Breast Cancer Metabolism Research

• V. Krishnan Ramanujan, PhD

Our multidisciplinary approach involves development of high resolution, multimodality imaging approaches (two-photon excitation, fluorescence lifetime, spectral) for interrogating mitochondrial metabolism in vivo and single cell biophysical dynamics analysis approaches (pixel-by-pixel enzyme kinetics, fluorescence resonance energy transfer, nonlinear dynamical scaling analysis, time-series analysis), as well as unique breast cancer models with mitochondrial specific perturbations (genetic, pharmacological and small-molecule) and a variety of biochemical assays, proteomics and transcriptomics analyses of cancer-signaling pathways.

Time-Resolved Metabolic Imaging for Breast Cancer Detection and Therapeutic Guidance

We are currently developing and validating high-time-resolution metabolic imaging strategies for early detection of metabolic alterations in the transformed mammary epithelium. Our current efforts include:

• Establishing mammary epithelial cancer model systems with defined modulation of mitochondrial complex I function in estrogen receptor (ER)-positive and ER-negative breast cancer subgroups (human xenografts and transgenic mouse models). This will set the platform for understanding the role of mitochondrial complex I in two major breast cancer subgroups.
• Developing and validating time-resolved metabolic imaging strategies for monitoring alterations in mitochondrial complex I activity during the primary tumor progression in preclinical animal models and establishing correlation profiles between mitochondrial complex I function and degree of tumor aggressiveness.
  

Earlier attempts of metabolic imaging/redox spectroscopy systems have focused largely on steady-state fluorescence measurements. Time-resolved metabolic imaging strategies in multiple time scales, as proposed here, have an unique advantage in rapidly analyzing tumor metabolism without any contrast agents.

Mitochondrial Mechanisms of Redox Buffering and Chemosensitization of Breast Tumors

This is a relatively new research area that we are exploring in our laboratory. Impaired mitochondrial activity observed in many breast cancer cells renders them two selective advantages over their normal counterparts:

• An imbalance in mitochondrially generated reactive oxygen species (ROS) status, which in turn results in rewiring their adaptive response to an increased tolerance to the ROS (also called "redox buffering")
• An impaired mitochondrial apoptosis machinery, which in turn directly contributes to the commonly observed chemoresistance that is further exacerbated by the redox buffering events
  

Current strategies for tackling this problem include targeting the cellular redox poise (e.g., glutathione (GSH) redox status) using either inhibitors for GSH activity or its synthesis. Despite the direct and significant role of mitochondria in originating the observed redox buffering in breast cancer cells, there is little attention in the field toward targeting the mitochondrial redox status to address some of the aforementioned problems in breast cancer biology. Our current efforts in the laboratory are directed toward developing appropriate model systems and high-resolution metabolic imaging strategies for real-time monitoring of redox buffering and therapeutic responses in vivo.

• Ramachandran Murali, PhD
• Lali Medina-Kauwe, PhD
  
• Cathryn Kolka, PhD
  
• Roberta Gottlieb, MD
  
• Maria Lauda Tomasi, PhD
  

• Scaglione C, Xu Q, Ramanujan VK. Direct measurement of catalase activity in living cells and tissue biopsies. Biochem Biophys Res Commun. 2016 Jan 29;470(1):192-196. http://www.sciencedirect.com/science/article/pii/S0006291X16300262.
• Xu Q, Biener-Ramanujan E, Yang W, Ramanujan VK. Targeting metabolic plasticity in breast cancer cells via mitochondrial complex I modulation. Breast Cancer Res Treat. 2015 Feb;150(1):43-56. http://link.springer.com/article/10.1007%2Fs10549-015-3304-8.
• Ramanujan VK. Metabolic imaging in multiple time scales. Methods. 2014 Mar 15;66(2):222-229. http://www.sciencedirect.com/science/article/pii/S1046202313003423.
• Suhane S, Kanzaki H, Arumugaswami V, Murali R, Ramanujan VK. Mitochondrial NDUFS3 regulates the ROS-mediated onset of metabolic switch in transformed cells. Biol Open. 2013 Mar 15;2(3):295-305. http://bio.biologists.org/content/2/3/295.
• Nyirenda N, Farkas D, Ramanujan VK. Preclinical evaluation of nuclear morphometry and tissue topology for breast carcinoma detection and margin assessment. Breast Cancer Res Treat. 2011 Apr;126(2):345-354. http://link.springer.com/article/10.1007%2Fs10549-010-0914-z.