The Mechanism of Rapamycin Resistance Development in Non-Cancerous Neural Progenitor Cells

The mTOR cellular pathway is at the forefront of research studies regarding cancer, autism, and post-injury recovery of the nervous system. Rapamycin is a well known inhibitor of TORC1 and is being investigated as a possible treatment treatment for many different types of cancers. Additionally, a derivative of rapamycin is used to treat Tuberous sclerosis complex, a disease typified by intellectual disability and benign tumors, which is caused by a defect in the mTOR pathway. However, rapamycin has limited use in glioblastoma multiforme (GBM), as GBM quickly develops resistance to chronic rapamycin treatment.

It has been shown in previously published research conducted in Dr. Harley Kornblum’s laboratory that GBM cell cultures become resistant to the antiproliferative effects of chronic rapamycin treatment through a downstream target of the mTOR pathway called MAP1B. It has been shown that MAP1B function is essential for the development of resistance to the anti-proliferative effects of rapamycin in glioblastoma cells. Epothilone D is a drug that increases microtubule stability. Due to the fact that resistance to chronic rapamycin is mediated by an induction of microtubule stability, a drug such as Epothilone D which promotes microtubule stability is predicted to make cells resistant to acute rapamycin treatment. Preliminary, unpublished research seems to show that the effects of rapamycin treatment on glioblastoma cell culture cell count are partially prevented by co-treatment with epothilone D. However, it is not known if this effect extends to non-cancerous tissue. To help confirm previous results and to examine if this pathway also exists in noncancerous cells, we plan to treat neural progenitor cells (NPCs) with varying doses of rapamycin and epothilone D. By observing the concurrent effects of rapamycin and epothilone D we can better understand the mechanism by which cells acquire resistance to chronic rapamycin treatment. We predict that the combination of rapamycin and epothilone D results in a decrease of the anti-proliferative effects of rapamycin, in comparison with cells treated with rapamycin alone. 

The primary methods utilized will be cell culture, such as care and maintenance of hESCs, differentiation of hESCs into NPCs, as well as cell counting via automatic cell counter, analysis of drug dose response, and techniques in experimental design.

The significance of this research lies in the understanding of the mTOR pathway and uncovering the mechanism of microtubule stability as a potential mechanism of resistance to drug therapies. By utilizing chemotherapeutic agents such as rapamycin and epothilone D the mTOR pathway can be better understood altered to help treat a variety of conditions, such as cancer, autism, CNS regeneration after injury, and peripheral nervous system injury.