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Year : 2022 | Volume
: 18
| Issue : 7 | Page : 1867-1875
Progress and prospects for use of cellular immunotherapy in pancreatic cancer
Jing Tian1, Tiankai Bai1, Zhiyong Zhang2, Xuan Zhai1, Kangmin Wang1, Xingyi Gao1, Bin Yan1
1 School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
2 School of Basic Medicine, Shandong First Medical University, Jinan, China
Correspondence Address:
Bin Yan
School of Chinese Medicine, Shandong University of Traditional Chinese Medicine, Daxue Road 4655, Changqing District, Jinan - 250355
China
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jcrt.jcrt_976_21
Pancreatic cancer (PC) is a highly malignant tumor with an increasing incidence rate in recent years. Because pancreatic cancer has an insidious onset, unknown pathophysiology, and poor prognosis, the overall survival rate of pancreatic cancer patients has not improved considerably even with extensive treatment methods such as surgery, radiation, biotherapy, and targeted therapy. Therefore, finding and developing more effective and safe treatments for pancreatic cancer is critical. Cellular immunotherapy has achieved considerable advances in the field of oncology in recent years. Technology is continuously advancing, with new breakthroughs virtually every month, and pancreatic cancer eradication is expected to improve considerably. This article examines the advance of chimeric antigen receptor NK cell immunotherapy (CAR-NK) cell immunotherapy for pancreatic cancer research, as well as research ideas for pancreatic cancer treatment.
Keywords: CAR-NK cell immunotherapy, CAR-T cell immunotherapy, pancreatic cancer, research progress
Pancreatic cancer (PC) is a cancerous tumor that affects the pancreas. Because the pathophysiology of pancreatic cancer is unknown, early detection and treatment of the disease are extremely difficult. As a result, the number of patients diagnosed with pancreatic cancer is rising over the world.[1],[2],[3],[4] According to the Global Cancer Data 2020, pancreatic cancer affects about 495,773 people worldwide in one year, with more than 46,000 individuals dying from the disease. Pancreatic cancer patients have a 5-year survival rate of fewer than 10 years.[5] Surgery is currently the main treatment approach for pancreatic cancer in its early stages. Palliative short-circuit surgery,[6] chemotherapy, and radiotherapy[7] are commonly used to treat inoperable patients, although many individuals have developed resistance to these treatments.[8] Pancreatic cancer is still one of the most lethal types of cancer.[9] Therefore, more effective treatments for pancreatic cancer are required.
Cellular immunotherapy has made substantial advances in the treatment of tumors in recent years.[10] It is a technique that involves collecting human autoimmune cells, genetically modifying and culturing them in vitro to boost specific killing activity, and then returning them to the human body to kill pathogens, cancer cells, and mutant cells in blood and tissues. For example, chimeric antigen receptor T cell immunotherapy (CAR-T) has demonstrated significant benefits in the treatment of hematologic cancers while overcoming many of the limitations of conventional therapies.[11],[12] Six CAR-T therapy medicines have been approved for marketing by the U.S. FDA according to incomplete statistics, ushering in a new era in cancer treatment. CAR-T immunotherapy is projected to enhance cancer patient survival rates when treating cancer. Although CAR-T cell immunotherapy has made significant progress in recent years, its severe neurotoxicity and cytokine storm have limited its use in clinics. Additional cell-mediated cytotoxic immunotherapies are urgently needed to overcome the disadvantages of CAR-T cell immunotherapy.
NK cells are a safe and effective alternative immunotherapy technique for T cells in clinical practice due to their distinct biological properties. Genetic engineering is also used in NK cell immunotherapy to add chimeric antibodies (CARs) to NK cells, transforming them into CAR-NK cells that detect tumor cells while activating NK cells to kill tumor cells, boosting NK cells' ability to target and kill tumor cells. Immunotherapy using CAR-T and CAR-NK cells is a promising new advance in the treatment of solid malignancies. As a result, this article provides a brief overview of the research progress of CAR-T cells and CAR-NK cells for pancreatic cancer treatment, including the basic composition of CAR-T cells and CAR-NK cells, the currently popular pancreatic cancer targets, and the major challenges and solutions they face, as well as research ideas for pancreatic cancer treatment.
