Cell Therapies For Cancer - Introduction to CAR-T / CIK / TIL

🧬 Cancer Immunotherapy

Applied Technology：

• CIK Therapy (Cytokine-Induced Killer cells)
• TIL Therapy (Tumor-Infiltrating Lymphocytes)
• CAR-T Cell Therapy (Chimeric Antigen Receptor T cells)

• Cancers Treated:

  • Blood cancers (e.g., leukemia, lymphoma) — CAR-T is most advanced

  • Solid tumors (e.g., melanoma, lung cancer, gastric cancer) — TIL and CIK in clinical use

• Mechanism: Enhances T cells' ability to recognize and kill cancer cells through targeted immune activation

CAR-T Therapy

Chimeric antigen receptor T-cell therapy (CAR-T cell therapy) is an advanced gene-modified immunotherapy. Below is an overview of its mechanism, manufacturing process, approved products, main clinical indications, efficacy and risks, and development challenges with future trends.

1. Definition and Mechanism of Action

CAR-T cells are patient-derived T cells that have been genetically engineered to express a chimeric antigen receptor (CAR) on their surface. This receptor enables them to directly recognize and bind a specific antigen on tumor cells. Upon antigen binding, CAR-T cells become activated, proliferate, and release cytotoxic molecules that selectively kill antigen-bearing cancer cells, while also amplifying the overall immune response .

2. Manufacturing and Treatment Process

1. Leukapheresis: Collection of peripheral blood mononuclear cells from the patient to isolate T cells.

2. Genetic Transduction: Introduction of the CAR gene into T cells using viral vectors (typically retroviral or lentiviral).

3. Expansion: Ex vivo proliferation of the engineered CAR-T cells under controlled culture conditions, which usually takes several weeks.

4. Lymphodepletion: Administration of lymphodepleting chemotherapy to the patient to create "space" for the infused CAR-T cells.

5. Infusion: Return of the expanded CAR-T cells to the patient, where they seek out and destroy tumor cells .

3. Approved CAR-T Products

• Tisagenlecleucel (Kymriah): Indicated for relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) and large B cell lymphoma.

• Axicabtagene ciloleucel (Yescarta): Approved for relapsed/refractory large B cell lymphoma, follicular lymphoma, and other B cell malignancies.

• Lisocabtagene maraleucel (Breyanzi): For various relapsed/refractory non-Hodgkin lymphomas, including diffuse large B cell lymphoma and follicular lymphoma .

• Idecabtagene vicleucel (Abecma) and Ciltacabtagene autoleucel (Carvykti): Targeting BCMA for multiple myeloma.

• Tecartus: Indicated for relapsed/refractory mantle cell lymphoma.

In June 2025, the U.S. FDA removed the REMS (Risk Evaluation and Mitigation Strategy) requirements for these CAR-T therapies, retaining only enhanced labeling and warnings to streamline clinical use and broaden patient access.

4. Main Clinical Indications

• Hematologic Malignancies:

  • B cell acute lymphoblastic leukemia (B-ALL)

  • Diffuse large B cell lymphoma (DLBCL)

  • Follicular lymphoma, mantle cell lymphoma (MCL)

  • Multiple myeloma (BCMA-targeted CAR-T) .

• Solid Tumors (Clinical Trials): CRISPR-edited CAR-T cells targeting breast, colorectal, and ovarian cancers have shown high efficacy and reduced toxicity in animal models and are expected to enter human trials within five years .

5. Efficacy and Risks

• Efficacy: Complete remission rates of 40–90% in relapsed/refractory hematologic cancers, with many patients achieving durable remissions.

• Major Risks:

  • Cytokine Release Syndrome (CRS): Manifests as high fever, hypotension, and organ dysfunction; requires prompt supportive care.

  • Neurotoxicity: Includes confusion, aphasia, and seizures; generally reversible.

  • B cell Aplasia: If targeting CD19, normal B cells may be depleted, necessitating immunoglobulin replacement.

