RhoA, Claudin 18, and c-MET in Gastric Cancer: Clinicopathological Characteristics and Prognostic Significance in Curative Resected Patients

Molecular alterations in claudin 18 suppressed and non-suppressed gastric adenocarcinomas to guide targeted therapies

BACKGROUND

Gastric adenocarcinoma represents an aggressive type of cancer and an important cause of cancer mortality. Progress in gastric cancer therapeutics has resulted from a better understanding of the molecular pathogenesis of the disease and introduction of targeted therapies, but most gastric cancer patients still rely on non-targeted chemotherapy as the mainstay of treatment for advanced disease.

METHODS

An analysis of publicly available series from The Cancer Genome Atlas (TCGA) gastric cancer cohort was undertaken to delineate the clinical and genomic landscape of gastric cancers with suppressed expression of claudin 18 compared with cancers with non-suppressed claudin 18. Claudin 18 suppressed cancers were defined as having an mRNA expression z-score relative to normal samples (log RNA Seq V2) of less than -1. Claudin 18 non-suppressed cancers were defined as having an mRNA expression z-score relative to normal samples (log RNA Seq V2) above 0.5.

RESULTS

Gastric cancers with claudin 18 mRNA suppression represented 7.7% of the gastric adenocarcinomas of TCGA cohort, while non-suppressed cancers represented 46.6% of the cases. The two groups did not differ in clinical and genomic characteristics, such as mean age, histology, grade, and stage. The mutation landscape of claudin 18 suppressed cases included high mutation rates of TP53, of genes of the WNT/β-catenin pathway and of ubiquitin ligase FBXW7. Moreover, a subset of both claudin 18 suppressed and non-suppressed cancers displayed mutations in Mismatch Repair (MMR) associated genes or a high tumor mutation burden (TMB). At the mRNA expression level, claudin 18 suppressed gastric cancers showed up-regulation of EMT core transcription factor Snail 2 and down-regulation of genes of HLA cluster. The survival of gastric cancer patients with claudin 18 mRNA suppression was not significantly different compared with patients with non-suppressed claudin 18.

CONCLUSION

Sub-sets of gastric cancers with claudin 18 mRNA suppression displayed characteristics of potential therapeutic interest, such as mutations in WNT and PI3K pathways and MMR defects. These may guide the development of alternative targeted therapies, in this sub-set of gastric cancers which are not candidates for claudin 18 targeting therapies.

Targeting CLDN18.2 in cancers of the gastrointestinal tract: New drugs and new indications

Cancers of the gastrointestinal (GI) tract greatly contribute to the global cancer burden and cancer-related death. Claudin-18.2(CLDN18.2), a transmembrane protein, is a major component of tight junctions and plays an important role in the maintenance of barrier function. Its characteristic widespread expression in tumour tissues and its exposed extracellular loops make it an ideal target for researchers to develop targeted strategies and immunotherapies for cancers of the GI tract. In the present review, we focus on the expression pattern of CLDN18.2 and its clinical significance in GI cancer. We also discuss the tumour-promoting and/or tumour-inhibiting functions of CLDN18.2, the mechanisms regulating its expression, and the current progress regarding the development of drugs targeting CLDN18.2 in clinical research.

Study on the expression of c-Met in gastric cancer and its correlation with preoperative serum tumor markers and prognosis

Background

Studies have found that c-Met plays a critical role in the progression of solid tumors. This study aimed to investigate the expression of c-Met in gastric cancer (GC) and its correlation with preoperative serum tumor markers and prognosis, in order to provide a more theoretical basis for targeting c-Met in the treatment of GC.

Methods

Ninety-seven patients who underwent curative gastrectomy in our hospital from December 2013 to September 2015 were included in this study. The tissue microarray was constructed by paraffin-embedded tumor tissue of enrolled patients, including 97 GC points and 83 paracancerous points. Then, it was used for c-Met immunohistochemical staining, followed by an immunological H-score. The clinical baseline data and 5-year survival of patients with low and high c-Met expression were compared. Besides, the correlation between the expression of c-Met in tumor tissues and preoperative serum tumor markers was investigated. Finally, multivariate Cox regression analysis was used to explore the survival risk factors of patients.

Results

c-Met has a high expression rate in GC tissues 64.95% (63/97). The expression of c-Met was significantly different in different clinicopathological stages (p < 0.05); the high expression group also had a higher M stage and clinicopathological stage of GC. The correlation test between the c-Met H-score and CA125 was statistically significant (p = 0.004), indicating a positive correlation. Furthermore, high c-Met expression correlated with poor overall survival (OS) for 5 years (p = 0.005). It was also found that the high expression of c-Met in stage I–II patients was correlative with poor OS for 5 years (p = 0.026), while stage III–IV patients had no statistical significance (p > 0.05). Multivariate Cox regression analysis showed that c-Met might be an independent risk factor for survival 5 years after surgery.

Conclusion

This study found that the high expression of c-Met in GC tissues was associated with poor 5-year OS in GC patients and was an independent risk factor for 5-year survival after curative gastrectomy. The expression of c-Met in GC tissues was also positively correlated with preoperative serum CA125.