Preclinical Model Systems to Study GBM and AML
In Vitro Approach
With the aim of simulating the brain-like microenvironment in terms of mechanosensing properties for studying the cell-ECM interactions in vitro, we have taken advantage of polyacrylamide hydrogels system to mimic the substrate stiffness existing in the brain microenvironment. Using this hydrogel model developed in collaboration with Dr. Abhijit Majumder at IIT, Bombay, we have seen that relapse cells show different morphology on softer substrates as compared to the parent, and have enhanced single cell velocity, proliferation rate, invasion, and chemoresistance as seen in clinical settings. Additionally, EGFR is known to be amplified in 30% of GBM patients and contributes to the aggressive phenotype of the tumor, the hydrogel model, could also capture this clinical phenotype EGFR is upregulated only in the relapse cells seeded on a softer substrate. Currently, we are analyzing the role of EGFR in the mechanosensing properties of relapse GBM cells with respect to ECM stiffness. Furthermore, we are examining the role of cell-cell interactions in 3D culture conditions, wherein we have observed that the relapse cells form more tight and compact clumps as compared to the parent cells, which form loose aggregates. We are now trying to deduce the molecular pathways that may be involved in the crosstalk between cell adhesion and survival in relapse cells.
In Vivo Approach
In order to decode the underlying molecular mechanisms responsible for GBM therapy resistance and recurrence in vivo, we have established orthotopic mouse models by intracranial injections of GBM cell lines and patient samples (patient-derived orthotopic xenografts). The superiority of orthotopic models lies in their higher ability to recapitulate the original tumor. A detailed understanding of these resistance mechanisms can help to develop novel therapeutic regimes, which can potentially prevent or delay tumor recurrence and significantly improve patient survival. Similarly, in the case of Acute Myeloid Leukemia (AML), despite the achievement of complete morphological remission in 60-70% of cases, most of them relapse. The presence of less than 5% of bone marrow blasts serve as a post-therapy prognosticator and is termed as the minimal residual disease (MRD) state, presence of residual cells has been reported to be correlated with poor therapy response and survival, thereby suggesting a vital role of these residual cells in resistance and relapse. However, a complete understanding of the active resistance mechanisms in these residual AML cells formed in vivo is lacking. Thus, we are developing a preclinical mouse model to recapitulate the clinical scenario of MRD state in order to examine the molecular mechanisms of resistance in these MRD cells.