Careful monitoring and management of these toxicities are essential to maximize safety and efficacy .

6. Challenges and Future Trends

1. Solid Tumor Barriers: Immunosuppressive tumor microenvironment, antigen heterogeneity, and poor T cell infiltration hamper efficacy in solid tumors.

2. Antigen Escape: Tumor cells may downregulate or mutate target antigens; bispecific or switchable CAR designs are in development to mitigate this.

3. Allogeneic ("Off-the-Shelf") CAR-T: Using healthy donor T cells to create a universal CAR-T product could reduce costs and accelerate availability.

4. Smart Control Systems: Inducible expression systems, genetic circuits, or small-molecule switches aim to fine-tune CAR-T activity and persistence, improving safety and tolerability.

With advances in gene editing, nanotechnology, and synthetic biology, CAR-T cell therapy is poised to overcome current limitations, broaden its indications, and become a standard option for a wider patient population.

CIK Therapy

Cytokine-Induced Killer (CIK) cell therapy is an ex vivo–induced and expanded immunotherapy in which a patient's (or donor's) mononuclear cells are cultured with cytokines to generate highly cytotoxic CD3⁺CD56⁺ cells, then reinfused to enhance antitumor immunity. Below is an overview of its definition and history, mechanism of action, manufacturing process, clinical applications, efficacy and safety, and challenges with future directions.

1. Definition & History

CIK cells were first described by Schmidt-Wolf et al. in 1991 and entered early cancer trials in 1999. They exhibit characteristics of both T cells and natural killer (NK) cells, combining potent, non–MHC-restricted cytotoxicity with relatively low toxicity.

2. Mechanism of Action

Peripheral blood or cord blood mononuclear cells are cultured sequentially with interferon-γ, anti-CD3 antibody, IL-1, and IL-2, yielding a large population of CD3⁺CD56⁺ "CIK" cells. These cells recognize and lyse a broad spectrum of tumor targets—including lines resistant to conventional NK or LAK cells—primarily via the perforin/granzyme pathway.

3. Manufacturing Process

1. Cell Collection: Harvest peripheral blood mononuclear cells (PBMCs) from patient or healthy donor (or cord blood).

2. Cytokine Induction: Culture PBMCs with IFN-γ for 24 hours, then add anti-CD3 antibody and IL-2, continuing culture for 14–21 days to expand CD3⁺CD56⁺ cells.

3. Quality Control: Assess phenotype (CD3⁺CD56⁺ percentage), sterility (bacterial/mycoplasma), and endotoxin levels.

4. Infusion: Administer the qualified CIK cell product back to the patient, optionally in combination with chemotherapy, radiotherapy, or targeted agents.

4. Clinical Applications

• Solid Tumors: Adjuvant CIK therapy in colorectal, hepatocellular, pancreatic, and ovarian cancers has shown reduced recurrence and improved survival in multiple trials.

• Hematologic Malignancies: In acute leukemia, lymphoma, and multiple myeloma studies, CIK cells—often combined with other immunotherapies or chemotherapy—have significantly prolonged progression-free and overall survival.

• Combination Strategies: Co-administration with dendritic cells (DCs), PD-1/PD-L1 inhibitors, or chemotherapeutics can further enhance cytotoxicity and clinical benefit.

5. Efficacy & Safety

A systematic review covering 10,225 patients (1999–2019) reported that CIK therapy significantly improved median progression-free survival (mPFS), median overall survival (mOS), and overall response rate (ORR). Adverse events were generally mild—fever and fatigue—with very low rates of severe toxicity .

6. Challenges & Future Directions

1. Efficacy Variability: Yield and functionality of CIK cells vary across centers and patients; standardized manufacturing and potency assays are needed.

2. Immunosuppressive Tumor Microenvironment: Solid tumors often inhibit CIK function; future work will focus on enhancing tumor infiltration and resistance to suppression.

3. Combination Immunotherapies: Synergies with checkpoint inhibitors, CAR-T cells, or nano-formulated drugs are under investigation to broaden efficacy.

