We also observed that in LGG more core-clock genes were significantly correlated whereas in GBM these significant correlations were lost pointing to a stronger disruption of the core-clock network in GBM (Fig. 4A). Notably, our results suggested that the co-expression of PER family genes (PER1, PER2 and PER3) showed the most drastic changes, within the CCN, between LGG and GBM. The gene discussed is CLOCK; the disease is glioblastoma.