“Empowering the Fight Against Ovarian Cancer: The Role of Natural Killer Cells Unveiled”

Christel Payseng
7 min readDec 19, 2023

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What are Natural Killer Cells?

NK cells, also known as natural killer cells, belong to the category of white blood cells responsible for eliminating infected and diseased cells, including cancer cells.

As a subtype of lymphocytes, akin to B-cells and T-cells, NK cells play a crucial role in halting the spread of viruses and cancer by targeting and destroying these harmful cells in their initial stages.

“Natural killer cells are our first line of defense against cancer cells,”. They scan other cells in the body and destroy any that are infected or otherwise abnormal, including tumor cells. Researchers have been trying to harness the cancer-fighting activity of NK cells that don’t carry CARs for more than 20 years, notes translational immunologist Jeffrey Miller of the University of Minnesota in Minneapolis. But upgrading them by adding CARs seems to boost their potency.

Natural killer cells (yellow) attack a cancer cell.EYE OF SCIENCE/SCIENCE SOURCE

Ovarian carcinoma is a challenging form of gynecological cancer, it requires advanced treatment therapies to combat. It has an insidious nature making it harder to detect in its early stage because patients who have it remain symptom-free until it reaches an advanced stage.

The current treatment regimen involves debulking surgery coupled with platinum and taxane-based chemotherapy. However, recurrence within three years plagues the majority of patients, prompting a dire need for innovative therapeutic approaches. Enter immunotherapy, an enticing avenue due to OC’s inherent immunogenicity, marked by T and natural killer (NK) cell infiltration within the tumor.

Studies reveal a positive correlation between the presence of tumor-infiltrating CD3+ T cells and patient survival. Further investigation indicates that CD103+ tumor-infiltrating NK cells often coexist with CD8+CD103+ T cells, hinting at their potential to improve patient outcomes. Recent discoveries underscore the relationship between increased NK cell frequency in ascites and enhanced overall survival, indicating the pivotal role of NK cells in combating OC’s progression.

Despite the susceptibility of OC to NK cell attacks in preclinical studies, tumor cells adeptly deploy strategies to stifle anti-tumor immune responses. Notably, NK cells within the tumor microenvironment display diminished cytotoxicity and an ‘exhausted’ phenotype, necessitating the exploration of strategies to bolster their efficacy for adoptive transfer in patients.

Enter allogeneic NK cell therapy, displaying safety and promise in hematological cancers. Clinical trials spotlight its success in achieving complete remission in refractory acute myeloid leukemia. Leveraging such successes has sparked intense research and exploration of NK cell therapy’s potential in OC treatment.

The potency of NK cells lies in their ability to target and destroy tumor cells without prior sensitization. This unique attribute, combined with their fine-tuned balance of activating and inhibitory receptors, fuels their cytotoxic response against neoplastic cells. Their recognition of tumor cells hinges on these receptors, triggering a cascade of events culminating in tumor cell destruction.

However, OC doesn’t relent. Its immune-suppressive tactics, including secretion of cytokines like TGF-β and IL-8, impede NK cell functionality. Additionally, OC cells adeptly downregulate activating receptors on NK cells, further hindering their anti-tumor activity.

Preclinical murine studies showcase the promise of NK cell therapy against OC. From ex vivo-expanded NK cells demonstrating cytotoxicity against autologous OC cells to the use of cytokine-induced memory-like NK cells, each avenue presents a potential breakthrough in OC treatment.

The intersection of standard OC care with NK cell functionality cannot be overlooked. Chemotherapeutic agents like paclitaxel affect NK cell-mediated killing, while surgical resection and anesthesia techniques wield their impact on NK cell counts and activity.

Moreover, the role of social support in influencing NK cell activity surfaces as a significant factor, shedding light on the multifaceted interplay between treatment outcomes and patient well-being.

Looking beyond OC, NK cell therapy’s success in hematological cancers paves the way for its exploration in solid tumors. Trials in neuroblastoma, pancreatic cancer, breast cancer, and more underscore its safety and potential efficacy without inducing graft-versus-host disease.

Yet, challenges persist. Finding the ideal ‘off-the-shelf’ NK cell product, overcoming limitations in expansion and persistence post-infusion, and navigating the intricacies of combining NK cell therapy with existing treatments remain paramount.

In conclusion, harnessing the innate power of NK cells in OC treatment holds immense promise. From unraveling their intricate interactions within the tumor microenvironment to envisioning their integration with existing therapies, the journey toward maximizing NK cell therapy’s impact on OC patients continues to unfold, offering hope in the battle against this formidable disease.

Concluding Thoughts and Future Directions

This article encapsulates the present landscape of NK cell research in combating OC and highlights early insights gleaned from NK cell therapy trials. Considerable preclinical evidence underlines the pivotal role of NK cells in OC and their potential therapeutic prowess.

However, despite promising strides, formidable challenges persist. The immune-suppressive microenvironment intrinsic to ovarian carcinoma necessitates investigation and manipulation to bolster the efficacy of NK cell therapy. Addressing the quandary of limited in vivo NK cell expansion holds the key to optimizing the anti-OC effect, a quest being explored in ongoing trials focused on IP NK cell therapy.

Moreover, efforts to develop diverse sources for an easily accessible allogeneic NK cell product are underway. Ultimately, a standardized protocol for highly potent off-the-shelf NK cell preparation is imperative to propel NK cell therapy into clinical practice. Additionally, the potential of augmenting NK cell-based immunotherapy through combination with other agents remains a promising avenue warranting exploration.

Preclinical studies outline several strategies to enhance the impact of NK cell adoptive transfer. These strategies encompass genetic modification, utilization of more efficient cytokines, construction of chimeric antigen receptor (CAR)-NK cells, coupling with checkpoint inhibitors, and amalgamation with targeted therapies. Genetic modification of NK cells to express exogenous cytokines, such as IL-15, showcases promise in cancer immunotherapy, enhancing cytotoxicity both in vitro and in vivo. Clinical trials exploring modified NK92 cells in patients with Merkel cell carcinoma epitomize this innovative approach.

Advancements mirroring the success of chimeric antigen receptor T cells (CAR-T) in T cell therapy have sparked interest in CAR-NK cells, demonstrating substantial inhibition of tumor growth and extended survival in OC xenografts. Additionally, efforts are underway to amplify antigen specificity in NK cell responses through the development of bispecific killer cell engagers (BiKEs) and trispecific killer cell engagers (TriKEs), stimulating potent NK cell responses across various cancers.

Drawing inspiration from the success of checkpoint inhibitors in other cancers, exploring their combination with NK cell adoptive therapy holds promise, though yet to be extensively studied in OC patients. The potential of these combinations, alongside standard OC therapies like gemcitabine, PARP inhibitors, and bevacizumab, awaits exploration.

Promisingly, clinical trials exploring peritoneal infusion of allogeneic NK cell adoptive transfer in OC herald a potentially more impactful avenue in ovarian cancer treatment. As preclinical evidence aligns with initial clinical trials and ongoing research focuses on enhancing NK cell adoptive transfer efficacy, a wealth of clinical evidence on its applicability against ovarian carcinoma is anticipated shortly.

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She wrote the book Scripted in Heaven, I Called Myself Cassandra, and has an upcoming book When Silence is not Golden, a book about Autism Spectrum Disorder and the New Breed of Homo Sapiens.

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Source Credits:

https://www.sciencedirect.com/science/article/pii/S0090825820302365

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