6277

S100A6

S100 calcium binding protein A6;S100A6;S100 calcium binding protein A6

MLN 4|S100 calcium-binding protein A6 (calcyclin)|calcyclin|growth factor-inducible protein 2A9|prolactin receptor-associated protein|protein S100-A6

1q21

protein-coding

OBJECTIVE: S100A6 and S100A4, two of S100 protein family, have been suggested to be associated with cancer tumorigenesis and metastasis. The aim of this study was to evaluate the expression levels of S100A6 and S100A4 in matched samples of primary human colorectal adenocarcinomas (T), adjacent normal colorectal mucosa (N) and liver metastases (M). This gave us the advantage of directly comparing levels of S100A6 and S100A4 expression within the same genetic background. METHODS: In matched samples of N, T and M from 10 colorectal adenocarcinoma patients, expressions of S100A6 and S100A4 were studied by Western blot and immunohistochemical analyses using specific antibodies against each protein. RESULTS: The expression levels of S100A6 were significantly higher in T than in N (p < 0.05), while those of S100A4 showed no difference between T and N. There were no significant differences in the expression levels of S100A6 or S100A4 between M and T. Similar results were obtained by immunohistochemical analysis. Moreover, S100A6 was stained more intensely in invading fronts than in central portions of both T and M. CONCLUSIONS: The observed differential expression of S100A6 and S100A4 suggests that S100A6, rather than S100A4, is associated with human colorectal adenocarcinoma tumorigenesis and invasion/metastasis.

OBJECTIVE: Some members of the S100 gene family have been suggested to be associated with cancer development and metastasis. Our previous cDNA micro-array studies have showed S100A6 expression is elevated in gastric cancer compared with that in paired normal mucosa. To validate our previous results and further investigate the possible role of S100A6 gene in gastric cancer, we carried out this detailed S100A6 expression analysis in more matched gastric cancer samples. METHODS: S100A6 expression was detected in 20 paired fresh surgical samples of gastric tumor tissue and matched non-cancerous mucosa by QRT-PCR. A gastric cancer tissue microarray (TMA) containing 1020 duplicate matched normal mucosa, gastric cancer tissue and metastatic lymph node tissue cores from 208 gastric cancer patients was constructed. S100A6 expression was detected by immunohistochemistry and the correlation between S100A6 expression with clinicopathological factors and survival was analyzed. RESULTS: As quantitated by QRT-PCR, S100A6 transcript level was elevated in 73.7% of the primary cancer lesions with an average 2.25-fold up-regulation than that in matched non-neoplastic mucosa. As displayed by immunohistochemistry, the positive rate of S100A6 in non-neoplastic mucosa, tumor lesions and metastatic lymph nodes was 34.3%, 84.1% and 90.9%, respectively. S100A6 expression level in cancer and metastatic lymph node was significantly higher than their matched non-neoplastic mucosa (P < 0.05). 65.5% of patients showed an increased S100A6 expression in cancer tissue compared with that in matched normal mucosa. S100A6 overexpression was associated with larger tumor size and deeper invasion (P = 0.022 and P = 0.009). No evidence was found for an association between S100A6 expression level and other variables, including tumor grade, nodal metastases, and TNM stage. There was no association between S100A6 expression level and survival. But compared with paired non-neoplastic mucosa, an increased S100A6 expression in tumor lesion predicated a decreasing suvival if compared with a decreased S100A6 expression, though the difference was statistically not significant. CONCLUSION: Elevated expression of S100A6 gene may be an early event in the development and progression of gastric cancer. Further study of this gene may be helpful for understanding the nature of gastric carcinoma.

While most osteosarcoma patients have metastatic or micrometastatic lesions, less than 15% of them have clinically detectable metastatic diseases at presentation. To identify potential markers that may predict osteosarcoma metastasis, we analyzed the expression of S100A6 in 50 osteosarcoma cases and found that 84% of the analyzed specimens stained positive for S100A6. There is a trend towards decreased clinically evident metastasis with increased S100A6 staining. Overexpression of S100A6 in osteosarcoma cells decreases cell motility and anchorage independent growth on collagen gels. Our findings provide evidence that, while S100A6 is commonly overexpressed in human osteosarcoma, loss of its expression correlates with a metastatic phenotype.

There is a critical need to identify markers that can accurately identify existing or predict future metastatic disease in patients with osteosarcoma since the majority of patients present with undetectable micrometastatic disease. We previously reported S100A6 is overexpressed in human osteosarcoma and increased expression of S100A6 by immunohistochemistry correlated with decreased clinical metastasis. We have established 11 primary cultures from biopsies of patients with osteosarcoma and ten of the 11 primary cultures have increased expression of S100A6 relative to normal human osteoblasts. To further explore possible mechanisms for metastasis suppression previously reported, we used in this report siRNA-mediated knockdown of S100A6 in four commonly used human osteosarcoma lines, then examined their cell adhesion, migration, and invasion properties. Knockdown of S100A6 expression inhibited cell adhesion and promoted cell migration and invasion in these lines. Conversely, S100A6 overexpression enhanced cell adhesion and inhibited cell invasion. Our data demonstrate S100A6 is commonly overexpressed in human osteosarcoma. S100A6 may inhibit osteosarcoma metastasis by promoting cell adhesion and inhibiting cell motility and invasion. Thus, S100A6 may be considered a potential marker for human osteosarcoma with prognostic value for identifying patients without metastases.

In papillary thyroid carcinoma (PTC), metastasis is a feature of an aggressive tumor phenotype. To identify protein biomarkers that distinguish patients with an aggressive tumor behavior, proteomic signatures in metastatic and non-metastatic tumors were investigated comparatively. In particular, matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) was used to analyze primary tumor samples. We investigated a tumor cohort of PTC (n = 118) that were matched for age, tumor stage, and gender. Proteomic screening by MALDI-IMS was performed for a discovery set (n = 29). Proteins related to the discriminating mass peaks were identified by 1D-gel electrophoresis followed by mass spectrometry. The candidate proteins were subsequently validated by immunohistochemistry (IHC) using a tissue microarray for an independent PTC validation set (n = 89). In this study, we found 36 mass-to-charge-ratio (m/z) species that specifically distinguished metastatic from non-metastatic tumors, among which m/z 11,608 was identified as thioredoxin, m/z 11,184 as S100-A10, and m/z 10,094 as S100-A6. Furthermore, using IHC on the validation set, we showed that the overexpression of these three proteins was highly associated with lymph node metastasis in PTC (p < 0.005). For functional analysis of the metastasis-specific proteins, we performed an Ingenuity pathway Analysis and discovered a strong relationship of all candidates with the TGF-beta-dependent EMT pathway. Our results demonstrated the potential application of the MALDI-IMS proteomic approach in identifying protein markers of metastasis in PTC. The novel protein markers identified in this study may be used for risk stratification regarding metastatic potential in PTC.