PTHrP contributes to the anti-proliferative and integrin alpha6beta4-regulating effects of 1,25-dihydroxyvitamin D(3).
Parathyroid hormone-related protein (PTHrP) increases the growth and metastatic potential of prostate cancer cells, making it important to control PTHrP expression in these cells. 1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] suppresses PTHrP expression and exerts an anti-proliferative effect in prostate carcinoma cells. We used the human prostate cancer cell line C4-2 as a model system to ask whether down-regulation of PTHrP expression by 1,25(OH)(2)D(3) plays a role in the anti-proliferative effects of 1,25(OH)(2)D(3). Since PTHrP increases the expression of the pro-invasive integrin alpha6beta4, we also asked whether 1,25(OH)(2)D(3) decreases integrin alpha6beta4 expression in C4-2 cells, and whether modulation of PTHrP expression by 1,25(OH)(2)D(3) plays a role in the effects of 1,25(OH)(2)D(3) on integrin alpha6beta4 expression. Two strategies were utilized to modulate PTHrP levels: overexpression of PTHrP (-36 to +139) and suppression of endogenous PTHrP expression using siRNAs. We report a direct correlation between PTHrP expression, C4-2 cell proliferation and integrin alpha6beta4 expression at the mRNA and cell surface protein level. Treatment of parental C4-2 cells with 1,25(OH)(2)D(3) decreased cell proliferation and integrin alpha6 and beta4 expression. These 1,25(OH)(2)D(3) effects were significantly attenuated in cells with suppressed PTHrP expression. 1,25(OH)(2)D(3) regulates PTHrP expression via a negative vitamin D response element (nVDRE) within the noncoding region of the PTHrP gene. The effects of 1,25(OH)(2)D(3) on cell proliferation and integrin alpha6beta4 expression were significantly attenuated in cells overexpressing PTHrP (-36 to +139), which lacks the nVDRE. These findings suggest that one of the pathways via which 1,25(OH)(2)D(3) exerts its anti-proliferative effects is through down-regulation of PTHrP expression.
Shen
Xiaoli
X
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA.
Mula
Ramanjaneya V R
RV
Li
Jing
J
Weigel
Nancy L
NL
Falzon
Miriam
M
D002117:Calcitriol / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D039161:Integrin alpha6beta4 / Q000235:genetics / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D039161:Integrin alpha6beta4; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D002117:Calcitriol