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Mitotic checkpoint protein hsMAD2 as a marker predicting liver metastasis of human gastric cancers
1The Second Department of Surgery, Mie University School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan. qouji@clin.medic.mie-u.ac.jp.
Abstract:
hsMAD2, the human homologue of mitotic arrest deficient 2 (MAD2), is a key component of the mitotic checkpoint system. Recently, mutations and decreased expression of mitotic checkpoint genes including hsMAD2 have been reported in cancer cell lines with defective mitotic checkpoint. However, the genetic alterations in the genomic hsMAD2 gene have not been determined in gastric cancers. Moreover, the biological implications of the overexpressed hsMAD2 in primary cancers are unknown. In this study, we analyzed 32 primary gastric cancers with polymerase chain reaction (PCR) amplification of all exons, including flanking intronic sequences, of the genomic hsMAD2 gene followed by direct DNA sequencing. We also measured the hsMAD2 protein levels in cancer and normal tissues by semi-quantitative immunoblotting. No mutations were found in the coding sequences, although three single nucleotide polymorphisms (SNPs) were identified in the noncoding sequences in 13 of 32 patients. These SNPs were not associated with either hsMAD2 expression or disease progression. The semi-quantitative western blot analysis showed hsMAD2 was significantly overexpressed in gastric cancer tissues compared with corresponding normal tissues (P < 0.001). The calculated ratio of the hsMAD2 protein in cancer tissue (C) to that in corresponding normal tissue (N) (C / N ratio) was significantly higher in patients with well differentiated adenocarcinoma (P = 0.0274) or with synchronous liver metastasis (P = 0.0025). A C / N ratio greater than 3 was observed more frequently in patients with synchronous liver metastasis. Therefore, C / N ratio > 3 may be clinically important as a predictive indicator for metachronous liver metastasis of gastric cancers.
Insights
Overexpression of human MAD2 (hsMAD2) protein is common in gastric cancers, correlating with tumor differentiation and liver metastasis. Elevated hsMAD2 may predict metastasis, aiding clinical management of gastric cancer.
Area of Science:
- Molecular biology
- Oncology
- Genetics
Background:
- The human homologue of mitotic arrest deficient 2 (hsMAD2) is crucial for the mitotic checkpoint.
- Mutations and reduced hsMAD2 expression are observed in cancer cell lines with faulty mitotic checkpoints.
- Genetic alterations and biological implications of hsMAD2 in gastric cancer remain largely unknown.
Purpose of the Study:
- To investigate genetic alterations in the genomic hsMAD2 gene in gastric cancers.
- To determine the expression levels of hsMAD2 protein in gastric cancer tissues.
- To explore the clinical significance of hsMAD2 overexpression in gastric cancer progression and metastasis.
Main Methods:
- Genomic DNA from 32 primary gastric cancers was analyzed using PCR amplification of all exons and flanking intronic sequences, followed by direct DNA sequencing.
- hsMAD2 protein levels were quantified in cancer and adjacent normal tissues via semi-quantitative immunoblotting.
- Statistical analyses were performed to correlate hsMAD2 alterations and expression with clinicopathological features.
Main Results:
- No mutations were detected in the coding regions of the hsMAD2 gene; however, three single nucleotide polymorphisms (SNPs) were found in noncoding sequences in 13 of 32 patients.
- These SNPs did not correlate with hsMAD2 expression levels or disease progression.
- hsMAD2 protein was significantly overexpressed in gastric cancer tissues compared to normal tissues (P < 0.001).
- Higher hsMAD2 protein ratios (cancer vs. normal tissue) were associated with well-differentiated adenocarcinoma (P = 0.0274) and synchronous liver metastasis (P = 0.0025).
- A cancer/normal hsMAD2 ratio greater than 3 was more frequent in patients with synchronous liver metastasis.
Conclusions:
- The genomic hsMAD2 gene does not harbor mutations in gastric cancers, but noncoding SNPs exist without clear clinical impact.
- hsMAD2 is significantly overexpressed in gastric cancer, with elevated levels linked to tumor differentiation and liver metastasis.
- An hsMAD2 protein ratio > 3 may serve as a valuable predictive indicator for metachronous liver metastasis in gastric cancer patients.
