Autophagy and Mitochondrial Integrity in Tumorigenesis.
Research in the Macleod Lab seeks to understand and clarify the role of autophagy and mitochondrial dysfunction in tumor growth and progression to metastasis.
Autophagy is a well-conserved survival mechanismthat plays a cellular house keeping function in promoting the catabolic degradation of non-functional protein aggregates, organelles or pathogens by autolysosomes- “garbage disposal” – and thus plays a key role in maintaining cellular integrity and promoting efficient cellular function. Autophagy is also ramped up in response to energy deficits when it becomes critical for generating ATP and metabolites for survival.
Thus, not only is AUTOPHAGY the “garbage collector” – autophagy also promotes “re-cycling”.
The role of AUTOPHAGYin cancer is complex with evidence indicating it can act both as an anti-tumorigenic mechanism by inducing a growth arrest and cellular senescence, limiting genomic instability and maintaining organelle integrity while yet other data suggests that it can also be pro-tumorigenic by promoting tumor cell survival under hypoxia, allowing tumor cell dormancy at second sites that can lead to metastasis and limiting the therapeutic efficacy of anticancer treatments.
Work in the Macleod laboratory makes use of mouse models of cancer, in vivo imaging and clinical collaborations to explore the consequences of defective mitochondrial function and autophagy for tumor growth, progression to metastasis and cancer treatment.
Our work is specifically focused on the following goals:
how defects in mitophagy contribute to tumor progression to metastasis, including through altered responses to hypoxia, levels of reactive oxygen species, and tumor cell invasion;
how defects in mitophagy influence cellular metabolism and lipid catabolism in particular;
identify drugs that promote mitophagy in vivo and mitigate against the deleterious effects of tumor hypoxia;
use switchable mouse models of breast cancer to ask whether the role of autophagy in cancer varies depending on the stage of tumorigenesis;
examine the effect of inhibiting autophagy for tumor cell invasion and metastasis in vivo;
determine whether induction of autophagy can be used as a biomarker for tumor progression in human cancers;
assess the effect of inhibiting or promoting autophagy for cancer therapies in vivo.
The role of the RB tumor suppressor in oxidative stress responses and DNA damage control.
Oxidative stress is a major by-product of cellular metabolism and its regulation is critical for preventing disease and aging. Levels of reactive oxygen species (ROS) are generally higher in proliferating tumor cells than in normal cells and this may explain why ROS is a key component in the efficacy of chemotherapeutic drugs. Our work investigates the critical role played by the RB tumor suppressor in sensing and managing the response to increased ROS, through modulation of cell death regulators and induction of cell cycle checkpoints. We have shown that the RB tumor suppressor plays a pivotal role in determining the cytotoxic effect of chemotherapeutic drugs against tumor cells. By focusing on the role of the RB tumor suppressor in cellular stress responses and tissue homeostasis during normal development and in cancer, we aim to identify key mechanisms that will allow us to better understand the genesis of cancer and explore the efficacy of existing and novel therapeutics.
Specific research objectives in the Macleod Lab in this area include:
delineating the functional interaction between pRB and PARP-1 during cell cycle and in response to extrinsic sources of DNA damage;
use mouse models of breast cancer to examine how loss of Rb affects the response of tumors to genotoxic agents and Parp inhibitors in terms of oxidative stress, levels of DNA damage and tumor regression;
examine howloss of RB affectsthe outcome of different molecular sub-types of human breast cancer;
determine how loss of the RB tumor suppressor affectsDNA damage sensing/repair, genome instability and PARP inhibitor sensitivity in different molecular sub-types of human breast cancer.
Effects of Tumor-Specific Mutations on Re-programming the Ovarian Cancer Microenvironment.
We have recently established a collaboration with the laboratory of Dr. Ernst Lengyel to examine the role of specific tumor mutations in reprogramming the tumor microenvironment in mouse models of ovarian cancer. Using our expertise in targeted mouse models of cancer, combined with Dr. Lengyel’s expertise in ovarian cancer biology, we will determine whether specific tumor mutations are more or less effective than other mutations in converting normal ovarian stromal cells into cancer promoting stroma. Conversely, we will also examine how specific tumor mutations affect the ability of ovarian cancer cells to respond to key tumor stromal components, with particular emphasis on acquisition of invasive properties and metastasis.
Work in the Macleod laboratory is supported by the National Institutes of Health, the Department of Defense Breast Cancer Research Program, the Avon Foundation and the Ovarian Cancer Research Foundation.