Lysophosphatidic Acid Facilitates Proliferation of Colon Cancer Cells via Induction of Krüppel-like Factor 5

Abstract

Among the multiple cellular effects mediated by lysophosphatidic acid (LPA), the effect on cell proliferation has extensively been investigated. A recent study showed that LPA-mediated proliferation of colon cancer cells requires activation of ␤-catenin. However, the majority of colon cancer cells have deregulation of the Wnt/␤-catenin pathway. This prompted us to hypothesize the presence of additional pathway(s) activated by LPA resulting in an increase in the proliferation of colon cancer cells. Krüppel-like factor 5 (KLF5) is a transcriptional factor highly expressed in the crypt compartment of the intestinal epithelium. In this work, we investigated a role of KLF5 in LPA-mediated proliferation. We show that LPA stimulated the expression levels of KLF5 mRNA and protein in colon cancer cells and this stimulation was mediated by LPA 2 and LPA 3 . Silencing of KLF5 expression by small interfering RNA significantly attenuated LPA-mediated proliferation of SW480 and HCT116 cells. LPA-mediated KLF5 induction was partially blocked by inhibition of the mitogen-activated protein kinase kinase and protein kinase C-␦. Moreover, we observed that LPA regulates KLF5 expression via eukaryotic elongation factor 2 kinase (eEF2k). Inhibition of calmodulin or silencing of eEF2k blocked the stimulation in KLF5 expression. Knockdown of eEF2k specifically inhibited KLF5 induction by LPA but not by fetal bovine serum or phorbol 12-myristate 13-acetate. These results identify KLF5 as a target of LPA-mediated signaling and suggest a role of KLF5 in promoting proliferation of intestinal epithelia in response to LPA.

Regulation of Hypoxia-inducible Factor 1α (HIF-1α) by Lysophosphatidic Acid Is Dependent on Interplay between p53 and Krüppel-like Factor 5

“…As we showed previously, LPA stimulated proliferation of HCT116 cells via LPA 2 (Fig. 7, A and B) (23,34). Silencing of HIF-1␣ significantly attenuated the proliferation of HCT116 cells in the presence of LPA (Fig.…”

“…8A). To determine whether KLF5 plays a role in HIF-1␣ induction by LPA, HIF-1␣ induction was examined in cells treated with siRNA against KLF5 (23). Fig.…”

“…However, p53 is a negative regulator of HIF-1␣ transcription and not an inducer. We have shown previously that the transcription factor KLF5 plays an important role in the proliferation of colon cancer cells in response to LPA (23). Because silencing of either KLF5 or HIF-1␣ shows equally striking effects on HCT116 cell proliferation, we asked whether KLF5 has any role in HIF-1 regulation or vice versa.…”

“…Cell Culture and Plasmids-HCT116, LoVo, HT-29, and SW480 cells were grown as described previously (23).…”

Identification of an Insulin-regulated Lysophospholipase with Homology to Neuropathy Target Esterase

“…LPA is also a multifunctional phospholipid messenger. LPA controls growth, motility, and differentiation (45) and evokes various biologic effects, including neurogenesis (46), vasculogenesis (47), and carcinogenesis (48). Moreover, LPA plays an important role in the paracrine control of preadipocyte proliferation (41).…”