Claudin 18.2 protein is encoded by the CLDN18 gene, which belongs to the Claudin family of proteins and is one of the two important protein components of tight junctions.

Bulk data from West China Hospital in 2018 showed that the CLDN18-ARHGAP26/6 fusion gene was present in 8 (25%) patients with gastric indolent ring cell carcinoma, which had a worse prognosis and was not affected by chemotherapy, whereas patients who did not carry the CLDN18-ARHGAP26/6 fusion gene were able to achieve a survival benefit with chemotherapy. A review article published by Prof. Shen Lin in 2020 also pointed out that CLDN18-ARHGAP fusion gene in advanced gastric cancer is associated with poor prognosis and chemotherapy resistance, and more clinical studies are needed.

From the current data, the CLDN18 gene fusion does not seem to be strongly associated with its protein Claudin18.2 expression.