Parathyroid Hormone-related Protein Regulates Tumor-relevant Genes in Breast Cancer Cells

Abstract

The effect of endogenous parathyroid hormone-related protein (PTHrP) on gene expression in breast cancer cells was studied. We suppressed PTHrP expression in MDA-MB-231 cells by RNA interference and analyzed changes in gene expression by microarray analysis. More than 200 genes showed altered expression in response to a PTHrP-specific small interfering (si) RNA (siPTHrP). Cell cycle-regulating gene CDC2 and genes (CDC25B and Tome-1) that control CDC2 activity showed increased expression in the presence of siPTHrP. CDC2 activity was also found to be higher in siPTHrP-treated cells. Studies with PTHrP peptides 1-34 and 67-86, forskolin, and a PTH1 receptor (PTH1R)-specific siRNA showed that PTHrP regulates CDC2 and CDC25B, at least in part, via PTH1R in a cAMP-independent manner. Other siPTHrP-responsive genes included integrin ␣6 (ITGA6), KISS-1, and PAI-1. When combined, siRNAs against ITGA6, PAI-1, and KISS-1 could mimic the negative effect of siPTHrP on migration, whereas siKISS-1 and siPTHrP similarly reduced the proliferative activity of the cells. Comparative expression analyses with 50 primary breast carcinomas revealed that the RNA level of ITGA6 correlates with that of PTHrP, and higher CDC2 and CDC25B values are found at low PTHrP expression. Our data suggest that PTHrP has a profound effect on gene expression in breast cancer cells and, as a consequence, contributes to the regulation of important cellular activities, such as migration and proliferation.

PTHrP promotes malignancy of human oral cancer cell downstream of the EGFR signaling

“…3G-J). Recently, it is reported that PTHrP translocates into the nucleus and functions in an intracrine manner, which is associated with altered cell-cycle progression and protection from apoptosis [15][16][17]. We noted nuclear localization of PTHrP in addition to a cytoplasmic signal; however, PTHrP may not participate in apoptotic pathways in OSCC, since we found no cleaved Caspase-3, -9, or PARP in cells deficient in PTHrP (data not shown).…”

Parathyroid hormone-related protein expression, in combination with nodal status, predicts bone metastasis and prognosis of breast cancer patients

“…However, several studies have suggested PTHrP expression in the tumor might act against its progression, and be associated with better prognosis during early stage (15,23), and non-invasive breast cancer (16). Experimental analyses have also suggested that PTHrP has little involvement in the initial stages of metastasis (24,25). These observations suggest that PTHrP expression plays a role in preventing breast cancer progression while the disease remains in situ.…”

Activation of the receptor for parathyroid hormone and parathyroid hormone related protein induces apoptosis via the extrinsic and intrinsic signaling pathway

“…Besides the PTHlike domain, which lies within the N-terminal, part of the PTHrP protein, PTHrP contains two other functional domains, the mid-region and C-terminal domains. Post-translational cleavage of the PTHrP protein allows these domains to function independently (14)(15)(16)(17). By activation of PTH1R, the N-terminal parathyroid hormone-like domain stimulates protein kinase A (PKA), C (PKC), and/or the calcium-dependent pathways, respectively (17)(18)(19)(20).…”

“…Post-translational cleavage of the PTHrP protein allows these domains to function independently (14)(15)(16)(17). By activation of PTH1R, the N-terminal parathyroid hormone-like domain stimulates protein kinase A (PKA), C (PKC), and/or the calcium-dependent pathways, respectively (17)(18)(19)(20). The mid-region domain, containing a bipartite nuclear localization sequence at residues 88-91 and 102-106 and an importin ß-binding site at 66-94, can enter the nucleus and interfere with gene expression (17,(21)(22)(23)(24)(25).…”

“…By activation of PTH1R, the N-terminal parathyroid hormone-like domain stimulates protein kinase A (PKA), C (PKC), and/or the calcium-dependent pathways, respectively (17)(18)(19)(20). The mid-region domain, containing a bipartite nuclear localization sequence at residues 88-91 and 102-106 and an importin ß-binding site at 66-94, can enter the nucleus and interfere with gene expression (17,(21)(22)(23)(24)(25). The C-terminal domain physically interacts with ß-arrestin, which regulates internalization and desensitization of ligandstimulated G-protein-coupled receptors (26)(27)(28)(29)(30).…”