HIF1A and plasma cell myeloma: As shown in Fig. 1a (middle panel), by contrast to hypoxic conditions, in anoxia metformin was not able to attenuate the HIF-1 alpha accumulation and in consequence the HIF-1 transcriptional response, what indirectly suggests that complex I impairment and subsequent oxygen shift from mitochondria to cytosol may play a role in HIF-1 signaling inhibition in metformin treated hypoxic myeloma cells.