The present results suggest that Smad4 gene is one of true targets of 18qLOH, and that its inactivation is involved in advanced stages, such as distant metastasis, in human colorectal carcinogenesis.
Although SMAD4 mutations have been associated with late-stage or metastatic disease, our combined molecular and cytogenetic data best fit a model in which SMAD4 mutations occur before colorectal cancers become aneuploid/polyploid, but after the MSI(+) and MSI(-) pathways diverge.
Because resistance to anoikis in tumor cells is thought to contribute to metastasis, our data suggest a functional basis for the strong correlation between defects in Smad4 and development of malignancy.
In this study, we evaluated the effect of restoring chromosome 18 on metastasis in a few human pancreatic cancer cell lines with and without inactivation of SMAD4.
Communication of MDA-MB-231 cells with the bone microenvironment, which is needed for optimal tumor cell growth and metastasis, may be affected in Smad4 knockdown cells as TGF-beta-induced expression of interleukin 11 was attenuated on Smad4 knockdown.
Absence of Smad4 protein was more frequently observed in hepatic metastases, whether they were metachronous or synchronous, than in extrahepatic metastases (p<0.005).
Chromosome 18q21 deletion and Smad4 protein inactivation have been reported as molecular markers predicting unfavorable outcome in colorectal cancers and, in a previous report, we recently revealed that these molecules are closely associated with distant metastasis, which is one of the clinical factors affecting postoperative survival.
This study suggests that SMAD4 is an important marker for confirming a diagnosis of pancreatic adenocarcinoma as a primary tumor, as well as when it presents as a metastatic tumor on small fine-needle aspirate samples.
However, Dpc4 immunolabeling status of carcinoma tissues harvested at autopsy, a sensitive marker of DPC4 genetic status, was highly correlated with the presence of widespread metastasis but not with locally destructive tumors (P = .007).
The data suggested that restoration of Smad4 in Smad4-deficient cells may provide a potential therapeutic strategy for intervention of colon cancer migration and metastasis.
Smad4 expression in the cases with lymphatic metastasis was lower than the cases without metastasis (P<0.01), whereas Smad7 expression in the cases with lymphatic metastasis was much higher than the case without metastasis (P<0.01).
TGF-beta induced migration/invasion, tumorigenicity, and metastasis of Smad4-null MC38 and SW620 cells; incubation with LY2109761 reversed these effects.
Results from current work implicate Smad4 might suppress the invasion and metastasis of human ovarian tumor cells through a TGF-Beta/Smad-mediated pathway.
Follow-on pathological and functional assessment confirmed cyclin D1 and SPP1 as key mediators of these biological processes, which together with PTEN and SMAD4, form a four-gene signature that is prognostic of prostate-specific antigen (PSA) biochemical recurrence and lethal metastasis in human PCA.
Murine tumors show enrichment of the TGF-β/SMAD4 network, and genetic validation studies confirmed the cooperative roles of Pten, p53, and Smad4 deficiencies in prostate cancer progression, including skeletal metastases.
Matched primary and metastasis tissues were evaluated for intragenic mutations in KRAS, CDKN2A, and TP53 and immunolabeled for CDKN2A, TP53, and SMAD4 protein products.
In human tumor samples, there was a strong inverse correlation between levels of CCL15 and SMAD4; metastases that expressed CCL15 contained 3-fold more CCR1(+) cells than those without CCL15.
Out of 73 patients, there was cytoplasmic reactivity: of TGF-β1 in 37 (50.7%); of Smad4 in 62 (84.9%); of Smad7 in 46 (63%), and of TGFβRII in 39 (53.4%) of the metastases.
Our results demonstrate that stem cells with Kras(G12D) activation and Smad4 depletion can produce tumors that are multipotent and susceptible to EMT and metastasis.
Pharmacological inhibition with TGF-β receptor kinase inhibitors or tumour specific Smad4 knockdown disturbed invasion and metastasis in the zebrafish xenograft model and closely mimicked the results we obtained with these cells in a mouse metastasis model.