P-glycoprotein 1 as a shared target for resensitizing drug-resistant tumor cells and preventing fibronectin-driven metastasis.

RATIONALE: The exacerbation of chemoresistance and metastasis by synthetic cytotoxic reagents hinders effective cancer therapy, as these events often coincide and lead to poor clinical outcomes, yet are rarely targeted through a shared molecular mechanism. To address this, we established a mechanism-informed natural compound discovery strategy to identify a non-cytotoxic candidate with dual functionality, namely re-sensitizing drug-resistant tumor cells and preventing metastasis.

METHODS

Western blot, RT-qPCR, and flow cytometry were used for evaluating protein and mRNA expression, as well as cell apoptosis, while GC/MS and HPLC analyses for identifying active phytochemicals from extracts of traditional Chinese medicines. Therapeutic potential was validated in multiple mouse cancer models, including K-rasLSL-G12D/+; p53fl/fl mice. Clinical relevance was investigated via meta-analysis of associated gene signatures.

RESULTS

Mulberroside A (Mul A) from Cortex Mori Radices was identified as an ideal compound that inhibits P-glycoprotein 1 (Pgp1) in adherent tumor cells and pericellular fibronectin (periFN) assembly on suspended tumor cells (STCs), which drive drug resistance and metastasis, respectively. Using a paclitaxel (PTX)-resistant Lewis lung carcinoma cell line, we demonstrated that ERK-dependent Pgp1 functions as a shared upstream regulator of both chemoresistance and metastatic competence. Accordingly, Mul A inhibited Pgp1 mRNA and protein levels in an ERK-dependent manner, thereby differentially restoring PTX sensitivity both in vitro and in vivo, without intrinsic cytotoxicity, and significantly inhibiting lung metastasis by reducing the Pgp1-XIAP-periFN axis in STCs. Oral administration of Mul A achieved these dual anti-cancer effects in both experimental and spontaneous mouse models. Importantly, meta-analysis of clinical datasets further linked co-elevated FN and Pgp1 expression with poor prognosis and relapse in early-stage cancer patients, underscoring the translational relevance of targeting this shared pathway.

CONCLUSIONS

These findings identify Mul A as a promising non-cytotoxic therapeutic candidate and elucidate the shared upstream molecular mechanism linking distinct downstream chemoresistance and metastasis.