RAC1 genomic aberrations as predictive biomarkers for Head and Neck Squamous Cell Carcinoma (HNSCC)
Refereed conference paper presented and published in conference proceedings

Times Cited
Web of Science1WOS source URL (as at 20/10/2020) Click here for the latest count
Altmetrics Information

Other information
AbstractRAC1 is a small GTPase with known oncogenicity. Mutations of RAC1 are highly relevant to melanoma. Yet, little is known about RAC1 aberrations in other human cancers, including HNSCC. Pan-cancer analysis of 32 cancer types from the TCGA reveals that RAC1 mutations only affect 12/32 cancer types and HNSCC is the 2nd most frequently affected (2.64%; 14/510 cases), after melanoma (4.59%, 22/479 cases). 28/34 cancer types harbor RAC1 copy number alterations, including HNSCC (2.08% cases, all are amplifications). Among all 14 HNSCC-associated RAC1 mutations found in the TCGA cohort, RAC1 p.A159V mutation (residing in the highly conserved G5 Box of RAC1) appears to be particularly prevalent in HNSCC (6/14 cases), suggesting a likely mutant-specific role in HNSCC. HNSCC patients with somatic RAC1 aberrations [gene amplification/copy number gain/hotspot mutations (p.P29, p.K116 and p.A159)] have poorer overall survival (OS)(P=4.555e-5; median survival of 30.91 months vs 68.43 months) and disease-free survival (DFS) (P=5.49e-5; 27.89 months vs unreached median) vs. RAC1-unaltered HNSCC patients. RAC1-mutated tumors are also associated with a higher rate of TP53 mutation (P=2.07e-6), and a lower rate of HPV infection (P=7.397e-6; 7.7% vs. 87.2%; Fisher’s Exact test). Further, RAC1-altered patients are of more advanced T clinical staging (T3/4 vs T1/2; P=0.0312) and with more gross/microscopic extension (P=0.0111; 59/119 vs 54/201). These evidences strongly suggest that HNSCC with RAC1 aberrations are more aggressive and may serve as a prognostic biomarker for HNSCC. To further elucidate the biological function of RAC1 mutations in HNSCC, we analyzed the mutational profile of RAC1-mutated HNSCC tumors which showed enriched mutations of 3 tumor suppressor genes: FAT1, FAT4 and CSMD3 (P=0.0001, P=0.0038 and P=0.0467 respectively). Gene set enrichment analysis (GSEA) of RAC1-mutated HNSCC also demonstrates significant dysregulation of immune-related gene sets (vs. RAC1-WT tumors) including increased interleukin-6 (IL-6) production (P<0.0001), a pro-tumorigenic inflammatory cytokine known to be involved in HNSCC tumorigenesis and progression. A previous study showed that overexpression of RAC1 activating mutation (p.V12) could upregulate IL-6 production in a cervical cancer model, HeLa, which is supportive of a RAC1/IL-6 axis in HNSCC. This is further supported by our RNAseq finding that RAC1-mutated HNSCC tumors do have significant upregulation of MYD88 (P=0.0436), a gene that has been shown to induce IL-6 secretion in HNSCC cells. Subsequent Tumor Immune Estimation Resource (TIMER) analysis shows that RAC1-mutated HNSCC primary tumors have higher infiltrating neutrophil levels than RAC1-WT tumors (P=0.019). Our findings may uncover a novel tumorigenic mechanism by RAC1 mutations in HNSCC, first linking IL-6 dysregulation to an oncogene mutation in HNSCC.
All Author(s) ListHoi Lam NGAN, Yuchen LIU, Peony Hiu Yan POON, Vivian Wai Yan LUI
Name of ConferenceAnnual Meeting of the American-Association-for-Cancer-Research (AACR)
Start Date of Conference29/03/2019
End Date of Conference03/04/2019
Place of ConferenceAtlanta
Country/Region of ConferenceUnited States of America
Proceedings TitleCancer Research
Volume Number79
Issue NumberSuppl 13
LanguagesEnglish-United States

Last updated on 2020-21-10 at 02:42