BMP4 and glioblastoma: However, the three mechanisms of action: basic VACV oncolytic activity of initially infected GBM CSCs, growth inhibition by secreted BMP-4 from these that results in differentiation and facilitation of second and third round infections of the differentiated GBM CSCs resulting in greater oncolytic activity causes significant cellular growth inhibition that translates into tumor growth inhibition in brains of mice implanted with the GBM CSCs.