As aberrant activation of PDK1 is thought to contribute to cancer progression and tumor cell invasiveness [9,27] and as PDK1phosphoS135 is detected in tumor cell lines, we performed immunofluorescence staining to detect this modification on cryosections of tumors resected from patients suffering from glioblastoma multiforme, a highly invasive brain cancer. The gene discussed is PDK1; the disease is brain cancer.