> The Basic Composition of Chimeric Antigen Receptors (CARS)A tumor-associated antigen (TAA) binding region (usually derived from the ScFv segment of the monoclonal antibody-antigen binding region), an extracellular hinge region, a transmembrane region, and an intracellular signal transduction region made up the basic design of Chimeric antigen receptors (CARs). When ScFv fragments connect to tumor antigens selectively, they activate intracellular signaling regions in CAR-T or CAR-NK cells, causing them to activate, proliferate and kill tumor cells. This enables CAR-T cells or CAR-NK cells to recognize a greater number of targets than naive T cells or NK cells.[13]
> Popular Targets for Pancreatic CancerThe choice of target antigens for Chimeric antigen receptor immune cell treatment for solid tumors is important to success.[14] For the therapy of solid tumors, several target antigens have been identified. For example, a 7-year-old boy in Texas, USA, who was diagnosed with myeloid metastatic rhabdomyosarcoma and treated with HER2-CAR-T cells immunotherapy in July 2020 has been cancer-free for 19 months and no cancer cells have been detected in his body.[15] In 2020, a patient with advanced ovarian cancer who received PD-1-MESO-CAR-T cells paired with apatinib treatment at Shanghai People's Hospital, China, was in remission and lived for more than 17 months.[16] Professor Wendell Lim led a research team that produced synNotch-CAR-T, a new form of CAR-T cell that is effective against solid tumors and can completely eradicate glioblastomas of human origin in mice's brains[17]
Similarly, pancreatic cancer cells have a variety of tumor-associated antigen epitopes on their surface [Table 1] and [Table 2], which gives CAR-T or CAR-NK immunotherapy for pancreatic cancer treatment more target options.
> Challenges of CAR-T Cell Immunotherapy for Pancreatic Cancer and Strategies to Address ThemCAR-T cell immunotherapy, a strong tumor-killing cross-generational treatment, is still being studied for its efficacy and safety. CAR-T immunotherapy has numerous hurdles in the treatment of pancreatic cancer[35]: (1) Tumor microenvironment suppression. (2) Cytokine release syndrome is a condition in which cytokines are released into the body. (3) Failure of CAR-T cells. Furthermore, the majority of antigens discovered in solid tumors are tumor-associated antigens that can be expressed in other normal tissues, creating the possibility of “antigen escape” during CAR-T cell immunotherapy.
Suppression of tumor microenvironment and strategies to address it
In the stroma of solid tumors, many tumor-associated fibroblasts secrete collagen and produce dense tumor tissue, resulting in abnormally increased interstitial pressure and a physical barrier to CAR-T cell infiltration.[36] As a result, boosting CAR-T cell infiltration to reverse immune microenvironment suppression should improve the efficacy of CAR-T immunotherapy in solid tumors.[37],[38] The use of cutting-edge nanotechnology has considerably enhanced CAR-T cell targeting and increased CAR-T cell infiltration. The use of adjuvant-loaded lipid nanoparticles (LNP) in combination with medications in cancer immunotherapy has been shown to improve drug response to tumors, according to Nakamura T.[39] Drugs can reach the lesion site and have a therapeutic impact by breaking through the suppression of the tumor microenvironment using lipid nanoparticles (LNP) loaded with adjuvants. As a photosensitizer and drug carrier, Hao Y[40] created a near-infrared sensitive inorganic CuS nanoparticle. Due to the presence of folic acid on its surface, the CuS delivers the medicine into the tumor cells when injected intratumorally. The nanocarriers disintegrate under laser irradiation and release therapeutic medicines, which can be used in conjunction with photothermal therapy to ablate tumor cells and increase immunogenic cell death. These smart nanocarriers may also prevent CAR-T cells from entering tumors, allowing them to unleash their potent anti-tumor immune response and provide long-term immunological protection against tumor recurrence. Xia H[41] describes a TLR7/8 agonist-conjugated nanovaccine (TNV) that intelligently responds to the acidic environment and endosomal cathepsin precisely releases TLR7/8 agonist to activate receptor signaling at the endosomal membrane, stimulates DCs maturation, and provokes specific cellular immunity. TNV's preventive and therapeutic efficacy in mouse melanoma and colon cancer has been demonstrated in vivo. Miller IC[42] and his colleagues also introduced a genetic switch to CAR-T cells, allowing them to transport genetically engineered T cells to the tumor microenvironment precisely. After that, laser pulses were used to boost the temperature of the mouse tumor to 40–42°C, which activated the CAR-T cell gene switch and increased the expression of anti-cancer proteins. This overcomes the tumor microenvironment's inhibition and prevents tumor recurrence. To achieve rapid intracellular substance delivery and subsequent reversal of cell permeability, Kavanag HH's team[43] utilized reversible osmosis technology. In terms of manufacturing, safety, and regulation, it has potential advantages over viral vectors. Although electroporation is the most extensively used non-viral form of cell engineering, it can cause damage to cells. Lysis, on the other hand, is the least harmful to human T cells. Castellari M[44],[45] developed a switchable immune receptor Sortases CAR (Srt.bbz), which can connect to several tumor antigens and allow CAR-T cells to switch to recognize their target antigens, and preliminary testing has demonstrated that Srt.bbz T cells can lyse tumor cells.
