5’-UTR mutation in OXA1L drives cSCC metastasis via tumor dedifferentiation and immune evasion

Summary: Abstract Body: The pathogenic role of non-coding mutations in skin cancers is not fully defined. To identify driver mutations in non-coding untranslated regions (UTR), we analyzed 41 metastatic and 57 primary cutaneous squamous cell carcinomas (cSCC). OXA1L, a gene essential for mitochondrial translation, contained the highest incidence of 5’-UTR mutations. We observed more frequent mutations in the 5’-UTR of OXA1L in metastatic cSCC (9/41; 22%) compared to primary tumors (2/57; 3.5%); this 6.3-fold enrichment is higher than that of known metastatic cSCC driver mutations. Functionally, the 5’-UTR mutation in OXA1L was associated with its lower expression in cSCC patients, and primary keratinocytes edited to harbor mutant OXA1L demonstrated decreased OXA1L mRNA stability. OXA1L-mutant cells exhibited accelerated neoplastic invasion in human skin organoid and tumor spheroid models compared to isogenic cells with wild-type OXA1L. Strikingly, tail vein injection in mice with IGR1, a cell line-containing mutant OXA1L, enhanced tumor cell seeding in the lung and spleen compared to CRISPR-corrected IGR1 with wild-type OXA1L. Examination of isogenic tumor spheroids revealed enhanced dedifferentiation and immune evasion in OXA1L-mutant spheroids. Consistent with this, we observed higher T-cell exhaustion in OXA1L-mutant metastatic cSCC patients. As OXA1L maintains mitochondrial function, OXA1L-mutant cells showed altered metabolomics, leading to fructose-1,6-bisphosphate accumulation that reduced aldolase activity and enhanced glutathione activity. Our findings identify a driver recurrent 5’-UTR point mutation in metastatic cSCC and underscore its pathogenic role in promoting cancer hallmarks. Ankit Srivastava¹, Isoline Donohue¹, Angela M. Peralta¹, Audrey Nguyen¹, Aiko Tan¹, Jasmine Garcia¹, Tiffany Jiang¹, Dane Sessions¹, Lek-Wei Seow¹, Tomas Bencomo¹, Jiangbin Ye², Bruce Ashford³, Marie Ranson³, David Kashatus⁴, Carolyn Lee^{1, 5} 1. Dermatology, Stanford University, Stanford, CA, United States. 2. Stanford University School of Medicine, Stanford, CA, United States. 3. University of Wollongong Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia. 4. University of Virginia, Charlottesville, VA, United States. 5. VA Palo Alto Healthcare System, Palo Alto, CA, United States. UV Biology/Injury and Non-melanoma Cancers