Radiation induced conversion of GSCs into vascular cells

Background

Observation of glioblastoma (GBM) tumors post-radiation therapy shows an increase in vascular cells: namely endothelial cells (ECs) and pericytes (PCs). The significance of this research project lies in our ability to find the pathway through which GSCs differentiate into vascular cells post-radiation and target these pathways in order to decrease the likelihood of tumor growth and recurrence.

Hypothesis

Based on this observation, I hypothesize that radiation therapy induces glioblastoma stem cells (GSCs) to convert to ECs and PCs to promote tumor growth and recurrence. In accordance with my hypothesis, I expect that there will be an increase in the presence of these markers relative to the control group of tumors without radiation therapy.

Methods

To test this hypothesis, I will check EMT, hypoxia, fibroblast markers and EC specification genes in IRR GBM lines w/ and w/o IRR qPCR. The GBM recurrent line 296 is the cell line that will be utilized for this experiment.

Data 

	POU5F1/OCT4	KLF4	NEUN	CD68	IBA1	SOX2	OLIG2	PDGFRB	CD105	FSP1
0Gy	1	1	1	1	1	1	1	1	1	1
8 Gy	1.9	9.4	2.8	2	4.3	1.4	1.5	0.5	0.9	1.1
stdev	0.03	0.04	0.03	0.02	0.03	0.04	0.04	0.03	0.04	0.09
	0.06	0.03	0.05	0.07	0.2	0.02	0.03	0.06	0.1	0.08

	Twist1	Ncad	E-Cad	Snail	Slug	Hif1a	Hif2a	Pecam	Vwf	Desmin	aSMA	SM22a	Calponin	Iba1	GFAP
0 Gy	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
8 Gy	3.3	0.75	1.2	1.1	2.25	1.8	1.7	1.8	12.2	6.5	7.1	2	1.8	2.1	0.2
stdev	0.1	0.03	0.02	0.02	0.05	0.07	0.1	0.04	0.1	0.03	0.07	0.3	0.07	0.03	0.1
	0.05	0.02	0.02	0.09	0.09	0.07	0.03	0.07	0.4	0.4	0.5	0.1	0.07	0.1	0.01

Conclusions

As expected according to our observations and hypothesis, all 8Gy radiated cell lines showed an increase in the presence of the 25 genes that were tested. In particular, there are significantly large increases in the presence of KLF4, Vwf, and Desmin genes in the 8Gy radiated cells. The association between the KLF4 gene and the reprogramming pathway indicates that radiation is inducing GBM tumor cells to be reprogrammed into vascular cells. The significant increase of Desmin indicates that radiation may cause stem cells to differentiate into pericytes, which increase the viability of tumor recurrence. The increased presence of the Vwf gene indicates the greater potential for blood clot formation within endothelial cells surrounding the tumor. While my present data reflects the genetic indication of radiation resulting in the growth of endothelial vasculature that causes tumor recurrence, I hope to further research this cell line with Western blotting and immunostaining for EMT, fibroblast and EC/PC markers.