In addition, Y-mAbs has developed naxitamab, a humanized monoclonal antibody that binds to GD2 antigen on the tumor surface and activates the complement system in the immune system, triggering an antibody-mediated cytotoxic response and activating the complement system in the immune system, preclinical data shows that it aids CAR-T reversing immunosuppression of the cellular tumor microenvironment. Researchers at City of Hope in the United States have developed a new form of B cell activating factor receptor (BAFF-R) CAR-T cells that target the CD19 antigen and has a better ability to bind to tumor cells by replacing the CD19 target with the B cell activating factor receptor (BAFF-R). The development of these technologies enhances the milieu for CAR-T therapy in the treatment of malignancies, and it may also improve pancreatic cancer treatment.
Cytokine release syndrome (CRS) and strategies to address it
The excessive release of cytokines including IL-6 and IL-10 at the moment of T cell activation following CAR-T treatment causes cytokine release syndrome (CRS).[46],[47] CAR-T cell treatments that target CD19, BCMA, and CD22 have all resulted in severe cytokine crises so far.[48] This necessitates inserting a “control gene” into the CAR-T gene, which effectively prevents cytokine storms. It's still a big problem to avoid cytokine storms after CAR-T treatment while pancreatic cancer treatment is still in preclinical or early clinical trials.
CAR-T cell failure and strategies to address it
CAR-T has achieved several advancements in hematological cancers, but solid tumors have long been a barrier. The main cause of CAR-T failure is non-antigen-dependent activation, which has become the main optimization route for CAR-T cells to combat pancreatic cancer. Some researchers, for example, have developed the STAR double-chain chimeric receptor, which integrates the antigen recognition and TCR activation pathways of CAR-T [Figure 1] and has higher antigen sensitivity and improved T cell persistence than CAR-T cells, making it a promising treatment for pancreatic cancer.[49] The Weberew S team[50] discovered that epigenetic modification can restore the function of failing CAR-T cells. Proline dehydrogenase 2 (PRODH2) has also been found to improve the therapeutic efficacy of CAR-T cells in a variety of animal cancer models.[51] They used a dead-guide RNA (dgRNA)-based CRISPR activation screen in primary CD8+ T cells to find a CAR-T engineering gain-of-function target. PRODH2 engineering improved the antitumor metabolism and immunological function of CAR-T cells, and PRODH2 was a target for improving CAR-T cell efficacy, according to the researchers.
Antigen escape and strategies to address it
One of the most successful approaches to address antigen escape is to investigate pancreatic cancer tumor surface-specific antigens. However, all of the antigens discovered so far are tumor-associated antigens. As a result, researchers expect to lessen the “off-target” effect by developing dual-target CAR-T cells. In a phase, I trial in patients with relapsed/refractory pre-acute B-lymphoblastic leukemia (B-ALL), Dai H[52]et al. demonstrated that bispecific CD19/CD22 CAR-T cells can have strong cytolytic activity against target cells and induce relapsed/refractory B-ALL in adult patients with a remission effect. Antigen escape can also be caused by low antigen expression in solid tumors, and how to tackle this problem will be a future focus of CAR-T therapy.
> Challenges of CAR-NK Cell Immunotherapy for Pancreatic CancerCAR-NK cells offer distinct advantages over CAR-T cells, although they still face significant obstacles. Improvements in NK cell proliferation, activation of NK cell toxicity, and the best technique to rebuild NK cells are among the issues.
In vitro expansion of NK cells is the first hurdle for CAR-NK cell immunotherapy
Because a single donor's NK cells are insufficient for treatment, it is critical to figure out how to multiply NK cells in vast quantities. Although it has been discovered that irradiation improves NK cell multiplication, the lack of donor cell numbers remains a hurdle.[53] To avoid the development of GVHD (graft-versus-host disease), T cells must be totally eliminated when treating tumors with CAR-NK cells. As a result, getting enough NK cells remains a challenge.
