Proliferation and differentiation of a human colon cancer cell line (CaCo2) is associated with significant changes in the expression and secretion of insulin-like growth factor (IGF) IGF-II and IGF binding protein-4: role of IGF-II.

Abstract

The extent to which the insulin-like growth factor (IGF) system contributes to the initiation and progression of colon cancer remains poorly defined. We recently reported that a majority of human colon cancers express and secrete the potent mitogen IGF-II and at least two inhibitory binding proteins, IGFBP-2 and IGFBP-4. In the present study we measured the expression and secretion of IGF-II, IGFBP-2, and IGFBP-4 in relation to growth and differentiation of CaCo2 human colon cancer cells, which undergo spontaneous enterocytic differentiation in culture. Under the conditions of the present study, CaCo2 cells demonstrated an initial rapid phase of growth between Day 2 through days 7-9 of culture, followed by a significant retardation in the growth between days 9-13. Alkaline phosphatase (ALP) activity, a marker of enterocytic differentiation, progressively increased between Days 7-13 in culture, temporally correlating with post-confluent phase of negligible growth. These changes in growth and differentiation were accompanied by > 80% decline in the relative concentration of IGF-II messenger RNA (mRNA) between Days 2-13. In contrast, the relative mRNA concentrations of inhibitory binding proteins (IGFBP-2 and IGFBP-4) increased rapidly to 200% of Day 2 values by Days 5-7 before returning to baseline levels by Day 13. The relative protein concentrations of the three factors measured in the conditioned media of the cells followed a pattern very similar to that measured for the mRNA levels. While the changes in the relative protein concentrations and mRNA levels of IGF-II and IGFBP-4 were statistically significant, the changes measured in the RNA and protein levels of IGFBP-2 were not, as a result of large inter experimental variations. Thus these results suggested that CaCo2 cell differentiation may require an attenuation of IGF-II effects. To confirm the latter possibility, additional studies were conducted with a specific neutralizing antibody against IGF-II. Incubation of CaCo2 cells with anti-IGF-II antibodies from Day 0 through Day 7 significantly retarded the growth of the cells and was accompanied by a significant increase in the concentration of Alkaline phosphatase activity per 10(6) cells. Recently, we reported a potent inhibitory role of IGFBP-4 in the growth of colon cancer cells. In the present studies, a possible important role of IGF-II is illustrated not only in the growth but also in the differentiation of colonic cells. Our studies thus suggest that differential expression of IGF-II and IGFBPs may be playing a critical role in both proliferation and differentiation of colonocytes.

Liver Regeneration Stimulates Tumor Metastases

“…IGFs play a critical role in regulating cell growth and death through interaction with the main IGF receptor (IGF-R) which is overexpressed in certain cancers [41]. IGF I and II are strong mitogens for a wide variety of cancer cell lines including cancers of the colon, breast, liver and lungs [31,[41][42][43]. IGF-I has been found to increase the tendency of cancer cells to metastasise [44].…”

Differential Expression and Biological Effects of Insulin-like Growth Factor-binding Protein-4 and -5 in Vascular Smooth Muscle Cells

“…In human colon cancer CaCo2 cells, which express and secrete IGF-II and IGFBP-2 and IGFBP-4, proliferating cells express abundant IGF-II and low quantities of inhibitory IGFBP-4, while differentiated cells secrete abundant IGFBP-4 and virtually undetectable IGF-II (32). In MC3T3-E1 murine osteoblasts, IGFBP-2 and IGFBP-4 are produced at their highest concentrations in differentiated cells, while IGFBP-5 production is higher in proliferating cells (33).…”

Interleukin-5 potentiates the growth response of Caco-2 cells to IGF-II: A role in colonic carcinogenesis complicating ulcerative colitis?

“…Increases have been shown in IGFBP-1 (2.5-fold), IGFBP-2 (3-to 5-fold), IGFBP-3 (8-fold) with reductions in IGFBP-4 (0.5-to 2-fold) following differentiation [16,[20][21][22].…”