Mining The Circulating Immune Cell Transcriptome For Ovarian Cancer-Specific Biomarkers: A Proof Of Concept Study

The continuous interplay between cancer cells and immune system leads to significant changes in the function of innate as well as adaptive immune cells. These changes occur through direct contact between the immune cells and the cancer cells as well as through soluble factors released from the tumor microenvironment. Since the immune cells are considered as “first responders” to a site of infection or to aberrant cells and pre-cancerous lesions, it is likely that immune cell function is influenced even at an early stage of tumor development. We have therefore hypothesized that changes in the proteome and transcriptome of circulating immune cells (conveniently obtained via venipuncture) should be studied closely to identify disease-specific biomarkers. Here, we present data from a proof-of-concept study that shows specific differences in the expression of a panel of genes in the immune cell transcriptome in peripheral blood mononuclear cells (PBMCs) obtained from healthy donors and patients with ovarian cancer. In our initial study, we isolated RNA from PBMCs of four healthy women and 5 ovarian cancer patients. Using an Illumina microarray we established that over 122 genes were up-regulated and 64 genes were downregulated in the PBMCs isolated from cancer patients. Gene cluster analysis showed that based on expression, the healthy donor samples clustered separately than the samples from ovarian cancer patients. For the purpose of additional exploration and to also identify genes (microRNA, etc, for example) that are typically not represented in conventional microarrays, we also conducted RNASeq experiments. Bioinformatics analysis showed that in PBMCs from ovarian cancer patients, 507 and 717 genes were upregulated or downregulated, respectively. The RNASeq data strongly validated the results from the microarray analysis. Additional validation on PBMC samples obtained from postmenopausal healthy women and ovarian cancer patients (n=20/cohort) using quantitative PCR is currently underway in our laboratories. Furthermore, we are also employing a murine ovarian cancer model to identify changes in the gene expression patterns in immune cells in tumor bearing versus non-tumor bearing immunecompetent mice. The results from these studies are leading to identification of candidate gene sets that can be used as potential biomarkers form ovarian cancer. These transcript-based biomarkers represent several important immunologic pathways- T cell receptor, cytokine activation and others. Studies are also continuing to determine if these biomarkers are expressed in all or only a subset of the immune cells isolated from ovarian cancer patients. Citation Format: Shitanshu Uppal, Arvinder Kapur, Erin Medlin, Mildred Felder, Hadi Shojaie, Nicole Gregorich, Manish S. Patankar, Jesus Gonzalez-Bosquet. Mining the circulating immune cell transcriptome for ovarian cancer-specific biomarkers: a proof of concept study [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS11.