Copper-chelator exerts synergistic interaction with platinum drugs through modulating copper transporters in oxaliplatin-resistant human gastric cancer cell

[[abstract]]Although platinum-based chemotherapy drugs including cisplatin, carboplatin, and oxaliplatin are commonly used in the treatment of human solid tumor, patients ultimately develop drug-resistance and result in treatment failure. Combination copper-chelator with platinum drugs has been reported to successfully treat a subset of cisplatin- resistant ovarian cancer patients. However, the underlying mechanisms of action remain unknown. We have previously established an oxaliplatin-resistant subclone from human gastric adenocarcinoma TSGH cells, S3. The mechanisms responsible for oxaliplatin resistance of S3 cells included down-regulation of hCtr1 and over-expression of ATP7A. In contrast to displaying additive to antagonistic interaction with platinum drugs in parental, TSGH cells, our studies showed that copper-chelator, D-penicillamine, exerts synergistic interaction with platinum drugs through increasing platinum- DNA adduct formations in S3 cells. D-penicillamine promotes copper uptake transporter hCtr1 expression via activation of transcription factor Sp1. In addition, Sp1 overexpression promotes p53 translocation from nucleus to cytosol and binds to ubiquitin, and finally causes p53 degradation, which further suppressed the expression of copper efflux transporter, ATP7A. Combination of D-penicillamine and oxaliplatin significantly inhibited S3 cell growth in animal model. Immunohistochemical analysis showed that up-regulation of hCtr1 and down-regulation of ATP7A were found in both D-penicillamine- and D-penicillamine/ Oxalipatin- treated S3 tumors, which were consistence to in vitro results. In conclusion, our results showed that D-penicillamine increases hCtr1 expression through regulating Sp1 level. Notably, D-penicillamine could down-regulate ATP7A expression through regulation of p53. Our finding demonstrated a new treatment strategy for cancer patient resistant to oxaliplatin treatment with low expression of hCtr1 and overexpression of ATP7A in tumor tissues