title: Targeted inhibition of ATR or CHEK1 reverses radioresistance in oral squamous cell carcinoma cells with distal chromosome arm 11q loss.
abstract: Oral squamous cell carcinoma (OSCC), a subset of head and neck squamous cell carcinoma (HNSCC), is the eighth most common cancer in the U.S.. Amplification of chromosomal band 11q13 and its association with poor prognosis has been well established in OSCC. The first step in the breakage-fusion-bridge (BFB) cycle leading to 11q13 amplification involves breakage and loss of distal 11q. Distal 11q loss marked by copy number loss of the ATM gene is observed in 25% of all Cancer Genome Atlas (TCGA) tumors, including 48% of HNSCC. We showed previously that copy number loss of distal 11q is associated with decreased sensitivity (increased resistance) to ionizing radiation (IR) in OSCC cell lines. We hypothesized that this radioresistance phenotype associated with ATM copy number loss results from upregulation of the compensatory ATR-CHEK1 pathway, and that knocking down the ATR-CHEK1 pathway increases the sensitivity to IR of OSCC cells with distal 11q loss. Clonogenic survival assays confirmed the association between reduced sensitivity to IR in OSCC cell lines and distal 11q loss. Gene and protein expression studies revealed upregulation of the ATR-CHEK1 pathway and flow cytometry showed G2 M checkpoint arrest after IR treatment of cell lines with distal 11q loss. Targeted knockdown of the ATR-CHEK1 pathway using CHEK1 or ATR siRNA or a CHEK1 small molecule inhibitor (SMI, PF-00477736) resulted in increased sensitivity of the tumor cells to IR. Our results suggest that distal 11q loss is a useful biomarker in OSCC for radioresistance that can be reversed by ATR-CHEK1 pathway inhibition.
authors: Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA; University of Pittsburgh Cancer Institute, Pittsburgh, PA.
authors: Madhav
authors: M
authors: Sankunny
authors: Rahul A
authors: RA
authors: Parikh
authors: Dale W
authors: DW
authors: Lewis
authors: William E
authors: WE
authors: Gooding
authors: William S
authors: WS
authors: Saunders
authors: Susanne M
authors: SM
authors: Gollin
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000532:radiotherapy; D045744:Cell Line, Tumor / Q000528:radiation effects; D000071877:Checkpoint Kinase 1; D002872:Chromosome Deletion; D020090:Chromosome Segregation; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics*; D004249:DNA Damage; D055785:Gene Knockdown Techniques; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints; D009062:Mouth Neoplasms / Q000235:genetics* / Q000532:radiotherapy; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011836:Radiation Tolerance; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1