Natural Killer (NK) cell-mediated effector functions significantly contribute to anti-tumor activity of tumor targeting monoclonal antibodies (mAbs): indeed, CD16 (FcgammaRIIIa) aggregation by means of opsonised targets not only triggers tumor cell killing but may also favour the development of long lasting IFN-gamma-dependent anti-tumor T cell responses. Notably, memory or adaptive NK cells are an epigenetically-shaped long-living CD94/NKG2C+FcepsilonRIgamma- NK subpopulation identified in HCMV seropositive individuals, endowed with the enhanced ability to mediate CD16-dependent cytotoxicity and IFN-gamma production in response to opsonised target stimulation. Our recent data demonstrate the unique capability of anti-CD20 therapeutic mAbs to drive the selective in vitro expansion of memory NK cells, which maintain the phenotypic and functional signature of their freshly isolated counterpart.
Our project is aimed at studying the mechanistic basis of memory NK cell anti-tumor activity, that will allow their exploitation in adoptive therapy strategies to gain and sustain anti-tumor responses in therapeutic mAb-treated patients.
Main objectives:
1. To characterize the in vivo dynamics of memory NK cells in patients affected by B-cell chronic lymphocytic leukemia (CLL) and diffuse large B-cell lymphoma (DLBCL), before and after anti-CD20 mAb-based regimens.
2. To characterize the molecular basis of tumor cell recognition, activation, and tissue homing profile of memory NK cells, as well as to set up GMP-compliant conditions for memory NK cell expansion.
3. To explore the ability of memory NK cells to favour dendritic cells (DCs) maturation finalysed to mAb-driven antitumor "vaccinal effect".
Despite the unprecedented success of rituximab anti-CD20 mAb, a proportion of patients still fails to respond to or more commonly relapses, after receiving rituximab-containing chemoimmunotherapy, and the promotion of an endogenous long-lasting anti-tumor immune response in mAb-treated patients is becoming a major goal for improving the efficacy of mAb-based therapies.
The in-depth ex vivo and in vitro characterization of the phenotypic and functional profile of memory NK cells in therapeutic mAb-treated patients has several major implications: 1. to elucidate a novel mechanism of NK cell memory generation driven by CD16 (FcgammaRIIIa) in a therapeutic setting; 2. to provide a mechanistic explanation for the ability of NK cells to support the generation of an anti-tumor vaccinal effect in response to mAb treatment; 3. to provide an experimental framework for the rational design of combination therapy protocols aimed at optimising the efficacy of therapeutic mAb, and at enhancing the anti-tumor activity of NK cells.
We strongly believe that the results of this research project will uncover previously unrecognized mechanisms of NK cell plasticity and provide information with a strong translational potential. The characterization of memory NK cells ability to affect DC maturation and functions will be instrumental for the design of anti-tumor mAb-based therapies able to more effectively promote the development of long-term adaptive responses in cancer patients. Further, taking into account that the poor in vivo survival and the lack of specificity of NK cells have limited their use in adoptive therapy strategies, the definition of the phenotypic and functional profile of a long-lived NK cell population with powerful anti-cancer skills, and the GMP-compliant adaptation of the procedure for their in vitro expansion, will be instrumental for the better exploitment of NK cells for the ultimate benefit of treating cancer patients.