Cisplatin selects for multidrug-resistant CD133⁺ cells in lung adenocarcinoma by activating notch signaling

Platinum-based chemotherapy is the first-line treatment for non-small cell lung cancer, but recurrence occurs in most patients. Recent evidence suggests that CD133⁺ cells are the cause of drug resistance and tumor recurrence. However, the correlation between chemotherapy and regulation of CD133⁺ cells has not been investigated methodically. In this study, we revealed that CD133⁺ lung cancer cells labeled by a human CD133 promoter-driven GFP reporter exhibited drug resistance and stem cell characteristics. Treatment of H460 and H661 cell lines with low-dose cisplatin (IC₂₀) was sufficient to enrich CD133⁺ cells, to induce DNA damage responses, and to upregulate ABCG2 and ABCB1 expression, which therefore increased the cross-resistance to doxorubicin and paclitaxel. This cisplatin-induced enrichment of CD133⁺ cells was mediated through Notch signaling as judged by increased levels of cleaved Notch1 (NICD1). Pretreatment with the g-secretase inhibitor, N-[N-(3,5-difluorophenacetyl)-1- alanyl]-S-phenylglycine t-butyl ester (DAPT), or Notch1 short hairpin RNAs (shRNA) remarkably reduced the cisplatin-induced enrichment of CD133⁺ cells and increased the sensitivity to doxorubicin and paclitaxel. Ectopic expression of NICD1 reversed the action of DAPT on drug sensitivity. Immunohistochemistry showed that CD133⁺ cells were significantly increased in the relapsed tumors in three of six patients with lung cancer who have received cisplatin treatment. A similar effect was observed in animal experiments as cisplatin treatment increased Notch1 cleavage and the ratio of CD133⁺ cells in engrafted tumors. Intratumoral injection of DAPT with cisplatin treatment significantly reduced CD133⁺ cell number. Together, our results showed that cisplatin induces the enrichment of CD133 ⁺ cells, leading to multidrug resistance by the activation of Notch signaling.