CAR-NK cell construction is the second hurdle for CAR-NK cell immunotherapy
Retroviruses and lentiviruses have been employed to transfect CARs in the past. Although retroviral vectors have a high transfection efficiency, they can produce insertional mutations, cancer, and other side effects. Using lentiviral vectors, on the other hand, despite the low occurrence of insertional mutations, the efficacy of transfecting NK cells was similarly reduced. As a result, increasing the efficiency of CAR transfection provides another avenue for tumor therapy.
> Innovative Combination TherapyImmune cell treatments' therapeutic potential can be boosted by combining immunosuppressive medications, targeted medicines, or other techniques, in addition to optimizing CARs themselves.
Combined therapy with CRISPR/Cas9 gene technology
CRISPR-associated nuclease9 (CRISPR/Cas9) technology, a bacterial and archaeal-acquired immune system, has provided a new tool for precise genome editing. It was a simple and flexible genome editing method that targeted practically any genomic locus by using only a single nuclease protein in conjunction with two short RNA as a site-specific endonuclease. CRISPR/Cas9 technology as a genetic editing tool in combination with CAR-T cell treatment has been shown in studies to improve the efficiency and safety of CAR-T cells. CRISPR/Cas9 technology was used by Zhang S[54] to knock down the GPR54 or ERK5 gene in CAR-T cells, which improved the anti-tumor response of CAR-T cells to PSMA+ and CD19+ tumor cells while avoiding T cells depletion. Alishah K[55] used the CRISPR/Cas9 system to knock out the TGFβRII gene in T cells, allowing CAR-T cells to proliferate and inhibit tumors more effectively. CRISPR/Cas9 technology has also been used in CAR-NK cell therapy to improve NK cell anti-tumor function. CRISPR/Cas9 technology was employed by May Daher et colleagues[56] to remove the CISH gene in CAR-NK cells, which improved their metabolic capacity and anti-tumor effectiveness. CRISPR/Cas9 technology was utilized by one team[57] to disrupt the CD38 gene during CAR-NK cells expansion and knocking down the CD38 gene NK cells reduced cell self-mutilation and improved the treatment of acute myeloid leukemia (AML). All of these findings point to CRISPR/Cas9 gene editing technology being able to improve the efficacy of cellular immunotherapy in cancer treatment.
Combined therapy with immune checkpoint inhibitors
Scholars focused solely on improving T-cell activation in the early days of pancreatic cancer treatment. Researchers didn't know that T-cell activation was followed by activation of the suppressor t-cell pathway until the late 1980s. Immune checkpoint inhibitors, such as monoclonal antibody inhibitors, stimulate systemic immunity and boost T-cell activity by blocking T-cell inhibitory signaling pathways. Immune checkpoint inhibitors can thereby slow tumor progression and possibly eliminate tumors.[58],[59],[60],[61],[62],[63],[64],[65],[66],[67] Similarly, checkpoint inhibitors can enhance CAR-T cells' proliferative potential by blocking the inhibitory signaling pathway. As a result, they work together to prevent antigen escape and improve the targeting and tumor-killing abilities of CAR-T cells. To treat pancreatic cancer, Ching Y[68] employed chimeric antigen receptor T cells in combination with immune checkpoint inhibitors PD-1/PD-L1. In vitro tests revealed that 80 percent of tumor cells overexpressing PD-L1 could be detected and eliminated [Figure 2]. Chong EA[69] also described a case of a patient with refractory diffuse B large cell lymphoma who was unresponsive after therapy with CD19-CAR-T cells, but whose symptoms were reduced after co-treatment with pembrolizumab, which increased CAR-T cells activity and improved CAR-T cells activity. CAR-T cells paired with immune checkpoint inhibitors may be successful in treating solid tumors, according to the American Cancer Society in 2019. Grosser[70] further stated that using immune checkpoint inhibitors alone to treat pancreatic cancer is currently ineffective. These findings give a theoretical foundation for using CAR-T cells in combination with checkpoint inhibitors. In tumor patients, NK cells have been found to exhibit the inhibitory checkpoint PD-1, according to recent research. As a result, checkpoint inhibitors may improve the effectiveness of CAR-NK cells against PD-L1-positive malignancies.[71]
Combined therapy with oncolytic viruses
