Autologous natural killer cells as a promising immunotherapy for locally advanced colon adenocarcinoma: Three years follow‐up of resectable case

Abstract Background Over the last decade, a new modality of immunotherapy has been announced, with the expectation of better long‐term clinical outcomes and disease‐free survival after the definitive surgical treatment of colon cancer. Natural killer (NK) cells as part of cellular therapy in immunotherapy have the potential effect as an adjuvant therapy for locally advanced and metastasized colorectal adenocarcinoma. We would evaluate the clinical outcome of autologous NK cell therapy for resectable colon cancer. Case A 64‐year‐old woman presented with a transverse colon tumor‐related partial intestinal obstruction and a history of bloody diarrhea. A transverse colectomy has been done, and the pathology report reported adenocarcinoma of the transverse colon and positive lymph node involvement (TNM stage III). The patient had R0 resection status. A PET scan was done 6 months later, with positive lymph node glucose uptake at mesocolic. NK cell therapy was administered for 2 cycles with a 3‐month interval, and PET scan follow‐up was done 3 years after resection; no more glucose uptake was found, and the patients tolerated the therapy well with no immune‐related adverse effects reported. Conclusion As a new modality in immunotherapy strategies for locally advanced colon adenocarcinoma, particularly in cases unsuitable for standard chemotherapeutic treatment, autologous NK cells have a promising effect and are feasible and well tolerated in our clinical practice.


