Nicolas Odartchenko

Expression of homeobox-containing genes in primary and metastatic colorectal cancer

Homeobox genes are a network of genes encoding nuclear proteins functioning as transcriptional regulators. Human and murine homeobox genes of the HOX family are organised in four clusters on different chromosomes. Gene order within each cluster is highly conserved, perhaps in direct relation to their expression. Homeobox genes have recently been involved in normal development and oncogenesis. We have analysed HOX gene expression in normal human colon and in primary and metastatic colorectal carcinomas. The majority of HOX genes are active in normal adult colon and their overall expression pattern is characteristic of this organ. Furthermore, the expression of some HOX genes is identical in normal and neoplastic colon indicating that these genes may exert an organ-specific function. In contrast, other HOX genes exhibit altered expression in primary colon cancers and their hepatic metastases which may suggest an association with colon cancer progression.

Growth stimulation of a human colorectal carcinoma cell line by interleukin-1 and -6 and antagonistic effects of transforming growth factor β1

We analysed the effect of interleukin-1 (IL-1), IL-6 and transforming growth factor beta 1 (TGF beta 1) on the growth of a panel of eight colorectal carcinoma cell lines. IL-1 stimulated growth of two lines (LS411N and LS1034) up to 20-fold and IL-6 enhanced proliferation of LS1034 more than 5-fold. Both cytokines also augmented colony-formation of LS1034 in methylcellulose. Under both growth conditions IL-1 was the most potent stimulator. However, the addition of IL-6 to IL-1 synergistically enhanced proliferation of LS1034 in monolayer culture and additively augmented the number of colonies formed in methylcellulose. Furthermore, TGF beta 1 strongly reduced the growth rate of LS1034. Low amounts of TGF beta 1 markedly inhibited the response of LS1034 to IL-1 and totally abrogated proliferation induced by IL-6. We conclude that different cytokines can provide distinct signals for the regulation of growth of colorectal carcinoma cells.

Binding, internalization and degradation of radio-iodinated interleukin 3 and granulocyte-macrophage colony stimulating factor by various hemopoietic cells

The proliferation and differentiation of hemopoietic committed progenitor cells depend on colony stimulating factors (CSF). However, isolated mouse granulocyte-macrophage progenitor cells can still undergo limited proliferation in serum-free cultures after CSF deprivation. To test whether this is due to an accumulated pool of internalized factor, we examined the binding, internalization and degradation of radiolabelled interleukin 3 (IL-3) and granulocyte-macrophage colony stimulating factor (GM-CSF) in various hemopoietic cells. We found 20,000 high affinity IL-3 receptors on cells of two IL-3-dependent hemopoietic cell lines, FDC-P1 and FDC-P2 (Kd = 85 and 129 pM). FDC-P1 cells, which also respond to GM-CSF, possess 600 high-affinity GM-CSF receptors (Kd = 64 pM). Cells of both lines internalize IL-3, but only FDC-P1 cells release degraded IL-3 at a rapid rate. Both cell lines have similar dose-response curves for IL-3 and survival kinetics after factor removal. All other cells tested behave like FDC-P1, suggesting that the metabolism of IL-3 by FDC-P2 is exceptional. Our study indicates that transient proliferation of committed progenitor cells in the absence of added factors is apparently not due to a stable pool of internalized CSF but merely represents an intrinsic capability of these cells.