In a pre-print paper, scientists have shown that treatment with NMN increases the survival and anti-cancer efficacy of CAR-T cells .
The problem with immunotherapy
T cells are a central element of the adaptive immune system, and some of them can be cytotoxic: they have the ability to kill other cells. This lets us get rid of cells that are infected with pathogens, such as viruses and bacteria, along with cells that have become cancerous. However, some cancer cells have ways to greatly reduce the effectiveness of cytotoxic T-cells by causing their dysfunction and exhaustion .
Scientists have been trying to overcome this problem by genetically modifying T cells to express receptors specifically tuned to recognize various cancers. These are chimeric antigen receptors (CARs), and CAR-T cell therapies are already being used against some types of cancer.
In CAR-T cell-based immunotherapy, a bunch of T cells are procured from the patient’s blood, genetically engineered to express the relevant CAR, and injected back into the patient’s body. Unfortunately, CAR-T therapy is still mostly limited to blood cancers, where it can work marvelously, though not in all patients (CAR-T therapy with no additional treatment has a success rate of 30-40% for lasting remissions). Solid tumors have been much harder to crack because their microenvironment still quickly renders most CAR-T cells dysfunctional.
NMN keeps CAR-Ts healthy and angry
Therefore, it is extremely important to increase the resilience of CAR-T cells, and a group of scientists might have found a way to do so via a molecule that is popular in the longevity field: nicotinamide mononucleotide (NMN).
NMN is a precursor to NAD+, a co-enzyme that carries electrons for redox (reduction/oxidation) reactions. It plays an important role in mitochondrial energy production and other biological processes. The age-related decline of NAD+ levels has been linked to various diseases of aging, including cancer , while boosting NAD+ levels through NMN supplementation is known to produce multiple health benefits in mice and humans . Simply speaking, an increase in NAD+ invigorates cells, which is exactly what the authors of this new study had been looking for.
The researchers experimented on the most popular CAR-T cells that express the receptor CD19 and are used against several types of blood cancer, such as B-cell acute lymphoblastic leukemia. After being treated with a dose of NMN, the cells were co-cultured with NALM6 cells, a model of leukemia. NMN-treated T cells showed a superior rate of proliferation and remained active and cytotoxic long after the controls died.
The exhaustion of T cells that prevents them from attacking cancer cells manifests itself, in large part, in cellular senescence and increased apoptosis. In NMN-treated cells, the levels of the most popular senescence marker, ß-galactosidase, were greatly reduced compared to controls. The treated cells also showed greater telomerase activity, which is associated with reduced senescence. Apoptosis markers demonstrated a remarkable decline as well.
The treatment also changed the gene expression profile of the cells. Transcriptomic analysis showed an increased activity of proliferation-related genes and a decreased activity of senescence-inducing genes. Genes responsible for immune response got a boost as well.
NAD+ mediates the activity of sirtuins – an evolutionarily conserved family of proteins that play several important roles related to stress response and longevity. The protein Sirt1, a well-known anti-senescence and proliferation-promoting factor, was particularly upregulated by NMN. The researchers suggest that NMN benefits T cells mostly via the Sirt1 pathway.
The treatment increased the levels of pro-cytotoxic factors, including interferon-gamma (IFN-γ) and downregulated some pro-inflammatory factors such as IL-6, suggesting that NMN treatment can reduce the inflammatory response commonly triggered by CAR-T therapy.
NMN promotes survival in mice
Finally, the scientists tested NMN-CAR-T cells in a mouse model of B-cell lymphoid leukemia. While treatment with regular CAR-T cells also showed some effect, NMN-CAR-T cells caused a statistically significant additional improvement in cancer burden and median survival time.
Since NAD+ mediates many biological processes, NAD+ therapies are being actively explored for various conditions. However, scientists have encountered some delivery problems in vivo. For instance, another NAD+ precursor, nicotinamide riboside (NR), did not extend lifespan in mice in the Intervention Testing Program (ITP) trials because it failed to raise NAD+ levels. Since CAR-T therapy is based on altering and culturing cells in vitro, no such delivery issues are expected in this case; cells can be just directly treated with NMN. This also means that the experiment might be easily translatable to humans, as its design might be close to the actual therapy, and NMN is known to be very safe.
Since low fitness and survivability of T cells seem to be a major hurdle for CAR-T cell immunotherapies, especially for treating solid tumors, the results of this study, if it stands the test of a peer review, might be very influential. It also highlights, yet again, the importance of NAD+ for longevity.
 Yu, Z., Tong, S., Zhang, C., Bai, Y., An, Z., Xu, C., … & Zhong, X. (2022). Nicotinamide mononucleotide enhances the efficacy and persistence of CD19 CAR-T cells via NAD+–Sirt1 axis.
 Zhang, Z., Liu, S., Zhang, B., Qiao, L., Zhang, Y., & Zhang, Y. (2020). T cell dysfunction and exhaustion in cancer. Frontiers in cell and developmental biology, 8, 17.
 Garrido, Amanda, and Nabil Djouder. “NAD+ deficits in age-related diseases and cancer.” Trends in cancer 3, no. 8 (2017): 593-610.
 Shade, C. (2020). The Science Behind NMN–A Stable, Reliable NAD+ Activator and Anti-Aging Molecule. Integrative Medicine: A Clinician’s Journal, 19(1), 12.