Men with colorectal cancer are predisposed to prostate cancer.

BACKGROUND: The objective of the present study was to investigate the relationship between colorectal and prostate cancer. METHODS: All Victorian men who developed metachronous colorectal and prostate cancer with the first primary diagnosed between 1982 and 1993 were identified retrospectively from the Victorian Cancer Registry and were followed up to the end of 1995. Analyses were stratified by age group and years of follow up. The cause of death in those men who had prostate cancer following colorectal cancer was determined. The stage of colorectal cancer was compared between men with and without second primary prostate cancer and the grade of prostate cancer was compared with men who did not have a prior colorectal cancer. RESULTS: Men who develop colorectal cancer are at increased risk of prostate cancer, with the greatest risk in men under the age of 65 (Relative risk approximately 2). Men with first primary colorectal cancer are more likely to develop prostate cancer than colorectal second primaries, and men who develop second primary prostate cancer are more likely to die of prostate cancer than colorectal cancer. CONCLUSIONS: Younger men diagnosed with colorectal cancer are at increased risk of prostate cancer. However, there is no direct evidence that screening for prostate cancer leads to a reduction in mortality. This should be considered when discussing long-term follow up.

SH2-Bbeta is a Rac-binding protein that regulates cell motility.

The Src homology 2 (SH2) domain-containing protein SH2-Bbeta binds to and is a substrate of the growth hormone (GH) and cytokine receptor-associated tyrosine kinase JAK2. SH2-Bbeta also binds, via its SH2 domain, to multiple activated growth factor receptor tyrosine kinases. We have previously implicated SH2-Bbeta in GH and platelet-derived growth factor regulation of the actin cytoskeleton. We extend these findings by establishing a potentiating effect of SH2-Bbeta on GH-dependent cell motility and defining regions of SH2-Bbeta required for this potentiation. Time-lapse video microscopy, phagokinetic, and/or wounding assays demonstrate reduced movement of cells overexpressing SH2-Bbeta lacking an intact SH2 domain because of a point mutation or a C-terminal truncation. An N-terminal proline-rich domain (amino acids 85-106) of SH2-Bbeta is required for inhibition of cellular motility by SH2 domain-deficient mutants. Co-immunoprecipitation experiments indicate that Rac binds to this domain. GH is shown to activate endogenous Rac, and dominant negative mutants of SH2-Bbeta are shown to inhibit membrane ruffling induced by constitutively active Rac. These findings suggest that SH2-Bbeta is an adapter protein that facilitates actin rearrangement and cellular motility by recruiting Rac and potentially Rac-regulating, Rac effector, or other actin-regulating proteins to activated cytokine (e.g. GH) and growth factor receptors.