Alterations of mitochondrial biogenesis in chronic lymphocytic leukemia cells with loss of p53

Deletion of chromosome 17p with a loss of p53 is an unfavorable cytogenetic change in chronic lymphocytic leukemia (CLL) with poor clinical outcome. Since p53 affects mitochondrial function and integrity, we examined possible mitochondrial changes in CLL mice with TCL1-Tg/p53^-/- and TCL1-Tg/p53^+/+ genotypes and in primary leukemia cells from CLL patients with or without 17p-deletion. Although the expression of mitochondrial COX1, ND2, and ND6 decreased in p53^-/-CLL cells, there was an increase in mitochondrial biogenesis as evidenced by higher mitochondrial mass and mtDNA copy number associated with an elevated expression of TFAM and PGC-1α. Surprisingly, the overall mitochondrial respiratory activity and maximum reserved capacity increased in p53^-/- CLL cells. Our study suggests that leukemia cells lacking p53 seem able to maintain respiratory function by compensatory increase in mitochondrial biogenesis.