selleck inhibitor As with disease-free survival, the difference was of borderline statistical significance (P=0.056). This suggests SMAD4 as a predictive marker for 5FU/mitomycin adjuvant chemotherapy Figure 2 Kaplan�CMeier plotting of survival in response to 5FU therapy in patients (n=202) with SMAD4 deletion (top) and with no loss of SMAD4 (bottom). Overall survival (left): HR=3.23, 95% CI=0.97�C10.8, P=0.056. … DISCUSSION We established that among the patients with colorectal cancer involved in this study, SMAD4 was deleted in 67% of cases. These results, obtained by gene copy dosage, are consistent with those deduced from earlier cytogenetic (Vogelstein et al, 1988; Mitelman et al, 1997) and loss of hetereozygocity (LOH) studies on the 18q21 region (Laurent-Puig et al, 1992; Jen et al, 1994; Mart��nez-L��pez et al, 1998; Jernwall et al, 1999; Watanabe et al, 2001).

However, these LOH studies are frequently based on microsatellite markers that span several centiMorgans (cM), and therefore several megabases (Mb). In contrast to that approach, our strategy allows for a more refined analysis by targeting an individual gene rather than a wide chromosomal region that certainly contains a number of important genes. Thus, it is likely that an analysis at the single gene level will give a more accurate image of eventual clinical implications of genetic alterations. We observed that colorectal cancer patients with normal SMAD4 gene copy status had a three-fold higher benefit of 5FU-based therapy than those with SMAD4 deletion.

This result is consistent with the previous observation by Watanabe et al (2001), that patients with retention of 18q21 alleles had a benefit of 5FU-based chemotherapy of the same order as was found in this study. Moreover, refinement of deletion studies from the chromosomal band level to the gene level may provide a clue to possible mechanisms through which 18q21 deletion influences the outcome of patients with CRC. Therefore, our results reinforce the hypothesis that TGF�� and its signalling components have a role in tumour suppression. This result also suggests the definition of SMAD4 as a predictive marker for benefit of 5FU-based chemotherapy in patients with colorectal cancer. Finally, these findings suggests a mode of action of this cytostatic compound that is SMAD4-dependent.

Thus, the integrity of this component of the TGF��/BMP pathway is not only required for cytokine signalling, but may also be an important factor for 5FU-mediated apoptosis. In addition to the requirement of functional apoptotic pathways such as CD95/Fas (Houghton et al, 1997), bax (Rampino et al, 1997) and p53 (Vogelstein et al, 2000) for drug sensitivity in GSK-3 colorectal tumour cells, this suggests that integrity of the TGF�� pathway may be an additional condition for efficiency of 5FU treatment. Thus, our results provide an additional clue to the genetic basis of drug resistance in cancer.