Targeting the Multidrug Transporter Ptch1 Potentiates Chemotherapy Efficiency

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Multidrug resistance (MDR) is a major challenge in cancer chemotherapy.
• Overexpression of ATP-binding cassette (ABC) transporters is a key mechanism of MDR, but inhibitors face toxicity issues.
• Aberrant Hedgehog signaling and its receptor Ptch1 are implicated in chemotherapy resistance.

Purpose of the Study:

• To investigate the role of the Hedgehog receptor Ptch1 as a drug efflux pump in cancer.
• To identify and evaluate inhibitors of Ptch1's drug efflux activity.
• To assess the therapeutic potential of Ptch1 inhibition in combination with chemotherapy.

Main Methods:

• Characterization of Ptch1 as a proton motive force-dependent drug transporter.
• Screening chemical libraries to identify Ptch1 inhibitors.
• In vitro testing of Ptch1 inhibitors with chemotherapeutic agents in cancer cell lines.
• In vivo studies using mouse xenograft models of adrenocortical carcinoma.

Main Results:

• Ptch1 functions as a drug efflux pump, distinct from ATP-binding cassette transporters, utilizing the reversed pH gradient in cancer cells.
• Several molecules were identified that inhibit Ptch1 drug efflux activity, enhancing chemotherapy's cytotoxic effects.
• Combination therapy with a Ptch1 inhibitor and doxorubicin demonstrated superior efficacy in preventing tumor growth in vivo compared to doxorubicin alone, with no apparent toxicity.

Conclusions:

• Ptch1 is a novel, cancer-specific drug efflux pump and a viable therapeutic target.
• Inhibiting Ptch1 represents a promising strategy to overcome chemotherapy resistance in Ptch1-expressing cancers.
• Combination therapy with Ptch1 inhibitors offers a potential new approach for treating lung, breast, prostate, ovarian, colon, brain cancers, adrenocortical carcinoma, and melanoma.