Abstract LB019: DUSP4 overexpression exerts anti-tumor effects in vivo in pancreatic cancer xenografts in nu/nu mice
Authors: Singh Chandra K. , Ndiaye Mary A. , Chhabra Gagan , Nihal Minakshi , Ahmad Nihal 
Published: April 2023

Abstract
Pancreatic cancer (PC) remains one of the most lethal of all human malignancies, being highly aggressive and difficult to treat if diagnosed at late stages. Therefore, it is important to dissect molecular mechanisms implicated in PC pathophysiology. Dual specificity phosphatase-4 (DUSP4) is a phosphatase known to negatively regulate the mitogen-activated protein (MAP) kinase family (MAPK/ERK, SAPK/JNK, P38), which are involved in multiple cancers, including PC. Previously, using tissue microarray containing a variety of pancreatic cancers and normal pancreatic tissues, we found that DUSP4 was significantly downregulated in human PC. We also demonstrated that forced overexpression of DUSP4 resulted in anti-proliferative responses in MIA PaCa-2 human PC cells (Cancer Res 2016; 76 (14_Supplement): 3667). Here, we expanded our study to determine, i) the effects of DUSP4 overexpression on tumorigenicity in vivo, and ii) the molecular mechanisms associated with DUSP4 overexpression-mediated anti-proliferative responses. MIA PaCa-2 cells were stably transfected with DUSP4 overexpression (OE) plasmid or its empty vector (pCMV6) control, followed by subcutaneous implantation into nu/nu mice (n=8 each group). Tumor growth was measured weekly for 6 weeks followed by excision of tumors and molecular analyses. We found significant reduction in tumor volume and weight in DUSP4 OE group. Further, we found marked reduction in p-ERK1/2 and p-P38 proteins in tumors from DUSP4 OE group. To determine the global mechanisms of DUSP4, we analyzed DUSP4-overexpressing MIA PaCa-2 cell lysates using quantitative global proteomics. Overall, 1678 proteins were identified with ≥2 unique peptides. Out of these, 54 proteins were significantly modulated ≥1.6-fold. Using Ingenuity Pathway Analysis (IPA), we found the association of modulated proteins with increased apoptosis and inhibited invasive and malignant tumors. The top five modulated proteins identified in response to DUSP4 OE were ADD3, PDLIM1, COL2A1, SLC20A1 and CALB2, with the first three being upregulated and the remaining two downregulated. Based on published studies in other cancers, these data support the tumor suppressor role of DUSP4 in PC since i) the loss of ADD3 and PDLIM1 (both cytoskeleton-related proteins) have been found to promote tumor growth, ii) higher expression of COL2A1 has been associated with delayed tumor recurrence, iii) higher expression of SLC20A1 (sodium-phosphate symporter) and CALB2 (calcium-binding protein) are known to be associated with cancer progression. The specific roles of these proteins in PC are not well known, providing us novel opportunities for future investigations. Overall, our data support the tumor suppressor role of DUSP4 in PC and warrants further research to validate our findings.
Citation Format: Chandra K. Singh, Mary A. Ndiaye, Gagan Chhabra, Minakshi Nihal, Nihal Ahmad. DUSP4 overexpression exerts anti-tumor effects in vivo in pancreatic cancer xenografts in nu/nu mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB019.