Small molecule targeting of cell ageing pathways to improve cancer treatment

Project: Research project

Grant Program

ORAU Grant

Project Description

A key goal in cancer therapy is to kill cancer cells without also killing the normal cells in the patient - a concept known as the therapeutic window. Although a long-term (and still elusive) "Holy Grail" has been the identification of agents that by themselves selectively kill cancer cells, a more recent and nuanced approach has been to seek secondary agents that selectively sensitize cancer cells to existing treatment regimens (eg chemotherapy with DNA damaging agents) when used in combination. This approach seeks to exploit knowledge of the consequences of the genetic lesions that are common in cancer cells that lead to altered cell behaviour, changes that might in turn be exploited for such a 'chemosensitization' approach. One such approach, which is the focus of this project, centres around the p53 tumour suppressor gene and the consequences of its frequent loss in cancer. In many cancer cells the G1 checkpoint is abrogated due to selection for lesions in tumour suppressor molecules such as p53 that regulate replicative senescence (Lehmann et al. 2012). Nevertheless, such cancer cells often retain a residual G2 checkpoint, in particular a chromatin-quality checkpoint in late G2 involving ATR/p38MAPK/MK2 (Reinhardt et al., 2007; Make et al., 2005; Mikhailov et al., 2004, 2005). Work using transgenic mice has recently demonstrated that genetic disruption of the p38/MK2 pathway specifically sensitizes p53-null mouse cells to DNA damaging agents (Reinhardt et al., 2007; Bucker et al., 2008; Morandell et al., 2013). The mechanism of action appears to be that the p53-null cells in the presence of ablation of p38/MK2 have lost both G1 and G2 DNA damage checkpoint function, and enter mitosis despite the presence of DNA damage, where they die by "mitotic catastrophe". In contrast, the p53 wild-type cells can still arrest in response to DNA damage even in the absence of p38/MK2 pathway function because the p53-dependent G1 checkpoint is still active. These cells halt in G1 and do not enter into mitotic catastrophe.
So, the overall objective is to test the hypothesis that small molecules inhibitors of the p38/MK2 stress signaling pathway alter the ability of cancer cells to respond to DNA damaging agents, potentially in a manner that might then make them of utility as chemosensitizing agents.

Key findings

1. Small cell lung cancer (SCLC) cell lines have been fully characterized for their growth, proliferative and cell cycle profile in the presence and absence of DNA damaging agents (chemotherapeutic drugs) and small molecules. These findings allowed us to understand the behavior of SCLC lines in vitro and explore dose response characteristics of cancer cells of interest.
2. Luciferase expressing cell lines have been generated using PLVT-Luc2 lentiviral particles and fully characterized for their growth characteristics using IVIS Spectrum CT. These cell lines will be used in an animal model to investigate the effect of small molecules on in vivo tumor suppression in Year 3 of the project.
3. Critically, in co-treatment experiments, the p38/MK2 kinase inhibitors SB203580 and MK2/3 (small molecules) both enhanced the negative effects of etoposide (DNA damaging agent) on H69 cell viability (Figure 1). Thus both p38 and MK2 inhibitors improved the sensitivity of H69 cells to DNA damaging agents. This is consistent with our initial hypothesis and theoretical framework and should be tested further in an animal model.
Short titleImproving cancer therapy
StatusFinished
Effective start/end date1/1/1512/31/17

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Cell Aging
Neoplasms
Therapeutics
DNA Damage
Null Lymphocytes
DNA
Tumor Suppressor Genes
Mitosis
Transgenic Mice
Chromatin
Drug Therapy