Revisited analysis of a SHIVA01 trial cohort using functional mutational analyses successfully predicted treatment outcome

It still remains to be demonstrated that using molecular profiling to guide therapy improves patient outcome in oncology. Classification of somatic variants is not straightforward, rendering treatment decisions based on variants with unknown significance (VUS) hard to implement. The oncogenic activity of VUS and mutations identified in 12 patients treated with molecularly targeted agents (MTAs) in the frame of SHIVA01 trial was assessed using Functional Annotation for Cancer Treatment (FACT). MTA response prediction was measured in vitro, blinded to the actual clinical trial results, and survival predictions according to FACT were correlated with the actual PFS of SHIVA01 patients. Patients with positive prediction had a median PFS of 5.8 months versus 1.7 months in patients with negative prediction (P < 0.05). Our results highlight the role of the functional interpretation of molecular profiles to predict MTA response

Altered adenosine-to-inosine RNA editing in human cancer

Adenosine-to-inosine (A-to-I) RNA editing was recently shown to be abundant in the human transcriptome, affecting thousands of genes. Employing a bioinformatic approach, we identified significant global hypoediting of Alu repetitive elements in brain, prostate, lung, kidney, and testis tumors. Experimental validation confirmed this finding, showing significantly reduced editing in Alu sequences within MED13 transcripts in brain tissues. Looking at editing of specific recoding and noncoding sites, including in cancer-related genes, a more complex picture emerged, with a gene-specific editing pattern in tumors vs. normal tissues. Additionally, we found reduced RNA levels of all three editing mediating enzymes, ADAR, ADARB1, and ADARB2, in brain tumors. The reduction of ADARB2 correlated with the grade of malignancy of glioblastoma multiforme, the most aggressive of brain tumors, displaying a 99% decrease in ADARB2 RNA levels. Consistently, overexpression of ADAR and ADARB1 in the U87 glioblastoma multiforme cell line resulted in decreased proliferation rate, suggesting that reduced A-to-I editing in brain tumors is involved in the pathogenesis of cancer. Altered epigenetic control was recently shown to play a central role in oncogenesis. We suggest that A-to-I RNA editing may serve as an additional epigenetic mechanism relevant to cancer development and progression

Therapeutic implications of activating noncanonical PIK3CA mutations in head and neck squamous cell carcinoma

Alpelisib selectively inhibits the p110α catalytic subunit of PI3Kα and is approved for treatment of breast cancers harboring canonical PIK3CA mutations. In head and neck squamous cell carcinoma (HNSCC), 63% of PIK3CA mutations occur at canonical hotspots. The oncogenic role of the remaining 37% of PIK3CA noncanonical mutations is incompletely understood. We report a patient with HNSCC with a noncanonical PIK3CA mutation (Q75E) who exhibited a durable (12 months) response to alpelisib in a phase II clinical trial. Characterization of all 32 noncanonical PIK3CA mutations found in HNSCC using several functional and phenotypic assays revealed that the majority (69%) were activating, including Q75E. The oncogenic impact of these mutations was validated in 4 cellular models, demonstrating that their activity was lineage independent. Further, alpelisib exhibited antitumor effects in a xenograft derived from a patient with HNSCC containing an activating noncanonical PIK3CA mutation. Structural analyses revealed plausible mechanisms for the functional phenotypes of the majority of the noncanonical PIK3CA mutations. Collectively, these findings highlight the importance of characterizing the function of noncanonical PIK3CA mutations and suggest that patients with HNSCC whose tumors harbor activating noncanonical PIK3CA mutations may benefit from treatment with PI3Kα inhibitors

Therapeutic implications of activating noncanonical PIK3CA mutations in head and neck squamous cell carcinoma.

Alpelisib selectively inhibits the p110α catalytic subunit of PI3Kα and is approved for treatment of breast cancers harboring canonical PIK3CA mutations. In head and neck squamous cell carcinoma (HNSCC), 63% of PIK3CA mutations occur at canonical hotspots. The oncogenic role of the remaining 37% of PIK3CA noncanonical mutations is incompletely understood. We report a patient with HNSCC with a noncanonical PIK3CA mutation (Q75E) who exhibited a durable (12 months) response to alpelisib in a phase II clinical trial. Characterization of all 32 noncanonical PIK3CA mutations found in HNSCC using several functional and phenotypic assays revealed that the majority (69%) were activating, including Q75E. The oncogenic impact of these mutations was validated in 4 cellular models, demonstrating that their activity was lineage independent. Further, alpelisib exhibited antitumor effects in a xenograft derived from a patient with HNSCC containing an activating noncanonical PIK3CA mutation. Structural analyses revealed plausible mechanisms for the functional phenotypes of the majority of the noncanonical PIK3CA mutations. Collectively, these findings highlight the importance of characterizing the function of noncanonical PIK3CA mutations and suggest that patients with HNSCC whose tumors harbor activating noncanonical PIK3CA mutations may benefit from treatment with PI3Kα inhibitors

Comparing genomic landscape of early stage, treatment naïve and late stage, drug resistant EGFR-mutant lung adenocarcinomas

While, the genomic landscape of early stage, treatment naïve lung adenocarcinomas (LUADs) has been described quite elaborately in recent literature, the genomic profile of late stage, drug resistant tumors remains largely unknown. Further, most of the published studies are based on smoker dominated Caucasian cohorts and EGFR-mutant LUAD remains under-represented in them. Despite response rates of upto 70% to EGFR tyrosine kinase inhibitors (TKIs), resistance ensues in most of these EGFR-mutant patients, limiting responses to a median of 10-12 months. Thus, to better understand the evolution of these tumors in context of drug resistance, we perform a comparative analysis of the mutational and copy number landscape of early stage, treatment naïve vs late stage, resistant tumors. Whole exome sequencing was performed on: (i) 100 tumor sectors from 24 early stage, treatment naïve EGFR-mutant LUAD cases. (ii)  81 biopsies from 58 late stage, TKI and chemotherapy resistant cases. Copy number analysis using SNP arrays was performed for a subset of these patients. The significantly higher mutation burden in the late stage, drug resistant tumors elucidated a driver mutation landscape beyond just recurrent TP53 mutations, which was dominated by PIK3CA (14%), RB1 (10%), NF1 (7%) and other rare mutations in EGFR (in 5/58 cases), many of which co-occurred with the T790M mutation. Functional studies validated the oncogenicity of some of these rare mutations in the PI3K/AKT1 pathway. The copy number landscape revealed pervasive, truncal genome doubling events in both cohorts (~80% cases). While comparable fraction of genome was affected by overall copy number gains or losses (copy change &gt;=1) across the two cohorts (49.2% vs 46.3%, P=0.51), significantly higher fraction of genome was affected by amplifications (copy change &gt;=2; 8.7% vs 5%, P=0.02) and loss of heterozygosity (LOH; 33.1% vs 20.6%, P=0.003) in the drug resistant tumors compared to the treatment naive tumors. In summary, our study reveals (i) increased mutation and driver burden with co-occurring resistance mutations and (ii) higher fraction of genome with amplifications and LOH in the drug resistant cohort, suggesting ways in which genomic landscape of EGFR-mutant LUAD evolves, potentially making them more tolerant to drug treatment