Calcitonin Gene-related Peptide Inhibits Tumor Cell Proliferation of Hepatocellular Carcinoma Cells Through the Ras/MEK/ERK Pathway

Abstract

Calcitonin gene-related peptide (CGRP) is widely distributed in the central and peripheral nervous systems and regulates physiological functions. Several neuropeptides are involved in the development and progression of hepatocellular carcinoma (HCC), although the role of CGRP in HCC pathogenesis is unclear. This study attempted to clarify the effects of CGRP on tumor progression in HCC cells. CGRP and its receptors, calcitonin receptor-like receptor and receptor activity-modifying protein-1, were expressed in HCC tissues and HCC cell lines. When Huh7 cells were cultured with CGRP 10 M for 24 h, cell proliferation was significantly inhibited. In addition, the total and phosphorylated protein levels of Ras and mitogen-activated protein kinase (MAPK) family proteins, MAP kinase (MEK) 1/2 and extracellular signal-regulated kinase (ERK) 1/2, were also inhibited by CGRP 10 −10 M incubation. CGRP significantly increased the protein levels of cAMP response element binding protein (CREB) and its phosphorylated form in the nuclei of Huh 7 cells. Furthermore, pretreatment of CGRP receptor antagonist CGRP 8-37 abolished the increases in CREB and pCREB protein levels in the nuclei of Huh7 cells. In addition, pretreatment of CGRP 8-37 and cAMP inhibitor Rp-cAMP tended to reverse the ERK inhibition in Huh 7 cells cultured with CGRP. These results suggest that CGRP inhibits HCC cell proliferation via CREB activation and Ras/MEK/ERK pathway. CGRP may play an important role in the amelioration of cancer progression.

Expression of the Calcitonin Receptor-like Receptor (CALCRL) in Normal and Neoplastic Tissues

“…CGRP has proangiogenic and prolymphangiogenic properties; thus, it can enhance tumour-associated angiogenesis and tumour growth [ 119 ]. CGRP expression has been detected in a high percentage of medullary thyroid carcinomas [ 120 , 121 ], in small-cell lung carcinomas and corresponding cell lines [ 122 , 123 ], and in hepatocellular carcinomas and corresponding cell lines [ 124 ]. Notably, CGRP can increase the invasive and migratory capacities of cultured prostate cancer cells by 30–40%, and there is some evidence that CGRP (via CGRPR) promotes prostate cancer metastasis to bone [ 106 ].…”

“…In contrast to adrenomedullin (and CGRP), minimal information is available concerning the expression patterns of CALCRL and the various RAMP isoforms in human tumours. Expression patterns have been reported for human glioblastomas and glioblastoma cell lines (CALCRL, RAMP1/2/3) [ 125 , 126 , 127 ], gastric cancer (CALCRL, RAMP1/2/3) [ 128 ], colorectal cancer (CALCRL, RAMP2/3) [ 91 ], pancreatic cancer (CALCRL, RAMP1/2/3) [ 93 , 94 ], hepatocellular carcinomas and corresponding cell lines (CALCRL, RAMP1/2/3) [ 98 , 124 ], renal cancer (CALCRL, RAMP2/3) [ 100 ], pheochromocytomas (CALCRL, RAMP2) [ 129 ], prostate cancer and corresponding cell lines (CALCRL, RAMP2/3) [ 103 , 104 ], breast cancer and corresponding cell lines (CALCRL, RAMP2/3) [ 109 ], and ovarian cancer (CALCRL) [ 111 ]. However, most studies thus far have been limited to analyses of mRNA.…”