 for MLL-PTD, P=0.05 for ASXL1, and P=0.006 for PHF6); CEBPA and IDH2 mutations were associated with improved overall survival (P=0.05 for CEBPA and P=0.01 for IDH2). The favorable effect of NPM1 mutations was restricted to patients with co-occurring NPM1 and IDH1 or IDH2 mutations. We identified genetic predictors of outcome that improved risk stratification among patients with AML, independently of age, white-cell count, induction dose, and post-remission therapy, and validated the significance of these predictors in an independent cohort. High-dose daunorubicin, as compared with standard-dose daunorubicin, improved the rate of survival among patients with DNMT3A or NPM1 mutations or MLL translocations (P=0.001) but not among patients with wild-type DNMT3A, NPM1, and MLL (P=0.67). CONCLUSIONS: We found that DNMT3A and NPM1 mutations and MLL translocations predicted an improved outcome with high-dose induction chemotherapy in patients with AML. These findings suggest that mutational profiling could potentially be used for risk stratification and to inform prognostic and therapeutic decisions regarding patients with AML. (Funded by the National Cancer Institute and others.).

Identifying the spectrum of genetic alterations that cooperate with critical oncogenes to promote transformation provides a foundation for understanding the diversity of clinical phenotypes observed in human cancers. Here, we performed integrated analyses to identify genomic alterations that co-occur with oncogenic BRAF in melanoma and abrogate cellular dependence upon this oncogene. We identified concurrent mutational inactivation of the PTEN and RB1 tumor suppressors as a mechanism for loss of BRAF/MEK dependence in melanomas harboring (V600E)BRAF mutations. RB1 alterations were mutually exclusive with loss of p16(INK4A), suggesting that whereas p16(INK4A) and RB1 may have overlapping roles in preventing tumor formation, tumors with loss of RB1 exhibit diminished dependence upon BRAF signaling for cell proliferation. These findings provide a genetic basis for the heterogeneity of clinical outcomes in patients treated with targeted inhibitors of the mitogen-activated protein kinase pathway. Our results also suggest a need for comprehensive screening for RB1 and PTEN inactivation in patients treated with RAF and MEK-selective inhibitors to determine whether these alterations are associated with diminished clinical benefit in patients whose cancers harbor mutant BRAF.