Abstract 1725: Mutationally activated KRAS(G12D) upregulates the expression of axonal guidance cue Semaphorin-5A in pancreatic cancer
Authors: Saxena Sugandha , Tomar Babita , Wu Lingyun , Awaji Mohammad , Rachagani Satyanarayan , Ouellette Michel J. , Batra Surinder K. , Dave Bhavana J. , Singh Rakesh K. 
Published: August 2019

Abstract
Mutation of KRAS is commonly found in different human cancers and is generally responsible for driving tumorigenesis. Unfortunately, direct inhibitors of KRAS are not available. Thus, scientists are in search of alternative strategies that can repress the oncogenic properties of KRAS and can benefit a large number of cancer patients. Drugs targeting KRAS downstream effectors are under investigation but are facing numerous challenges in their clinical implementation. Accumulating evidence suggests that the genetic status of KRAS can modulate the role of axonal guidance cue family members in tumorigenesis. Previous reports from our laboratory have identified upregulation of one such molecule Semaphorin-5A (SEMA5A) in murine model based on KRAS gene mutation in pancreatic progenitor cells that bear a striking similarity to the human PDAC condition. We utilized PDX-cre-LSL-Kras(G12D) (KC) for studying Sema5A expression and observed no expression of Sema5A in the normal pancreas, derived from the control PDX-cre mice, however, we observed Sema5A expression in PDX-cre-LSL-Kras(G12D) mice beginning at ten weeks of age. Furthermore, we observed an increase in SEMA5A expression in the tumors of mice aged at twenty-five and fifty weeks, representing a fully developed PDAC condition. To investigate the relationship between KRAS status and SEMA5A, we assessed whether KRAS(G12D) alters the expression of SEMA5A using immortalized human pancreatic ductal cells having endogenous wild-type KRAS but an exogenous expression of KRAS(G12D) [HPNE-KRAS]. We detected higher expression of SEMA5A in the KRAS(G12D) bearing HPNE-KRAS cells in comparison with their control counterpart HPNE-Tert. Stable clones of CD18/HPAF cell line knocked-down for KRAS(G12D) demonstrated inhibition of SEMA5A expression in comparison with their respective Control CD18/HPAF cells bearing an endogenous expression of mutant KRAS. We also analyzed SEMA5A expression in the cells lines derived from the serial passage of COLO 357 cells through mice to achieve highly invasive/metastatic variants also leading to the selection of cells that express mutationally activated KRAS. L3.3 cells, with no point mutations in the KRAS gene, expressed lower SEMA5A in comparison with highly metastatic L3.6pl cells bearing a point mutation in codon 12, thereby encoding a mutationally activated KRAS(G12D). Together, our data suggest that KRAS(G12D) mutation directly upregulates the expression of axon guidance cue molecule-SEMA5A in the PDAC cells. Our findings open an avenue of molecules that can serve as secondary targets to repress KRAS activity in pancreatic cancer.
Citation Format: Sugandha Saxena, Babita Tomar, Lingyun Wu, Mohammad Awaji, Satyanarayan Rachagani, Michel J. Ouellette, Surinder K. Batra, Bhavana J. Dave, Rakesh K. Singh. Mutationally activated KRAS(G12D) upregulates the expression of axonal guidance cue Semaphorin-5A in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1725.