Abstract 4575: mRNA expression in paired saliva and blood samples from different cancer indices

Abstract Introduction: Liquid biopsies have become gradually accepted, as a non-invasive alternative to traditional tumor biopsies in the field of oncology. The FDA and other regulatory bodies have already approved blood-based tests and researchers are working on validating urine, saliva and buccal swabs as alternative sample sources. This study’s main goal was to compare mRNA expression levels, in matched blood and saliva samples from cancer patients, as well as apparently healthy individuals. Methods: We collected matched saliva and blood samples from 35 individuals, including 27 patients diagnosed with cancers including Breast (4), Lung (4), Colon (5), Melanoma (3), Pancreatic (4), Prostate (7) cancer along with 9 healthy participants. The samples were collected in Wren’s proprietary buffer kit and RNA was extracted via TRIzol-based method. RNA sequencing was carried out on an Illumina Novaseq 6000. The data was analyzed using high performance computing (HPC) through PartekFlow software with the BWA aligner (hg38). Results: Nearly 94% of the genes found in saliva and 60% of the genes in blood were matched across all cancer types, with the exception of pancreatic cancer in blood, which showed only about 30% matching. We further evaluated both groups based on housekeeping genes (1003 genes) and the known cancer-associated genes as listed in the OncoKB database (1154 genes) for each cancer type. In addition, we investigated the expressions of 412 and 241 cancer genes priorly validated and used in IVD assays, respectively, in our lab. We found that 78-80% of the genes in blood were common across all cancer types, while saliva samples showed 64-73% commonality. Only 43% of genes detected in saliva from pancreatic cancer matched other cancer types. Out of the 241 internally validated cancer genes 68-71% genes were detected in blood and 57-65% in saliva in this cohort except pancreatic cancer where only 30% was detected. Out of the 412 genes, we found 67-69% in blood and 51-58% in saliva, again with the exception of pancreatic cancer, exhibits only 26% of genes. Additionally, 98% of housekeeping genes from blood and 71-87% of housekeeping genes from saliva were consistent, except for pancreatic cancer, which showed only 35%. Conclusion: Our study indicates that the majority of mRNA (94%) detected in saliva from various cancer types was also detected in blood, compared to healthy controls. This suggests that exploring mRNA-based biomarkers development in saliva could be even a more convenient alternative to blood. Citation Format: Srinivas V. Koduru, Mark Kidd, Abdel Halim. mRNA expression in paired saliva and blood samples from different cancer indices [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4575.