A novel cross-talk between CXCR4 and PI4KIIIα in prostate cancer cells

Abstract

Chemokine signaling regulates cell migration and tumor metastasis. CXCL12, a member of the chemokine family, and its receptor, CXCR4, a G protein coupled receptor (GPCR), are key mediators of prostate-cancer (PC) bone metastasis. In PC cells androgens activate CXCR4 gene expression and receptor signaling on lipid rafts, which induces protease expression and cancer cell invasion. To identify novel lipid-raft-associated CXCR4 regulators supporting invasion/metastasis, we performed a SILAC-based quantitative proteomic analysis of lipid-rafts derived from PC3 stable cell lines with overexpression or knockdown of CXCR4. This analysis identified the evolutionarily conserved phosphatidylinositol 4-kinase IIIα (PI4KIIIα), and SAC1 phosphatase that dephosphorylates phosphatidylinositol-4-phosphate as potential candidate CXCR4 regulators. CXCR4 interacted with PI4KIIIα membrane targeting machinery recruiting them to the plasma membrane for PI4P production. Consistent with this interaction, PI4KIIIα was found tightly linked to the CXCR4 induced PC cell invasion. Thus, ablation of PI4KIIIα in CXCR4-expressing PC3 cells reduced cellular invasion in response to a variety of chemokines. Immunofluorescence microscopy in CXCR4-expressing cells revealed localized production of PI4P on the invasive projections. Human tumor studies documented increased PI4KIIIα expression in metastatic tumors vs. the primary tumor counterparts, further supporting the PI4KIIIα role in tumor metastasis. Furthermore, we also identified an unexpected function of PI4KIIIα in GPCR signaling where CXCR4 regulates PI4KIIIα activity and mediate tumor metastasis. Altogether, our study identifies a novel cross-talk between PI4KIIIα and CXCR4 in promoting tumor metastasis and suggests that PI4KIIIα pharmacological targeting may have therapeutic benefit for advanced prostate cancer patients.

Tumor Cell Dormancy and Reactivation in Bone: Skeletal Biology and Therapeutic Opportunities

“…Expression of CXCR4 has been shown to promote invasion and metastasis in melanoma, BCa, and PCa . This may be mediated through its effector protein phosphatidylinositol 4‐kinase IIIα (PI4KIIIα), which localizes to lipid rafts with CXCR4, contributing to tumor cell homing to metastatic sites and subsequent invasion . Furthermore, inhibition of the CXCL12–CXCR4 axis has been shown to compromise the establishment of PCa tumors in bone, while having no effect on pre‐established tumors in the skeleton .…”

Prostate Cancer

“…CXCR4 was constitutively up-regulated in metastatic breast cancer, liver, and lymph node. 70 In PC3 cells, the CXCL12a induces CXCR4 expression, mitogen activated protein kinase kinase (MAPKK/MEK):ERK NF-kB pathways pivotal in cancer cell proliferation. CXCR4 antibodies led to a suppression in the cancer proliferation and vascularization.…”

“…31 The CXCL12:CXCR4 axis leads to activation of several intracellular signaling pathways, leading to cellular migration and invasion; and the expression of CXCR4 is regulated by transmembrane protease serine 2 V-ets erythroblastosis virus E26 oncogene like (TMPRSS2-ERG) in PC. 70 A stable isotope labeling with amino acids in cell culture analysis on PC cells identified PI4KIIIa and SacI as CXCR4 interacting proteins that induced PC cell invasion. 70 The suppression of PI4KIIIa in CXCR4 expressing PC3 cells led to phosphatidylinositol-4-phosphate (PI4P) production and a reduction in the invasiveness.…”

“…70 A stable isotope labeling with amino acids in cell culture analysis on PC cells identified PI4KIIIa and SacI as CXCR4 interacting proteins that induced PC cell invasion. 70 The suppression of PI4KIIIa in CXCR4 expressing PC3 cells led to phosphatidylinositol-4-phosphate (PI4P) production and a reduction in the invasiveness.…”

“…70 Up-regulation of CXCR4 in PC leads to an enhancement in the invasive capacity of cancer cells, and its inhibition diminishes their metastatic ability. 70 Recent studies have gone on to suggest that CXCR4 could not only serve as a therapeutic target, but also a prognostic marker. The CXCL12:CXCR4 axis signals to promote colonization of cancer cells at metastatic sites in PC.…”