Lung cancer is the leading cause of cancer death worldwide and better therapies are required to treat this disease. Mcl-1, a pro-survival molecule is a member of the BCL-2 family of proteins involved in the intrinsic apoptotic pathway. It is amplified in many cancers, including lung cancer. Additionally, Mcl-1 is important during embryo development and its loss results in peri-implantation lethality. We propose that Mcl-1 may regulate survival of embryonic lung progenitor cells and deregulation may contribute to lung tumourigenesis. This study aims to characterise the role of Mcl-1 in lung development using a conditional knockout mouse model and to assess the dependency of lung cancer cells on Mcl-1 using CRISPR/Cas9.
We investigated expression of Mcl-1 during embryonic lung development and showed that it peaked at E17.5 and reduced after birth. To assess localisation of Mcl-1 in different cellular compartments of the lung, we used MCL-1 floxed mice carrying a hCD4 reporter crossed with Shh-cre mice. Using hCD4 as an indicator of MCL1 expression, combined with lung cell specific markers, we found that expression of Mcl-1 is restricted to epithelial cells. We are currently evaluating whether loss of Mcl-1 in the epithelium affects embryonic lung development.
We assessed the expression of Mcl-1 in several lung cancer cell lines. Western blots showed increased Mcl-1 in 6 out of 8 of the lines. We infected H1581, a large cell carcinoma cell line, with two different CRIPSR guide RNAs. Cloned single cell colonies showed loss of Mcl-1 by western blotting, and also resulted in cell death. Using CRISPR/Cas9, we are currently investigating which pro-apoptotic BH3-only protein is mediating cell death following loss of Mcl-1.
We have shown that Mcl-1 is expressed in the developing lung and in lung cancer cell lines where it is indispensible for survival. Future studies aim to elucidate the role of Mcl-1 in formation of the lung and how this process can be disrupted and contribute to carcinogenesis.