Interleukin-8 as a growth factor for human colorectal carcinoma cells in vitro.

Abstract

Interleukin-8 (IL-8’) is a member of the ‘C-X-C’ family of chemokines and has chemotactic activity for neutrophils and a subset of T cells. It is also capable of inducing a respiratory burst in peripheral blood neutrophils [I] . In addition, IL-8 can mediate angiogenesis [2] and, like the related C-X-C chemokine, melanoma growth stimulatory activity (gro), it can act as an autocrine growth factor for human melanoma cells [3]. Several human colorectal carcinoma cell lines constitutively produce IL-8 [4] and we have previously reported that tumour cells in the majority of human colorectal tumour specimens contain IL-8 mRNA and protein [5]. In the present experiments, the influence of exogenous IL-8 upon human colon carcinoma cell growth has been studied. In addition, the effect of neutralising constitutively produced IL8 upon cell growth has also been tested. The well-characterised human colon carcinoma cell lines HT29, CaCo2 and 116A were used as these have been reported to secrete IL-8 constitutively [4]. This was confirmed by measuring the IL-8 content of cell culture supernatants by ELISA. which showed that at confluence these lines constitutively produced up to lng/m1/24hr. This IL-8 was shown to be functional in both neutrophil chemotaxis and hen egg angiogenesis assays. The effect upon cell growth of adding exogenous rIL-8 to these cell lines was tested in a standard proliferation assay. Cells were plated in flat bottomed wells at 105/ml and grown for 3 days before adding rIL-8 for 2 days. Cultures were pulsed with ’H-thymidine for the final 4hr, harvested and counted. This led to a dose dependent growth stimulation of all cell lines (Table 1).