TPH1 and 5-HT7 Receptor Overexpression Leading to Gemcitabine-Resistance Requires Non-Canonical Permissive Action of EZH2 in Pancreatic Ductal Adenocarcinoma

Abstract

In the present study, we investigated the regulatory mechanisms underlying overexpression of EZH2, tryptophan hydroxylase 1 (TPH1), and 5-HT7, in relation to gemcitabine resistance and CSC survival in PDAC cells. In aggressive PANC-1 and MIA PaCa-2 cells, knock-down (KD) of EZH2, TPH1, or HTR7 induced a decrease in CSCs and recovery from gemcitabine resistance, while preconditioning of less aggressive Capan-1 cells with 5-HT induced gemcitabine resistance with increased expression of EZH2, TPH1, and 5-HT7. Such effects of the gene KD and 5-HT treatment were mediated through PI3K/Akt and JAK2/STAT3 signaling pathways. EZH2 KD or GSK-126 (an EZH2 inhibitor) inhibited activities of these signaling pathways which altered nuclear level of NF-kB, Sp1, and p-STAT3, accompanied by downregulation of TPH1 and 5-HT7. Co-immunoprecipation with EZH2 and pan-methyl lysine antibodies revealed that auto-methylated EZH2 served as a scaffold for binding with methylated NF-kB and Sp1 as well as unmethylated p-STAT3. Furthermore, the inhibitor of EZH2, TPH1, or 5-HT7 effectively regressed pancreatic tumor growth in a xenografted mouse tumor model. Overall, the results revealed that long-term exposure to 5-HT upregulated EZH2, and the noncanonical action of EZH2 allowed the expression of TPH1-5-HT7 axis leading to gemcitabine resistance and CSC population in PDAC.

Inhibition of serotonin biosynthesis in neuroendocrine neoplasm suppresses tumor growthin vivo

“…Similarly, Tph1 inhibition combined with gemcitabine further decreased tumor growth relative to gemcitabine alone in PDAC xenograft tumors (Chaudhary et al, 2021). Those results support an ongoing clinical trial in PDAC (NCT03910387) to determine the effect of telotristat ethyl at promoting weight stability in patients treated with gemcitabine and paclitaxel.…”

“…Recent studies have revealed important functions of serotonin regulation in tumorigenesis and drug resistance in in PDAC (Chaudhary et al, 2021, Jiang et al, 2017, colon cancer (Liu et al, 2021, Schneider et al, 2021, breast cancer (Gautam et al, 2016), and others. In our analysis of Tph1 expression in small cell lung carcinoma cells, high Tph1 was detected in the doxorubicin resistant H69AR cell line as compared to the parental H69 cell line which is sensitive to doxorubicin (Figure 2C).…”

siRNA treatment targeting integrin α11 overexpressed via EZH2- driven axis inhibits drug-resistant breast cancer progression

“…EZH2 normally is not expressed in healthy adult tissues but is only found in actively dividing cells, such as during fetal development [52]. In contrast to the action of EZH2 in developing embryonic cells, where it exerts transcriptional repression of genes involved in cell differentiation [53][54][55][56], overexpressed EZH2 in cancer cells induces growth-related gene expression in a PRC2-independent manner [55,57].…”

Serotonin signalling in cancer: Emerging mechanisms and therapeutic opportunities

“… 50 It also implicates in maintenance of cancer stem cells (CSCs) populations and gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC) through 5‐HTR7‐PI3K/AKT and 5‐HTR7/JAK2/STAT3 pathways. 72 The downregulation of diverse 5‐HTRs in pancreatic cancer cells was revealed to suppress tumour proliferation and migration. 73 , 74 , 75 In the case of PCa, 5‐HT generated by neuroendocrine (NE) cells exerted a pro‐proliferative effect on PCa cells via HTR1A‐MAPK/ERK and HTR1A‐PI3K/AKT signalling pathways and suppressed apoptosis via the HTR1B‐PI3K/AKT axis.…”

“…5‐HT was reported to amplify Warburg effect of pancreatic cancer cells through the PI3K/mTOR axis mediated by HTR2B‐LYN‐p85 complex 50 . It also implicates in maintenance of cancer stem cells (CSCs) populations and gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC) through 5‐HTR7‐PI3K/AKT and 5‐HTR7/JAK2/STAT3 pathways 72 . The downregulation of diverse 5‐HTRs in pancreatic cancer cells was revealed to suppress tumour proliferation and migration 73–75 .…”