GAPVD1 and osteosarcoma: Moreover, in synchronized human U2OS osteosarcoma cells, which, in contrast to HeLa and HT1080 cells, possess a functional circadian oscillator, GAPVD1 was rhythmically associated with CSNK1D, and the strength of this interaction mirrored the binding of PER2 to CSNK1D (Figure 5E).