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Investigation of a dependency of RAS-driven cancers on matrix metalloproteinase-7

Final Report Summary - RAS AND MMP7 (Investigation of a dependency of RAS-driven cancers on matrix metalloproteinase-7)

Cancer is a leading cause of death worldwide. Tumourigenesis is thought to proceed via the accumulation of genetic errors, often leading to the activation of proto-oncogenes or inactivation of tumour suppressor genes. Mutations of the RAS proto-oncogene contribute to the formation of a large proportion of human tumours. In fact, 20 % of human tumour samples carry activating mutations in the KRAS, NRAS or HRAS oncogenes.

RAS proteins have proved impossible to inhibit selectively using drugs and tumours with activating RAS mutations tend to be resistant to most targeted therapies. In order to find new strategies to treat tumours harbouring KRAS mutations, the objective of the project is the identification of genes necessary for the KRAS-driven oncogenic state. Tumourogenic state depends on the activities of a variety of genes and pathways, many of which are not oncogenic themselves. Importantly, these genes and pathways are essential to support the oncogenic phenotype of cancer cells but are not required to the same degree for the viability of normal cells. Thus, inhibition of these pathways could selectively kill cells harbouring KRAS mutations without affecting normal cells. However, some of these genes or pathways are not obvious and have not been identified. To identify these pathways we have used two different approaches a whole genome scale ribonucleic acid (RNA) interference screen and a drug screen.

The RNA interference screen allowed the identification of several genes that are required for the survival of KRAS transformed cells but not for normal cells with wild-type KRAS. Initially, we focused our project in the study of the mechanism of dependency of cells with KRAS mutations on the matrix metalloproteinase-7 (MMP-7) expression. However, in a most exhaustive study we found that the effect of MMP-7 was due to specific off-target effects. For this reason, we decided to study other hits obtained in the same screen. We have demonstrated that cancer cells expressing oncogenic KRAS are highly dependent on the transcription factor GATA2, the deoxyribonucleic acid (DNA) replication initiation regulator CDC6 and proteasome and topoisomerase activities. The analysis of the mechanisms of this dependency has allowed us to identify new therapeutic strategies to treat tumours harbouring KRAS mutations. Treatment of protease inhibitors together with Rho signalling or topoisomerase inhibitors produces an improved killing of KRAS mutant cells.

As second approach we used a panel of 25 non-small cell lung cancer (NSCLC) cell lines, half of which carry an activating KRAS mutations and tested the effect of more than 50 small molecule inhibitors. Interestingly, cells harbouring an activated KRAS oncogene were more sensitive to MEK, RAF and IGF1R inhibitors than cells carrying only wild-type KRAS alleles. Moreover, combinations of IGF1R inhibitors with MEK or RAF inhibitors resulted in a synergistic anti-proliferative effect in KRAS mutant cell lines and also show improved effectiveness in autochthonous mouse models of Kras induced NSCLC. Mechanistically, we have demonstrated that activation of PI3K in KRAS mutant NSCLC cells is controlled by a coordinate input from KRAS and IGF1R proteins.

In summary, the results obtained during the Intra-European Fellowship have allowed us to identify new genes necessary for the Ras-driven oncogenic state. We have demonstrated that cells harbouring KRAS mutations are dependent on the expression of transcription factor GATA2, the DNA replication initiation regulator CDC6. Moreover, these cells are also more sensitive to the inhibition of MEK, IGF1R, proteasome and topoisomerase activities. Interestingly, these findings have suggested new potential strategies for tumours harbouring KRAS mutations.

Cancer is the major cause of morbidity in the European Union (EU). Basic research is the base for applied science to find and improve treatments for illnesses. Thus, projects like this, which have identified new pharmacological targets to treat tumours harbouring KRAS mutations, will contribute to Europe scientific excellence. Moreover, this knowledge can lead to collaboration with companies to explore the design of new drugs based in the new findings. However, once a candidate novel target for drug development has been identified a significant period must inevitably elapse until such potential therapy reaches clinical trials. Interestingly, our findings have also suggested new potential drug combinations using compounds that are already available and / or in clinical use. Thus, we have also been able to propose immediately applicable therapeutic strategies to treat KRAS mutant tumours.