BACKGROUND: Microsatellite instability high (MSI-H) of sporadic colorectal carcinomas (CRC) is usually associated with improved prognosis and a high density of tumor-infiltrating lymphocytes. However, African Americans with MSI-H have poor prognosis.

AIM: To evaluate whether or not expression of different immune and tumor markers individually or in combination in African American MSI-H CRC associate with the prognosis status.

METHODS: Tissues Microarray (TMA) were prepared by microdissection from FFPE (Formalin Fixed Paraffin Embedded) blocks of 15 MSI-H patients. Immune markers (CD8+, Granzymes, Perforins, CD4+, STAT1, IRF1 and IRF5) and PD-L1 status were analyzed by immunohistochemistry (IHC). Demography and clinical data including TNM, tumor grading (WHO standard), histological type of the tumor, date of diagnosis, date of the last follow-up examination, treatment, comorbidities, metastasis, recurrence, 5-year disease-free survival and death were collected. RESULTS: There were 4 patients with improved prognosis (27%) with relatively high CD4 density (2 with >50% and 2 with 11-50%) regardless of PD-L1 status (3+/1-), stage (II,III), and other immune markers (CD8, CD4, Granzymes, Perforins, IRF1, IRF5 and STAT1). One of the improved prognosis patients with KRAS mutation has elevated expression of all considered immune markers besides CD4. There were 9 patients (6 dead, 3 alive) with poor prognosis, with different immune and tumor markers level (3 were PD-L1+ and 5 have relatively high CD4 count; but with low level of STAT1. There were also 2 patients with expected improved prognosis based on their immune markers level (stage II), however, they died within the 5 year period post-diagnosis, due to their age (98 and 87 years old).

Conclusion: MSI-H Colorectal cancer from African American patients has poor prognosis which may correlate with the nature of tumor-associated immune response. Other factors such as MSH3 defects might cancel the positive prognosis of MSI-H status. Nonetheless, low STAT1 and low CD4 may be indicators of poorer prognosis.

Citation Format: Umamaheshwari Golconda, Lena Sokol, Babak Shokrani, Edward Lee, Donna Hansel, Oluwole Fadare, Sandip Patel, Mehdi Nouraie, Hooman Soleimani, Zaki Sharif, Ali Afsari, Fareed Daremipouran, Hassan Brim, Hassan Ashktorab. Does poor prognosis in African Americans with MSI-H colorectal cancer associate with altered immune markers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4578. doi:10.1158/1538-7445.AM2017-4578