Early events in colorectal tumorigenesis include mutation of the adenomatous polyposis coli (APC) gene and epigenetic hypermethylation with transcriptional silencing of the O(6)-methylguanine DNA methyltransferase (MGMT), human mut L homologue 1 (hMLH1), and P16/CDKN2A genes.
To further explore intestinal regional responses, we studied effects of sulindac on additional gene-targeted mouse models of human intestinal tumorigenesis; these were (i) Apc(1638N/+) mouse (chain termination mutation in exon 15 of the Apc gene); (ii) Mlh1(+/-) mouse (DNA mismatch repair deficiency, a mouse model of human hereditary non-polyposis colorectal cancer) and (iii) double-heterozygous Mlh1(+/-)Apc(1638N/+) mutant mouse.
Our findings therefore reveal a reciprocal suppression mechanism between FZR1 and BRAF in controlling tumorigenesis.<b>Significance:</b> FZR1 inhibits BRAF oncogenic functions via both APC-dependent proteolysis and APC-independent disruption of BRAF dimers, whereas hyperactivated ERK and CDK4 reciprocally suppress APC<sup>FZR1</sup> E3 ligase activity.
Experiments were designed to assess the chemopreventive effects of a novel dual 5-LOX/COX inhibitor, licofelone {[6-(4-chlorophenyl)-2,2-dimethyl-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl] acetic acid}, in APC(Min/+) mouse intestinal tumorigenesis.
In this study, we investigated the effects of pentoxifylline on inflammation-related colon tumorigenesis in a rodent model using Kyoto APC delta rats, which have APC mutation and are susceptible to colon carcinogenesis.
Furthermore, we found that adenomas bearing truncated Apc had increased beta-catenin activity when compared with tumors lacking Apc protein, which could lead to context-dependent inhibition of tumorigenesis.
To clarify the molecular mechanisms of human carcinogenesis associated with abnormal beta-catenin/T-cell factor (Tcf) signaling, we have been using cDNA microarrays to search for genes whose expression is significantly altered after introduction of wild-type APC into SW480 colon cancer cells.
Finally, we discuss future research directions to further elucidate the physiological contributions of APC/C components during tumorigenesis and validate their potentials as a novel class of anti-cancer targets.
These data suggest that more than one gene on chromosome 5q21 may contribute to colorectal carcinogenesis and that mutations at the APC gene can cause both adenomatous polyposis coli and Gardner's syndrome.
Since activating mutations in the beta-catenin gene have similar effects on the biochemical level as inactivating mutations in the tumor suppressor gene APC, it is speculated that beta-catenin mutations may substitute APC gene inactivation in carcinogenesis.
Crossing APC(Min/+) with Jagged1(+/Delta) mice is sufficient to significantly reduce the size of the polyps arising in the APC mutant background indicating that Notch is an essential modulator of tumorigenesis induced by nuclear beta-catenin.
These results indicate that ras oncogene mutations are related to the progression of prostate cancer, whereas APC gene alteration is not involved in tumorigenesis and development of this cancer.
The adenomatous polyposis coli (APC) gene product is involved in cell cycle arrest and apoptosis, and loss of function is associated with the development of colorectal carcinogenesis.
These data support a novel mechanism in which p.Glu1317Gln in combination with other weak mutant APC alleles (generating polypepetides with zero, two, or three 20AARs) can provide the necessary growth advantage for colorectal tumorigenesis.
Therefore, although allelic loss at the APC locus is frequent in squamous cell carcinomas of the esophagus, it is likely that a gene on 5q other than APC is involved in esophageal tumorigenesis.
Our results indicate that nuclear activation of β-catenin is a late event in the tumorigenesis of nephroblastomas coinciding in some tumours with LOH of the APC gene.
Thus, APC mutation-induced up-regulation of the survivin/ABK cascade can explain delayed crypt cell maturation, expansion of proliferative cell populations (including mitotic figures), and promotion of colon tumorigenesis.