Impact of Stretching on Tumor growth and Metastasis

National Institute Of Dental & Craniofacial Research

Investigators

Abstract

Cancer is among the most serious health problems worldwide, and this situation urges multiple efforts to develop new more effective and less toxic treatments. There has been interest in developing non-pharmacological treatments that could boost natural defenses against cancer and contribute to primary and secondary cancer prevention. Among these, exercise has received a significant amount of attention due to the well-documented positive association between physical activity and survival in many cancer types. However, to date, physical modalities are not used specifically to modify the process of tumor formation. Animal studies of exercise in cancer models have yielded mixed results. Furthermore, these studies have involved levels of vigorous aerobic exercise that can be difficult to achieve in cancer patients. On the other hand, gentle movement-based techniques such as yoga, tai chi and qi gong are popular and well tolerated among cancer patients for managing symptoms and improving mobility and well-being. Stretching of tissues is a component of these techniques that has not been extensively studied but could have important effects on the cancer itself. Our recent studies show that gentle daily stretching for 10 minutes can have profound effects on reducing local connective tissue inflammation and fibrosis in several rodent models, via direct mechanical effects on the stretched tissues. We have also demonstrated a 52% reduction of mammary tumor growth over one month in mice undergoing stretching for 10 minutes once a day, without any other form of therapy. In this project, we will use this animal model aiming to: A) Explore the impact of stretching on tumor growth and the progression to metastasis. B) Investigate the mechanisms of the effect of stretching on tumor growth. The effect of Stretching is being tested in the polyoma middle T (MMTV-PyVmT) mouse breast cancer model, which is highly metastatic. We have important data suggesting a significant effect of stretching on tumor growth. We have used dual photon second harmonic (SHG) imaging to visualize tumor collagen structure and extracellular matrix: Cell lines carrying polyoma middle T transgene (Met-1) were GFP tagged using a Lentiviral plasmid system to track the implanted tumors. Images of the entire tumor and its surroundings have been taken. We have observed that stretched mice had more benign tumor-associated collagen signatures (TACS) compared with non-stretched mice, with more collagen fibers oriented parallel (<15 degrees), and less fibers oriented perpendicular (>75 degrees) to the tumor boundary. This finding indicates that stretching impacts the organization of collagen fibers around the tumor, which has been shown to be a key factor influencing cancer progression. PYMT Transgenic model: We have stablished a new stretching model under anesthesia, that will impact the tumors locally, by stretching the animals horizontally on supine position. A third Stretching model has been developed, where mice orthotopically injected with a breast cancer cell line (Met-1), are randomly assigned to home cage phenotyper, adapted so food pellets and water are at low level (No stretch) while the other group is housed in a phenotyper cage where water and food are at higher level, so animals need to "spontaneously stretch" (Stretching group) to reach the food and water. The system allows 24/7 video monitoring, which will be used to quantify animal behavior. GOALS: Explore mechanism of stretching using single cell RNAseq Use CT scanning to quantify lung metastasis. Explore translational potential of these models to the human condition. We have observed in this spontaneous stretching model, a reduction of the size of the tumors implanted in FVB mice In vitro model: Using 2D and 3D cultures from a breast cancer cell line (Met-1), we have established an in vitro model to study the effect of stretching at cellular level. We have developed 3D cultures with Met-1 (PYMT cell line), which organize into spheroids that are embedded into collagen gels. Collagen embedded-spheroids are either stretched or not stretched and analyzed for biological markers such as Ki-67, caspase-3, progesterone receptor, estrogen receptor, cadherin. GOALS: Use flow cytometry, scRNAseq and rheology to investigate mechanism of stretching Measure biologics markers in spheroids We have found a reduction in spheroid crown area after three days of stretching, compared with no stretching. We are investigating the potential relationship of spheroid crown area to markers to changes in collagen gel stiffness following stretching.