SAN DIEGO – Cutaneous squamous cell carcinomas from organ transplant recipients had a more aggressive molecular profile than did tumor samples from immunocompetent patients, according to an RNA sequencing study presented at the annual meeting of the American Society for Dermatologic Surgery.
Specimens from organ transplant recipients showed greater induction of biologic pathways related to cancer signaling, fibrosis, and extracellular matrix remodeling, said Dr. Cameron Chesnut, a dermatologist in private practice in Spokane, Wash., who carried out the research while he was a dermatologic surgery resident at the University of California, Los Angeles.
Furthermore, the TP53 tumor suppressor gene was inhibited at least five times more in samples from organ transplant recipients, compared with those from immunocompetent patients, Dr. Chesnut said in an interview.
Squamous cell carcinoma (SCC) is the most common cancer to occur after organ transplantation, Dr. Chesnut and his associates noted. The malignancy is 65-250 times more common, is more than 4 times more likely to metastasize, and has a mortality rate of 5% compared with a rate of less than 1% in immunocompetent patients, based on data published online in the journal F1000 Prime Reports, they said.
To characterize these high-risk SCCs and compare them with lower-risk SCCs, the researchers performed RNA sequencing of three normal skin samples and SCC specimens from 15 patients – 7 organ transplant recipients and 8 otherwise healthy individuals. The researchers used an Illumina GAIIx RNA Seq instrument to generate RNA sequencing libraries of the specimens. They also used the web-based Ingenuity Pathway Analysis technique to identify the major biological pathways regulated within the tumors.
In all, 690 highly expressed genes were induced at least fivefold in SCCs from organ transplant recipients compared with those from otherwise healthy patients. These genes encoded pathways related to fibrosis, extracellular remodeling, the cell cycle, and tumor signaling, the investigators said. The COX-2 pathway for prostaglandin synthesis also was induced fivefold or more in the high-risk SCCs compared with those from immunocompetent patients, Dr. Chesnut added.
The researchers also identified 1,290 highly expressed genes that were inhibited at least fivefold in SCCs from organ transplant recipients compared with specimens from immunocompetent patients. The most strongly inhibited pathways were related to sterol biosynthesis and epithelial differentiation, followed by nucleotide excision repair, interleukin-6 and IL-17, and apoptosis, they said.
Based on these findings, novel therapeutics might someday be able to target specific biologic pathways that are highly induced in SCCs from organ transplant recipients, Dr. Chesnut said. “It’s hard to say what the most likely candidates are,” but based on the study findings, “regulating inflammation may be a target,” he added. Dr. Chesnut and his associates reported no external funding sources or conflicts of interest.