Differential contribution of the ERK and JNK mitogen-activated protein kinase cascades to Ras transformation of HT1080 fibrosarcoma and DLD-1 colon carcinoma cells

Abstract

Although an important contribution of ERK and JNK mitogen-activated protein kinase (MAPK) activation in Ras transformation of rodent ®broblasts has been determined, their role in mediating oncogenic Ras transformation of human tumor cells remains to be established. We have utilized the human HT1080 ®brosarcoma and DLD-1 colon carcinoma cell lines, which contain endogenous mutated and oncogenic N-and K-ras alleles, respectively, to address this role. Study of these cells is advantageous over Ras-transformed rodent model cell systems for two key reasons. First, the ras mutations occurred naturally in the progression of the tumors from which the cell lines were derived, rather than due to overexpression of an exogenously introduced gene. Second, although these tumor cells possess defects in multiple genetic loci, it has been established that mutated Ras contributes signi®cantly to the transformed phenotype of these cells. Clonal variant lines of HT1080 and DLD-1 have been isolated which have lost the oncogenic ras allele and exhibit a corresponding impairment in growth transformation in vitro and in vivo. We found that upregulation of Raf/MEK/ERK and JNK correlated with expression of oncogenic Ras in HT1080, but not DLD-1 cells. Furthermore, inhibition of ERK activation in parental HT1080 cells caused the same changes in cell morphology and actin stress ®ber organization seen with loss of expression of activated NRas(61K). Thus, we suggest that constitutive activation of the Raf/MEK/ERK and JNK pathways is necessary for Ras-induced transformation of HT1080 but not DLD-1 cells. These results emphasize that cell type di erences exist in the signaling pathways by which oncogenic Ras causes transformation.

MST4, a new Ste20-related kinase that mediates cell growth and transformation via modulating ERK pathway

“…Likewise, constitutively active ERK was shown to be su cient to elicit cell transformation (Greulich et al, 1996;Huang et al, 1999;Plattner et al, 1999;Verheijen et al, 1999). These ®ndings are in good agreement with our results that MEK1/ERK activation by MST4 is the underlying cause of cellular transformation induced by MST4.…”

Intrinsic resistance to the MEK1/2 inhibitor AZD6244 (ARRY‐142886) is associated with weak ERK1/2 signalling and/or strong PI3K signalling in colorectal cancer cell lines

“…43 However, KRAS 13D appears to drive malignancy by different pathways in these cells, since HCT116 cells exhibit strong P-ERK1/2 but little or no P-PKB, whilst AZD6244-resistant DLD-1 cells exhibit modest activation of both pathways; the weak activation of ERK1/2 in DLD-1 has been reported previously. 44 This difference is even more apparent in resistant SW837 cells, which exhibit very strong P-PKB but very low activation of ERK1/2. In this context, it is perhaps relevant to think in terms of 'pathway addictionÕ as well as 'oncogene addiction'; both HCT116 cells and DLD-1 cells are addicted to KRAS 13D , 43 but only HCT116 cells exhibiting strong activation of ERK1/2 have evolved to be addicted to that pathway and are therefore sensitive to AZD6244.…”

Physiology and Pathophysiology of Proteinase-Activated Receptors (PARs): PAR-2-Mediated Proliferation of Colon Cancer Cell

“…There have been cumulative evidences demonstrating the proliferation-stimulating effects of PARs on fibroblasts (12), vascular endothelial cells, and smooth muscle cells in vitro (13 -18). In this minireview, we described the effects of PAR-1 or PAR-2 stimulation by the respective agonist proteinase and activating peptide on the intracellular Ca 2+ signaling and proliferation of DLD-1, a human colon carcinoma cell line (19,20). We found that PAR-1 and PAR-2 stimulation induced a similar transient [Ca 2+ ] i signal, but only PAR-2 stimulation induced cell proliferation through the activation of MEK1 / 2-ERK1 / 2.…”