| INTRODUCTION
The potential of immunotherapies based on natural killer (NK) cell involvement was first discovered in the hematological setting. However, this discovery has spurred the construction of many immunological responses that can also be used against solid tumors, such as colorectal cancer (CRC). In point of fact, despite efforts toward cancer prevention in the form of screening programs, surgical procedures, and chemotherapy, CRC remains one of the malignancies with the highest mortality rate.
In recent years, there has been an increase in interest in using the NK anti-tumor capacity as a novel immunotherapeutic strategy, and various clinical trials based on NK cell infusion have been designed or are being planned. 1 Some of these studies are currently underway, such as a phase I study in which the effectiveness of allogeneic, in vivo activated NK cells is assessed in several advanced solid tumors, including CRC, either alone or in combination with monoclonal antibodies (trastuzumab or cetuximab). 1,2 Drug development has exploded in response to immunotherapy's potential to induce long-lasting remissions in advanced diseases, with a particular focus on creative combinatorial immunotherapeutic approaches. NK cells as part of cellular therapy in immunotherapy have the potential as an adjuvant therapy for locally progressed and metastatic colorectal adenocarcinoma. 3 With the creation of numerous immune cells that can be used as therapeutic agents, cancer immunotherapy has firmly established itself as a new benchmark in cancer treatment. NK cells are innate immune cells with strong cytolytic activity against tumors that also serve as immune system regulators. Immune stimulants including cytokines and antibodies, as well as adoptive transfer of activated NK cells generated ex vivo, can improve the effectiveness of NK cell-mediated immunotherapy. 2,3 Particularly in our developing country with many limitations on advanced cancer treatment support from the government health insurance and private insurance, the routine guideline that we use is adjuvant chemotherapy for locally advanced CRC. As a brand-new cellular therapy, usually we use these as additional treatments after standard chemotherapy or a combination of them. We lack supporting data in our local cases, which can be used as an option for locally advanced CRC. Although many prospective cohort studies reported the effectiveness of this cellular therapy on reduced the cancer pro- From the family history, the patient has no history of related cancer in her first or second-degree relatives. No history of tumors in other organs related to her family. Preoperative carcino embryonic antigen (CEA) level was 1.5 ng/mL (<3.0 ng/mL), and the patient has no cardiopulmonary comorbidity. The pre-operative laboratory examination was within the normal limit. The hemoglobin level was 11.7 g/dL (12.0-15.6 g/dL), the white blood count was 10 300/uL (4500-110 000/uL), the platelet count was 146 000 /uL (150 000-450 000 /uL), the urea level was 45 mg/dL (<50 mg/dL), the creatinine level was 0.8 mg/dL (0.6-1.1 mg/dL), and the aspar-  In this preliminary study, we reported the effectiveness of NK cells as monotherapy (immunotherapy) for this single case of locally advanced colon cancer. As an option for our routine use of chemotherapy agents, or in combination with those agents as adjuvant treatment, the clinical efficacy of the NK cell therapy could be tolerated well. Although this kind of therapy is not routinely used in our clinical practice (especially in our developing country), according to the promising effect, the NK cell therapy would be our choice in the future. For the next step, the immune-related adverse effect should be evaluated over a long period of time.
Immunotherapy for solid cancers, including CRC, could be administered as monotherapy or in combination with conventional chemotherapeutic agents (5-fluorouracil, leucovorin, oxaliplatin, irrinotecan, and such targeted therapies). Many studies have reported that the F I G U R E 2 Positron emission tomography-scan evaluation after natural killer cells treatment, on the axial view we found no more fluoro-deoxy-glucose uptake in the locoregional metastasis and no additional uptake in the intra-abdominal cavity. combination therapy of chemo and immunotherapy gives a better clinical outcome, DFS, and OS. 6 In this case study, the patient received only cellular therapy because she was unsuitable for adjuvant chemotherapy.
Immune-related adverse effects during immunotherapy administration are one of many issues that should be discussed; it would be too early to state that NK cell therapy has no immune-related adverse effects according to this report. We should evaluate the OS, including the quality of life, of the patients receiving this immunotherapy. 7 The landscape of oncological treatment has undergone a paradigm shift thanks to cancer immunotherapy. It has become obvious that NK cells provide various advantages that can be utilized for immunotherapy, with potentially fewer side effects, in contrast to most research, which concentrated on saving T-cells from depletion in an effort to unleash tumor-specific immune responses. 3,6 NK cell immunotherapy as a stand-alone therapy or in conjunction with chemotherapy would be advantageous options in this situation because chemotherapy causes resistance in many types of cancer, including CRC. 8 This favorable response of NK cell therapy on resectable cancer has been evaluated in a case with R0 resection status and a tolerable adverse effect. We should take into consideration evaluating the other cases with R1 or R2 resection types to see if they would have the same response as this ideal R0 status. The other consideration against the role of NK cells as an immunotherapy for solid cancers, such as CRC, is the possibility of overcoming resistance to this cellular therapy. 11 Long-term follow-up and further study should be done to support the wide recommendation of cellular therapy, particularly for CRC. As a clinician, what we should do is conduct closed follow-up and clinical evaluation during this immunotherapy treatment.
Because it is known that the immune system has a role in the development and spread of CRC, certain cell subsets, such as T cells, NK cells, and natural killer T (NKT) cells, are relevant study targets for immunotherapy and clinical biomarker research. The function of systemic immune profiles in the development of tumors has been a mystery up to this point. Krijgsman et al reported that the peripheral circulating level of the NK cell is associated with these kinds of progression and clinical outcomes. 12 Actually, that was our limitation, we hope that in the future, our center can perform this advanced examination not only evaluating the clinical response after cellular therapy administration.
The other issue to be discussed about this cellular therapy is we do not know yet how many times this therapy could be given to the patient, particularly when we found unresectable cases and already have no response for adjuvant chemotherapy before. In the future, we should evaluate the effectiveness of this cellular therapy in these selected cases, in our opinion, when there is a supportive facility and no comorbidity presence, the cellular therapy should have a recognition in our clinical judgment when the other therapy modalities did not give favorable response.

| CONCLUSION
Autologous NK cells could have a promising effect, be feasible, and well tolerated as one of the multimodal treatment options in our clinical practice as a new modality in immunotherapy strategies for locally advanced colon adenocarcinoma, particularly in cases unsuitable for standard chemotherapeutic treatment.

AUTHOR CONTRIBUTIONS
Budhi Ida Bagus has contributed on conception, design, interpretation of data and responsible for the content of this manuscript.

ACKNOWLEDGMENTS
The author declares there is no conflict of interest to be reported.

CONFLICT OF INTEREST STATEMENT
The authors have stated explicitly that there are no conflicts of interest in connection with this article.

DATA AVAILABILITY STATEMENT
Data availability statement is not applicable.

ETHICS STATEMENT
This case study has already been approved by Health Research Ethic Committee of Moewardi General Hospital, Surakarta, Indonesia. Ethical clearance number: 127/III/HREC/2021.

INFORMED CONSENT
The patient has already been informed about the purpose of this case study and get patient permission on using of the clinical material such as clinical finding during operation, radiological exam for the publication. The patient already signed the written informed consent for the usage of the information and clinical images for publication.