Cyclin D1 is one of the proto‐oncogenes frequently amplified in cancer. The identification of its proto‐oncogenic role originated from studies on gene amplification, revealing its association with a chromosome inversion in parathyroid adenoma (PRAD1). It was also isolated from a human glioblastoma library using yeast genetic selection in G1‐cyclin depleted cells [31]. Here, PCNA is linked to glioblastoma.