Milk derived exosomes sensitize Gefitinib-resistant lung cancer cells to Pemetrexed via CAV1-mediated endocytosis.

Lung cancer patients resistant to EGFR-TKIs often demonstrate a decreased response to Pemetrexed. Therefore, it is urgent to explore the mechanisms of drug resistance and develop new strategies. We investigated the potential of milk-derived exosomes as drug carriers, focusing specifically on pemetrexed encapsulated in these exosomes. We isolated exosomes from milk and loaded them with pemetrexed through electroporation to form a drug delivery carrier named as mExoPEM. Then, we examined how mExoPEM exerts anti-tumor effects in Gefitinib-resistant lung cancer cells, as well as the molecular mechanisms involved. Gefitinib-resistant cells were insensitive to the cytotoxicity of pemetrexed, due to the drug reflux caused by the elevated P-glycoprotein. When co-cultured with mExoPEM, resistant cells demonstrated enhanced anti-tumor responses in vitro and in vivo. Moreover, mExoPEM facilitated cellular uptake via Caveolin-1 (CAV1)-mediated endocytosis, which was regulated by the PPARγ/CAV1 pathway. Notably, pioglitazone, a PPARγ agonist, augmented mExoPEM uptake and synergized with mExoPEM to inhibit the proliferation of resistant cells. In conclusion, our study presents a promising strategy to address pemetrexed resistance in GR lung cancer cells through the use of milk exosome as drug carriers. Moreover, we elucidate the molecular mechanism underlying pemetrexed resistance and its enhanced delivery via milk exosome-mediated endocytosis.