Yes--you read that right!
The journal Cancer Discovery reports in a publish ahead-of-print article (abstract)the discovery of mutations in the discoidin domain receptor 2 tyrosine kinase (DDR2) gene in a series of lung squamous cell carcinomas (SQC) that may identify a potential therapeutic target similar to those described for lung adenocarcinomas. Interestingly, DDR2 is a receptor kinase that normally binds collagen as its ligand and has been shown to promote cell migration, proliferation, and survival when activated by ligand binding and phosphorylation.
While subtypes of lung adenocarcinoma (ADC) have been increasingly better defined and characterized on multiple levels with respect to identifying therapeutic targets/responses, minimal progress has been made with squamous cell carcinoma.
The authors of this study used conventional Sanger sequencing of 201 genes, including the entire tyrosine kinome, in an initial set of 20 primary lung SQC and matched normal controls and identified 2 samples with DDR2 mutations; a secondary screen of 48 lung SQC samples identified as additional 4 DDR2 mutations. Following this, the authors sequenced DDR2 in a validation cohort of 222 primary lung SQC samples and identified 5 additional samples with mutations. Excluding samples from lung SQC cell lines, there was an overall frequency of 3.2% of DDR2 mutations in primary lung SQC samples--about the same frequency reported for ALK fusion mutations in lung ADC.
The authors analyzed the TKIs imatinib and dasatinib, previously reported to inhibit DDR2, to evaluate whether targeting DDR2 mutated in SQC might be a potential therapeutic strategy. Dasatinib showed particular efficacy in inhibiting proliferation and promoting cell death through apoptosis in SQC cell ines with DDR2 mutations. In addition, they report one of 7 subjects from an early-phase trial of dasatinib or combination dasatinib and erlotinib with advanced stage lung SQC cancer who exhibited significant shrinkage in tumor size while receiving the dasatinib/erlotinib combination. The authors were able to perform direct sequencing of DDR2 in a pretreatment tumor specimen from this individual and identified a novel DDR2 kinase mutation.
This is an intriguing paper that you might well keep in mind. Hopefully, this may stimulate other investigators to not only look for other potential genomic alterations that either drive SQC and/or represent targetable proteins but also go back and scrutinize histological and other clinicopathological characteristics of lung SQC that may have therapeutic or prognostic importance.