Mutations of the LIM protein AJUBA mediate sensitivity of head and neck squamous cell carcinoma to treatment with cell-cycle inhibitors

Abstract

The genomic alterations identified in head and neck squamous cell carcinoma (HNSCC) tumors have not resulted in any changes in clinical care, making the development of biomarker-driven targeted therapy for HNSCC a major translational gap in knowledge. To fill this gap, we used 59 molecularly characterized HNSCC cell lines and found that mutations of AJUBA,SMAD4 and RAS predicted sensitivity and resistance to treatment with inhibitors of polo-like kinase 1 (PLK1), checkpoint kinases 1 and 2, and WEE1. Inhibition or knockdown of PLK1 led to cell-cycle arrest at the G2/M transition and apoptosis in sensitive cell lines and decreased tumor growth in an orthotopic AJUBA-mutant HNSCC mouse model. AJUBA protein expression was undetectable in most AJUBA-mutant HNSCC cell lines, and total PLK1 and Bora protein expression were decreased. Exogenous expression of wild-type AJUBA in an AJUBA-mutant cell line partially rescued the phenotype of PLK1 inhibitor-induced apoptosis and decreased PLK1 substrate inhibition, suggesting a threshold effect in which higher drug doses are required to affect PLK1 substrate inhibition. PLK1 inhibition was an effective therapy for HNSCC in vitro and in vivo. However, biomarkers to guide such therapy are lacking. We identified AJUBA, SMAD4 and RAS mutations as potential candidate biomarkers of response of HNSCC to treatment with these mitotic inhibitors.

PDK1 Mediates NOTCH1-Mutated Head and Neck Squamous Carcinoma Vulnerability to Therapeutic PI3K/mTOR Inhibition

“…We obtained and subjected 50 human papilloma virus (HPV)-negative and 9 HPV-positive HNSCC cell lines to whole-exome sequencing, reverse-phase protein array analysis, and gene expression profiling as described previously (14,16,17). All the cell lines were genotyped by short tandem repeat analysis, and all cell lines were mycoplasma-free at the time of testing with a Mycoplasma Detection Kit (Lonza).…”

“…Cell lines were classified as sensitive based on IC 70 values less than the peak plasma concentration for each drug. To determine if crosscomparison of the PI3K/mTOR inhibitors as a class was feasible, we compared their drug sensitivity patterns with those of three cell-cycle kinase inhibitors we tested previously (17). The PI3K/ mTOR pathway inhibitors clustered separately from the cell-cycle inhibitors ( Supplementary Fig.…”

“…We then compared drug sensitivity to common driver genes identified in HNSCC tumors from The Cancer Genome Atlas (TCGA; ref. 17). Our cell lines did not have any mutations in 11 of the top 50 mutated genes, and six genes were mutated in only one cell line, precluding comparison.…”

A gene signature associated with prognosis and immune processes in head and neck squamous cell carcinoma

“…NSD1 mutation, in combination with the K36 M substitution, could converge on altering methylation of histone H3 at K36 (H3K36), subsequently blocking cellular differentiation and promoting oncogenesis . AJUBA mutation was identified as a possible candidate biomarker for HNSCC responsiveness to treatment with mitotic inhibitors . NFE2L2 and CUL3 (NFE2L2 protein complex partner) mutation suggested that the NFE2L2 oxidative stress pathway was more active in the high SIG12 group than in the low.…”

Novel DNA targeted therapies for head and neck cancers: clinical potential and biomarkers

“…Another study suggested WEE1 inhibition gene signature as pharmacodynamic biomarker based on mRNA expression in tissue biopsies [ 101 ]. According to a very recent study focused on the use of mitotic inhibitors in HNSCC, mutations in AJUBA, SMAD4 and RAS predict the sensitivity to CHK1 and WEE1 inhibitors [ 102 ]. However, these suggested biomarkers are not validated yet, nor implemented in clinical trials.…”