Abstract 5525: Profiling counter-regulatory and cytotoxic immune pathways with cellular biomarkers in thyroid cancer patients

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Clinical studies suggested an association between thyroid cancer outcome and patient immunologic function. Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) and Programmed Death 1 (PD-1) are strong negative regulators of immune function whose aberrant function has been associated with poor outcomes in patients with solid malignancies. We carried out this study to compare the degree and patterns of expression of CTLA4 and PD-1 in peripheral circulating mononuclear cells in adult patients with thyroid cancer (N=21) compared with adult healthy controls (N=5). We used multiparameter flow cytometry to determine the absolute cell count per ml of blood for the cells of interest. Functional assays of immunologic competence of B-cell, T-cell as well as NK cell subpopulations was assessed by granzyme-B and interferon (IFN) gamma production following PMA/ionomycin stimulation in vitro using standard assay method. Differences in specific cell count between patients and healthy control was assessed by F-test statistics and p-value <0.05 was considered significant. There was no significant difference between cancer patients and healthy controls in the overall numbers of T-cell, B-cell, and NK cell subsets. Similarly, the proportion of CD4, CD8 and NK cell subsets with CTLA4, PD-1, IFN-gamma or Granzyme-B expression with and without PMA/ionomycin stimulation were not significantly different when comparing patients with thyroid cancer to healthy controls. Within the thyroid cancer patient population, however, the distribution of CD4 (+) T-cells, total B-cells, plasma cells, and PD ligand 1-expressing monocytes, macrophages and dendritic cells i.e. CD64 (+) PD-L1 (+) was significantly different between patient with active disease and those in remission. The Granzyme-B (+) CD4 (+) T-cell was significantly lower in patients in remission than in patients with active disease both with and without in vitro activation with PMA/ionomycin (0.08 vs. 0.19 per ml blood × 10⁁6; p=0.03). Intriguingly, functional profiling in a limited number of thyroid cancer patients revealed a markedly impaired ability of CD8 (+) T-cells to produce IFN-gamma and Granzyme B following PMA/ionomycin stimulation. Thus suggesting possible immune exhaustion in this subpopulation of thyroid cancer patients. Overall, our results show a trend toward impaired cytotoxic immune pathway in thyroid cancer patients with active disease burden when compared to patients in remission. A similar trend was observed in comparison to healthy subjects but the small number of control subjects limits statistical significance. Further elucidation of this finding using larger patient sample is clearly warranted and currently ongoing. (Supported by Career Development Award (NCI P50 CA128613) to TK Owonikoko and the Georgia Cancer Coalition Distinguished Scholar Award to DM Shin, SS Ramalingam, FR Khuri, and TK Owonikoko) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5525. doi:10.1158/1538-7445.AM2011-5525