Oncolytic viruses (OVs) selectively infect tumor cells and replicate in large numbers, eventually lysing the cells and expanding the invasion space of immune cells in tumor tissues,[72],[73] suggesting that OVs combined with CAR-T or CAR-NK therapy could break through the immune microenvironment of pancreatic cancer.[72],[73] Transgenic OVs can release cellular immune components, activate the body's immune system, and target and kill tumor cells after penetrating tumor cells. Reoviridae, HSV virus, and tumor lysing adenovirus can all be utilized as vectors to deliver encoded gene snippets to tumor cells. They can lyse the extracellular matrix of pancreatic cancer cells in this way, improving the immunological microenvironment of pancreatic cancer, increasing tumor cell exposure, and inhibiting pancreatic cancer metastasis. OVs have a wide host range, similarity with human genes, and no mutation when introduced into the host, therefore it may be employed as a viral vector to create CAR-T or CAR-NK cells, compared to other viral vectors. Following that, a group of researchers discovered that OV19s and CD19-CAR-T cells had a remarkable synergistic impact, killing cancer cells in large numbers. In a glioblastoma (GBM) mouse model, Ma R[74] discovered that combining OVs expressing IL15/IL15Rα complexes with EGFR-CAR-NK cells increased overall survival and dramatically suppressed tumor development compared to monotherapy. As a result, using mildly pathogenic viruses could improve the efficiency of cellular immunotherapy for pancreatic cancer while also providing new research ideas.
Combined therapy with targeted drugs
Many molecularly targeted therapeutic drugs have first shown anti-pancreatic cancer properties, thanks to the rapid development of contemporary immunology and molecular biology. Epidermal growth factor (EGFR) receptor-targeting medications, vascular endothelial growth factor targeting drugs, anti-angiogenic matrix metalloproteinase inhibitors (MMPIs), and other pharmaceuticals are commonly used. In pancreatic cancer treatment, cetuximab inhibits EGFR phosphorylation, decreases VEGF production, and prevents neovascularization, increasing the toxicity of CAR-T or CAR-NK cells.
Combined therapy with antineoplastic drugs
By modulating cytokines or down-regulating the PD-1/PDL1 pathway, some standard anti-tumor medications [Table 3] can suppress tumor cell growth and migration. When these medications are used with cellular immunotherapy, immune cells are more likely to connect to specific antigens or related antigens on the surface of tumor cells, resulting in a synergistic effect with immune cells in the treatment of cancer.[75],[76]
> ConclusionTogether, with the advancement of modern technology and the efforts of researchers from numerous countries, there is a great deal of optimism that cancer can be defeated. At the moment, it's difficult to entirely eradicate malignancies with a single treatment. Combination immunotherapy for cancers will be the main research focus in the future, although traditional methods will continue to play an essential part in the treatment process. Genetic engineering, which can repair and modify mutations or gene deletions and is a milestone in the radical cure or prevention of cancer, has many advantages in addition to immunotherapy. This strategy, however, still has a number of flaws. Although gene therapy is theoretically conceivable, few gene therapy approaches have been used in clinical practice, and the majority of them are still in the research and animal testing stages. In the United States, a patient died after receiving gene therapy.
The medicine has major repercussions since it entered the body without replacing or deleting the disease-causing gene. Furthermore, numerous teams have made substantial advances in the use of TCR-T for cancer treatment, implying that TCR-T can identify a broader spectrum of potential tumor-specific antigens or improve tumor-killing effects.[82],[83] Clinical trials using TCR-T to treat various types of cancer are now being conducted by companies such as Adaptimmune, Immunocore and TCR2 Therapeutics. With the success of CAR-T cell therapy and the huge potential of CAR-NK cell therapy, scientists are looking into the ability of mononuclear macrophages (MPS) to phagocytose exogenous microorganisms once more. CAR-Macrophages (CAR- M) have been shown to have considerable benefits in the treatment of solid malignancies in preliminary investigations. It solves the problem of CAR-T cells invading the tumor microenvironment and offers a lot of research potential. The FDA has approved two clinical trials based on the CAR-M approach, providing yet another research avenue for pancreatic cancer treatment. The eradication of solid tumors is seen to be inevitable as technology improves.
Financial support and sponsorship
Shandong Provincial Medical and Health Science and Technology Development Program (No.:202002050626), the Subproject of Major New Drug Innovation and Technology Special Project of the Ministry of Health of China (2014ZX09509001001).
Conflicts of interest
There are no conflicts of interest.
> References
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