Some of the pathogenic microorganisms have been associated with cancer due to the activation of cancer precursors in the host because of the inflammatory processes. Additionally, some other pathogens prevents the tumor formation by creating an anti-neoplastic immune response which has been reported to stop the development of cancer. Cystic echinococcosis (CE) or cyst hydatid disease (CHD) is a zoonotic infection caused by the larval form of Echinococcus granulosus sensu lato in humans. It has been reported that there is a negative correlation between E.granulosus infection and cancer and it has been suggested that direct and/or indirect E.granulosus infection may have an anti-cancer effect. However, the molecular mechanisms of this effect still remains unclear. The aim of this study was to evaluate the effect of hydatid cyst fluid administration on cell proliferation and expression of some apoptotic genes (BCL-2, p53 and BAX) in human healthy lung epithelial (BEAS-2B) and human lung adenocarcinoma (A549) cell lines and understanding the molecular mechanism underlying the possible anti-cancer action mechanism of hydatid cyst fluid. In order to evaluate the effect of hydatid cyst fluid on cell proliferation and apoptotic gene expression, cell proliferation assay (XTT) and real-time polymerase chain reaction (Rt-PCR) were performed, respectively. After the application of hydatid cyst fluid, there was no change in the cell proliferation. A statistically significant decrease in BCL-2 gene expression (> 90 fold) and an increase in p53 gene expression (> 1.2 fold) were found. No significant change in BAX gene expression was detected. In this study, it was found that the application of hydatid cyst fluid did not directly cause cell death but it has shown for the first time to sensitize the A549 cell line, which is resistant to apoptosisand shed light on the possible mechanism of hydatid cyst fluid in the apoptotic pathway.