Researchers develop tool to enhance NK cells against cancer

A team of researchers from the Hospital del Mar Research Institute, the Universitat Autònoma de Barcelona and the Pompeu Fabra University has developed a new tool that allows modifying these NK cells to make them immune to the tumor’s defense mechanism.

Among other functions, the NK cells (Natural Killers, a type of lymphocyte forming part of the immune system) have the capacity to detect and eliminate cancer cells. But in some cases they cannot overcome the tumor's defense mechanism and the cancer grows. Now, a study published in Nature Immunology, with the involvement of the Hospital del Mar Research Institute, the Universitat Autònoma de Barcelona and the Pompeu Fabra University, proposes a new approach to strengthen NK cells in their fight agaist tumor cells.

The study, which included the collaboration of researchers from the Karolinska Institutet in Sweden, the German firm Miltenyi, and the Dutch firm Glycostem Therapeutics, was developed under the context of a European network. It also included the involvement of researchers from the Hospital Clínic-IDIBAPS, and from the CIBER Cancer Unit (CIBERONC), the CIBER Hepatic and Digestive Disorders Unit (CIBERehd), and the CIBER Infectious Diseases Unit (CIBERinfec). To strengthen the capacity of NK lymphocytes to eliminate tumors researchers used CRISPR/Cas9, a genetic editing tool, to eliminate a gene from these cells and make them resistant to two molecules that produce tumor cells.

The goal of the study was to confirm whether modified NK cells had the capacity to overcome the negative effects of the TGF-β and Activin A molecules in preclinical models of HER2 positive breast cancer tumor cells and metastatic colorectal cancer cells. The majority of solid tumors contain an abundance of both molecules to protect themselves against attacks from the immune system. The results, both in vitro and in mice models, demonstrate that the genetically modified NK cells are capable of reaching the tumors, penetrating and destroying them, i.e., break their protective barrier. "When we compare genetically modified cells with non-modified cells, the first have a greater capacity to control the growth of in vivo tumors, both alone and when combined with other treatments and therapies being used, such as for example specific HER2 antibodies", explains Dr. Aura Muntasell, researcher from the Immunity and Infection Research Group of the Hospital del Mar Research Institute and lecturer in the Department of Cell Biology, Physiology and Immunology of the Universitat Autònoma de Barcelona.

Modifying the SMAD4 gene

To achieve these effects, researchers deactivated a specific gene, the SMAD4, involved in the signalling of TGF-β and Activin A. "To achieve this disactivation, the NK cells were transitorally exposed to the CRISPR/cas9 system, programmed with a guide so that they could head specifically towards the SMAD4, edit it and disappear", explains Marc Güell, ICREA research lecturer and head of the Synbio Lab of the Pompeu Fabra University (UPF).

"By eliminating the SMAD4 we make these cells resistant to the TGF-β's inhibition but we continue to make use of the rest of the molecule's signaling to have them acquire a greater capacity to reach tumors and penetrate them", adds Dr.. Muntasell. The study now published allows demonstrating the safety and efficiency of this approach. In collaboration with other institutions, it was also possible to verify that using it with other treatments under development that are based on the NK cells enables boosting its effect. "This strategy is also applicable to NK cells generated through different protocols, including those expressing chimeric antigen receptors (CAR), which allows recognizing specific antigens found in cancer cells. In addition, it is promising for several clinical indications, since the TGF-β suppresses the immune response in multiple types of cancer", points out Dr.. Anna Rea, first author of the article on the research conducted in her PhD thesis project at the UPF.

So far, treatments based on NK lymphocytes have been successful in hematological tumors, but have not achieved the same level of effectiveness in solid tumors. "These genetically modified NK cells offer a great treatment opportunity for patients with solid tumors that are currently resistant to immunotherapy", explains Dr. Clara Montagut, researcher at the Hospital de Mar Research Institute and head of the Digestive Oncology section in the Hospital del Mar Medical Oncology Service.

Dr. Muntasell and Dr. Montagut are precisely the two researchers leading a project that has received one of the independent research grants from the Instituto de Salud Carlos III. The grant will go towards developing a phase I clinical trial, the first of its kind, to prove the safety and tolerability of CRISP/Cas9-modified NK cells in combination with other treatments, in patients with refractory colon and rectal cancer.