Carlos E. Zuazo

BRAF inhibitors have a 50–70% response rate in melanoma but are less effective for thyroid cancer. Differential response may be from activation or expression of downstream mitogen-activated protein kinase (MAPK) pathway genes. Retrospective analysis compared whole exome and transcriptome sequencing in melanoma and thyroid cancers from April 2019 to October 2023. The MAPK Activation Score (MPAS) was calculated using Z-score normalized/log-transformed values indicating expression across 10 MAPK-associated genes. Our tumor registry provided outcome data. BRAF V600E mutations were identified in 33 of 200 (17%) melanomas and 14 (7%) had other BRAF mutations (V600K/R). Of 49 thyroid tumor samples, BRAF V600E mutations were found in 19 (39%). RNA expression of BRAF and the 10 MAPK-associated genes were increased in melanomas with V600E compared to wild-type BRAF (p = 0.02). Conversely, BRAF V600E mutation in thyroid cancer was not associated with increased expression nor MAPK pathway activation. No significant difference in overall survival based on BRAF mutation was observed in the subset of patients where data was available. The MAPK pathway is differentially affected by the different cancers, with increased MAPK activation observed in melanoma and not in thyroid cancer. This may account in part for the observed differential response to BRAF inhibitors.

Background: Gene fusions occur when two independent genes form a hybrid gene through genomic rearrangements, which often leads to abnormal expression and function of an encoded protein. In hematological and solid cancers, oncogenic fusions may be prognostic, diagnostic, or therapeutic biomarkers. Improved detection and understanding of the functional implications of such fusions may be beneficial for patient care. Methods: We performed a retrospective analysis of our internal genomic database to identify known and novel gene fusions in different solid tumors seen in our community cancer center. We then investigated the clinical implications of the fusions we identified. Results: We identified 420 known oncogenic fusions and 25 unclassified gene fusions across twenty-six different cancer types. Of 420 fusion-positive tumors with known fusions, there were 366 unique gene fusions. Conclusions: About 10% of tumors investigated had oncogenic fusions, which supports the notion that comprehensive molecular profiling, including RNA sequencing, should be provided for patients with advanced cancers.