The protooncogene Vav1 regulates murine leukemia virus-induced T-cell leukemogenesis

Identification of Anti-tumor Cells Carrying Natural Killer (NK) Cell Antigens in Patients With Hematological Cancers

Natural killer (NK) cells, a cytotoxic lymphocyte lineage, are able to kill tumor cells in vitro and in mouse models. However, whether these cells display an anti-tumor activity in cancer patients has not been demonstrated. Here we have addressed this issue in patients with several hematological cancers. We found a population of highly activated CD56^dimCD16⁺ NK cells that have recently degranulated, evidence of killing activity, and it is absent in healthy donors. A high percentage of these cells expressed natural killer cell p46-related protein (NKp46), natural-killer group 2, member D (NKG2D) and killer inhibitory receptors (KIRs) and a low percentage expressed NKG2A and CD94. They are also characterized by a high metabolic activity and active proliferation. Notably, we found that activated NK cells from hematological cancer patients have non-NK tumor cell antigens on their surface, evidence of trogocytosis during tumor cell killing. Finally, we found that these activated NK cells are distinguished by their CD45RA⁺RO⁺ phenotype, as opposed to non-activated cells in patients or in healthy donors displaying a CD45RA⁺RO⁻ phenotype similar to naïve T cells. In summary, we show that CD45RA⁺RO⁺ cells, which resemble a unique NK population, have recognized tumor cells and degranulate in patients with hematological neoplasias.

•

Expression of both CD45 isoforms RA and RO identifies anti-leukemia NK cells.

•

Anti-leukemia NK cells proliferate, degranulate and perform trogocytosis in vivo.

•

The presence of CD45RARO population identifies hematological cancer patients.

NK cells are thought to have an intrinsic anti-tumor activity. However, the presence of anti-leukemia NK cells in patients is unknown. We present a relatively simple protocol to identify and characterize them. This is based on differential protein expression and on the fact that they gain tumor cell proteins by the process of trogocytosis. These phenotypic differences should be taken into account in analysis to identify different NK cell subpopulations. Hence, NK cells are actively recognizing tumor cells in leukemia patients; but this seems to be insufficient to eradicate disease. Future efforts should enhance the antitumor activity of this population.

Chemical metabolic inhibitors for the treatment of blood-borne cancers

Tumor cells, including leukemic cells, remodel their bioenergetic system in favor of aerobic glycolysis. This process is called "the Warburg effect" and offers an attractive pharmacological target to preferentially eliminate malignant cells. In addition, recent results show that metabolic changes can be linked to tumor immune evasion. Mouse models demonstrate the importance of this metabolic remodeling in leukemogenesis. Some leukemias, although treatable, remain incurable and resistance to chemotherapy produces an elevated percentage of relapse in most leukemia cases. Several groups have targeted the specific metabolism of leukemia cells in preclinical and clinical studies to improve the prognosis of these patients, i.e. using L-asparaginase to treat pediatric acute lymphocytic leukemia (ALL). Additional metabolic drugs that are currently being used to treat other diseases or tumors could also be exploited for leukemia, based on preclinical studies. Finally, we discuss the potential use of several metabolic drugs in combination therapies, including immunomodulatory drugs (IMiDs) or immune cell-based therapies, to increase their efficacy and reduce side effects in the treatment of hematological cancers.