Abstract 4375: ALPPL2 is involved in MAPK signal pathway of pancreatic cancer
Authors: Gong Ke Wei , Hamid Bilal , Castro Kenny W. , McDermott Martina S. , Epstein Forrest , Chau Kevin , Hu Chuhong , Zhang Jun , Lu Ming , Hoffstrom Benjamin G. , O'Brien Neil A. , Slamon Dennis J. 
Published: March 2024

Abstract
Background: Alkaline phosphatase placental-like 2 (ALPPL2) is a member of the alkaline phosphatase family. ALPPL2 is currently being investigated as a novel therapeutic target due to its cancer-specific expression. However, our knowledge of ALPPL2 biological function in cancer is limited. Here we describe an interaction between ALPPL2 and MAPK signaling pathway in pancreatic cancer.
Materials and Methods: ALPPL2 mRNA expression in a panel of 27 pancreatic cell lines was determined by RNAseq. Protein expression and phosphorylation were measured by Western blot. ALPPL2 or ALPP were overexpressed in pancreas cell lines through a Lentiviral packaging system. MEK inhibitor (trametinib) activity was assessed in the same panel of cell lines using a 6-day cell proliferation assay on a Synentec Cellavista imaging system. MEK inhibitor resistant cell lines were developed by culturing cells in increasing concentrations of MEK162.
Results: We hypothesized that pancreatic cancer cells with high ALPPL2 expression may be less sensitive to MEK inhibition. Our study from a panel of 27 pancreatic cancer cell lines showed that there was no correlation between ALPPL2 expression and response to trametinib. Western blot showed that the level of phospho-ERK was reduced in PANC1 and HPAC cells at 6 hours after trametinib treatment. Signaling rebounded at 24 and 48 hours, though it remained below baseline. Surprisingly, ALPPL2 expression increased at 24 and 48 hours after trametinib treatment, however, the mRNA of ALPPL2 and ALPP was down-regulated in three pancreatic cancer cell lines conditioned to be MEK inhibitor resistant. To understand the role of ALPPL2 in the MAPK signaling pathway in response to MEK inhibition, ALPPL2 and ALPP were overexpressed in 2 pancreatic cancer cell lines: YAPC and PSN-1 whose ALPPL2 and ALPP were undetected by Western blot prior to transfection. Overexpression of ALPPL2 or ALPP in YAPC cells resulted in more ERK phosphorylation with no change in total ERK, it also resulted in increased total and phospho-S6, and decreased phospho-STAT3 with no change in total STAT3. The amount of total and phospho-ERK were not changed in PSN-1 with overexpression of ALPPL2 or ALPP, however, it did result in increased total and phospho-S6, decreased phospho-STAT3. Interestingly, the expression of ALPPL2 and ALPP in YAPC cells with ALPPL2 or ALPP overexpression was increased at 48 hours after trametinib treatment.
Discussion: To our knowledge, this is the first study to report that ALPPL2 interacts with the MAPK signaling pathway in pancreatic cancer cells. The activated MAPK signaling pathway appears to control ALPPL2 expression. The MAPK signaling pathway may regulate ALPPL2 expression through transcription and protein metabolism. We have also shown that ALPPL2 expression can activate MAPK signaling pathway. Our findings that ALPPL2 expression can be increased after trametinib treatment provide further rationale for targeting ALPPL2 in cancer.
Citation Format: Ke Wei Gong, Bilal Hamid, Kenny W. Castro, Martina S. McDermott, Forrest Epstein, Kevin Chau, Chuhong Hu, Jun Zhang, Ming Lu, Benjamin G. Hoffstrom, Neil A. O'Brien, Dennis J. Slamon. ALPPL2 is involved in MAPK signal pathway of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4375.