PECAM1 and glioblastoma: The top 10 phosphopeptides identified included the same BTK pathway targets (Fig 4C); CD79A, PLCG1, PTN6, PECA1 ZAP70, and PLCG2 (38, 39, 40, 41, 42, 43), reinforcing the relevance of elevated BTK-associated kinase activity in lysates derived from GBM tissue.