Bombesin (BBS) stimulates cellular proliferation of both normal and transformed cells. The mouse colon cancer cells (MC-26) possess specific binding sites for BBS. The purpose of this study, therefore, was to examine the effect of chronic administration of BBS on in vivo growth of MC-26 tumours in Balb/c mice and on survival of tumour-bearing mice. Three groups of mice (n = 10 each) inoculated with MC-26 cells received either saline containing 0.1% bovine serum albumin (BSA), or BBS (5 μg kg-1 or 20 μg kg-1) dissolved with 0.1% BSA saline by intraperitoneal route three times a day for 15 days. BBS increased weight, DNA and RNA contents of MC-26 tumours. To examine the effect of BBS on suŕvival rates of mice with MC-26 tumours, three groups of mice (n = 20 each) were treated for 31 days, as above. Onc group of mice inoculated with MC-26 cells received 0.1% BSA saline; the other group of MC-26-inoculated mice and the control group without tumour received BBS (5 μg kg-1) dissolved with 0.1% BSA saline. BBS significantly decreased the survival rate of mice bearing MC-26 tumours (median survival; saline group: 42.5 days, BBS group: 32.0 days, p = 0.037). None of the mice in the control group died during the experiment. BBS may stimulate in vivo growth of MC-26 cells through specific receptors.
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