Abstract P044: A genetically engineered mouse Sertoli cell line survives chronic humoral immune factors when grafted into diabetic mice
Authors: Washburn Rachel L. , Hibler Taylor , Dufour Jannette M. 
Published: January 2023

Patients with uncontrolled diabetes have an increased risk of developing cancer, therefore controlling their blood glucose and insulin levels is imperative. An effective treatment to accomplish this is transplantation of insulin-producing pancreatic islets. However, these patients must take chronic immunosuppressants to prevent graft rejection, which also increases cancer risk. An alternative to traditional transplantation is to transduce immunoregulatory cells such as Sertoli cells (SC), which survive as grafts without immune suppressants, to express insulin. We have previously transduced a mouse SC tumor line (MSC-1) to express human insulin (MSC1-HI), demonstrated that they survive (at 70-75%) when grafted into diabetic mice after 50 days, and confirmed their sustained expression of human insulin. Since complement is an important part of immune rejection, we hypothesize that one mechanism SC use to survive is inhibition of complement by expression of complement inhibitory proteins (CIP). We confirmed that primary mouse SC (pSC), MSC-1 cells, and MSC1-HI cells survive human complement activation in vitro while controls are killed, indicating that SC must be inhibiting complement, and microarray analyses of pSC and MSC-1 cells identified gene expression of 14 different CIP. We immunostained MSC-1 and MSC1-HI grafts to study deposition of C9, the lytic pore component of the complement membrane attack complex. In MSC1-HI grafts, C9 increased from about 10 positive cells/mm2 graft to roughly 40 positive cells/mm2 graft, and a dramatic increase in C9 deposition was observed on MSC-1 grafts—from about 4 positive cells/mm2 to well over 350 positive cells/mm2. Furthermore, we found that MSC1-HI grafts were significantly larger at day 50 than MSC-1 grafts. The MSC1-HI grafts also increased in size by almost 300% between days 20 and 50 post-transplantation as compared to MSC-1 grafts, which decreased in size by 64%. Thus, it appears that MSC-1 grafts are still rejecting while MSC1-HI grafts are growing, indicating some level of tumorigenesis. Indeed, insulin has been shown to be a growth factor for SC, hence we propose that increased expression of insulin in the MSC-1 cancer cell line is encouraging tumorigenesis in diabetic mice. Taken together, these data indicate that MSC1-HI cells undergo tumorigenesis and can survive and proliferate in spite of complement activation, which may be playing a role in MSC-1 graft reduction. Since complement can be a powerful anti-tumor and transplant rejection mechanism, understanding how these SC tumor cells evade complement killing has significance in both treating cancer and increasing grafted organ survival. As diabetes patients are more susceptible to tumors, further studying the relationship between insulin and tumorigenesis will increase knowledge to allow for more effective management of tumors.

Citation Format: Rachel L. Washburn, Taylor Hibler, Jannette M. Dufour. A genetically engineered mouse Sertoli cell line survives chronic humoral immune factors when grafted into diabetic mice. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P044.