The gene SASH1 (SAM-and SH3-domain containing 1) has originally been identified as a candidate tumour suppressor gene in breast cancer. SASH1 is a member of the SH3-domain containing expressed in lymphocytes (SLY1) gene family that encodes signal adapter proteins composed of several protein -protein interaction domains. The other members of this family are expressed mainly in haematopoietic cells, whereas SASH1 shows ubiquitous expression. We have used quantitative real-time PCR to investigate the expression of SASH1 in tissue samples from 113 patients with colon carcinoma, and compared the expression with 15 normal colon tissue samples. Moreover, nine benign adenomas and 10 liver metastases were analysed. Expression levels of SASH1 were strongly and significantly reduced in colon cancer of UICC stage II, III, and IV, as well as in liver metastases. Moreover, SASH1 was also found to be downregulated on protein levels by immunoblot analysis. However, SASH1 expression was not significantly deregulated in precancerous adenomas and in earlier stage lesions (UICC I). Overall, 48 out of 113 primary colon tumours showed SASH1 expression that was at least 10-fold lower than the levels found in normal colon tissue. Downregulation of SASH1 expression was correlated with the formation of metachronous distant metastasis, and multivariate analysis identified SASH1 downregulation as an independent negative prognostic parameter for patient survival. This study demonstrates for the first time that expression of a member of the SLY1-gene family has prognostic significance in human cancer.

Background:Patients with UICC/AJCC stage II colon cancer have a high 5-year overall survival rate after surgery. Nevertheless, a significant subgroup of patients develops tumour recurrence. Currently, there are no clinically established biomarkers available to identify this patient group. We applied reverse-phase protein arrays (RPPA) for phosphatidylinositide-3-kinase pathway activation mapping to stratify patients according to their risk of tumour recurrence after surgery.Methods:Full-length proteins were extracted from formalin-fixed, paraffin-embedded tissue samples of 118 patients who underwent curative resection. RPPA technology was used to analyse expression and/or phosphorylation levels of six major factors of the phosphatidylinositide-3-kinase pathway. Oncogenic mutations of KRAS and BRAF, and DNA microsatellite status, currently discussed as prognostic markers, were analysed in parallel.Results:Expression of phospho-AKT (HR=3.52; P=0.032), S6RP (HR=6.3; P=0.044), and phospho-4E-BP1 (HR=4.12; P=0.011) were prognostic factors for disease-free survival. None of the molecular genetic alterations were significantly associated with prognosis.Conclusions:Our data indicate that activation of the PI3K/AKT pathway evidenced on the protein level might be a valuable prognostic marker to stratify patients for their risk of tumour recurrence. Beside adjuvant chemotherapy targeting of upregulated PI3K/AKT signalling may be an attractive strategy for treatment of high-risk patients.

We previously produced pigs with a latent oncogenic TP53 mutation. Humans with TP53 germline mutations are predisposed to a wide spectrum of early-onset cancers, predominantly breast, brain, adrenal gland cancer, soft tissue sarcomas and osteosarcomas. Loss of p53 function has been observed in >50% of human cancers. Here we demonstrate that porcine mesenchymal stem cells (MSCs) convert to a transformed phenotype after activation of latent oncogenic TP53R167H and KRASG12D, and overexpression of MYC promotes tumorigenesis. The process mimics key molecular aspects of human sarcomagenesis. Transformed porcine MSCs exhibit genomic instability, with complex karyotypes, and develop into sarcomas on transplantation into immune-deficient mice. In pigs, heterozygous knockout of TP53 was sufficient for spontaneous osteosarcoma development in older animals, whereas homozygous TP53 knockout resulted in multiple large osteosarcomas in 7–8-month-old animals. This is the first report that engineered mutation of an endogenous tumour-suppressor gene leads to invasive cancer in pigs. Unlike in Trp53 mutant mice, osteosarcoma developed in the long bones and skull, closely recapitulating the human disease. These animals thus promise a model for juvenile osteosarcoma, a relatively uncommon but devastating disease.