On his return to India, he joined the Indian Institute of Science (IISc) as a member of faculty at the division of biological sciences, subsequently became an associate professor at the Department of Microbiology and Cell Biology[3] and continues his association with IISc, serving as a professor.
[7] Somasundaram's work is centered around the studies of oncoviruses, tumor suppressor genes, gliomas and microRNAs and he has done advanced research on glioblastoma, an aggressive form of cancer affecting the brain.
[8][9] The group led by him is engaged in work concerning the determination of the role of cellular tumor antigen p53 in glioma, regulating the protein, p73 in cervical cancer patients, using Adenovirus early region 1A, a tumor suppressor gene, the analytical study of BRCA1 gene in breast cancer and the analysis and regulation of SV2A, a synaptic vesicle protein.
[3] He demonstrated that glioblastoma spreads rapidly by producing macrophage colony-stimulating factor (MCSF) in large quantities which in turn stimulate the growth of blood vessels in the tumor.
He serves as the principal investigator of the Genomics Programme of the IISc in collaboration with the New Millennium Indian Technology Leadership Initiative (NMITLI) of the Council of Scientific and Industrial Research (CSIR) and is the co-convener of the DBT - IISc Partnership Program for Advanced Research in Biological Sciences and Bio Engineering.