Despite progress in chemotherapeutic agents, non-small cell lung cancers (NSCLC) still have a poor survival rate. Thus, development of new therapeutic strategies, specifically against cancer cells is still required. For this purpose, we treated the non-small cell lung cancer cell line NSCLC-N6 with the natural product cucurbitacin D (CucD) - extracted from the plant Ecballium elaterium in order first to assess its in vitro cytotoxicity, but also to study the genetic changes that it could bring out. CucD has shown a blocking in the G1 phase of the cell cycle in NSCLC-N6 cells prior to apoptotic cell death. The reverse transcriptase-polymerase chain reaction-differential display (RT-PCR-DD) technique was also applied on treated cells to elucidate the genetic mechanisms involved. We revealed an overexpression of Cyclin-dependent kinase 1 (CDK1) mRNA after treatment and, with the use of antisense oligonucleotides, an effective role in the proliferation arrest of NSCLC-N6 cells. The present study provides new insights about the mechanisms of proliferation arrest in tumor cells and open new ways of treatment to target tumor growth.