4. "Off-the-Shelf" CIK Products: Allogeneic or gene-edited CIK cell banks may lower costs and improve accessibility.

With ongoing process optimization, combinatorial regimens, and advances in genetic engineering, CIK therapy is poised to become a more universally applicable, safe, and effective cancer immunotherapy.

TIL Cell Therapy

Tumor-Infiltrating Lymphocyte (TIL) Therapy is a form of autologous cell-based immunotherapy in which a patient's own lymphocytes, isolated from their tumor microenvironment, are expanded ex vivo and reinfused to attack the tumor. Below is an overview of its definition and history, mechanism of action, manufacturing process, clinical applications, efficacy and safety, and challenges with future directions.

1. Definition & History

TIL therapy was first described by Rosenberg et al. in 1988. Tumor-infiltrating lymphocytes are T cells that have naturally migrated into the tumor tissue and therefore reflect the patient's endogenous anti-tumor immune response. Early studies demonstrated that TILs, when isolated from tumor fragments and expanded with high-dose interleukin-2 (IL-2) in vitro, could be activated to kill tumor cells with high potency.

2. Mechanism of Action

Once activated and expanded with IL-2, TILs recognize tumor cells in a non–non-MHC-restricted manner, releasing perforin and granzymes—and secreting cytokines such as interferon-γ—to induce tumor cell apoptosis. They also modulate the tumor microenvironment by secreting additional cytokines, further enhancing anti-tumor immunity.

3. Manufacturing Process

1. Tumor Harvesting: Surgical resection or biopsy is used to obtain a tumor fragment.

2. Initial Outgrowth: The fragment is minced or enzymatically digested, and lymphocytes are cultured in media containing high-dose IL-2.

3. Rapid Expansion (REP): Anti-CD3 antibody and feeder cells (e.g., irradiated PBMCs) are added to drive a 10- to 100-fold expansion over 14–21 days.

4. Quality Control & Formulation: Expanded TILs are tested for phenotype (e.g., CD3⁺, CD8⁺ frequency), cytotoxic potency, sterility, and endotoxin levels.

5. Lymphodepletion & Infusion: The patient receives a lymphodepleting chemotherapy regimen, then is infused intravenously with the TIL product, followed by supportive high-dose IL-2 to promote in vivo persistence and expansion.

4. Clinical Applications

• Melanoma: In February 2024, the FDA approved Lifileucel (brand name Amtagvi) for patients with unresectable or metastatic melanoma who progressed after PD-1 inhibitors (and, if BRAF-mutant, after BRAF/MEK inhibitors). This is the first approved TIL cell therapy for a solid tumor.

• Other Solid Tumors: Ongoing trials are evaluating TIL therapy in cervical cancer, non-small-cell lung cancer, colorectal cancer, and others, with early data showing objective responses and durable disease control in some patients.

5. Efficacy & Safety

In advanced melanoma patients treated with Lifileucel, complete response rates are approximately 20–25% and overall response rates 30–40%, with many responders maintaining benefits beyond six months. Adverse events are primarily related to the preparative lymphodepletion (e.g., cytopenias) and high-dose IL-2 support (e.g., fevers, hypotension, transient renal impairment) and require administration in specialized centers with cell therapy expertise.

6. Challenges & Future Directions

1. Complex, Costly Manufacturing: The manual, multi-step process can cost hundreds of thousands of dollars per patient.

2. Immunosuppressive Tumor Microenvironment: Factors such as TGF-β, IL-10, regulatory T cells, and myeloid-derived suppressor cells can inhibit TIL function. Strategies under investigation include genetic engineering of TILs or combining with checkpoint inhibitors to overcome suppression.

3. Automation & Standardization: Development of closed-system bioreactors and AI-driven monitoring aims to increase yield, reduce contamination risk, and hasten product release.

4. Allogeneic ("Off-the-Shelf") TIL Banks: Research is exploring the use of healthy donor or gene-edited universal TIL lines to shorten manufacturing time, lower cost, and minimize batch-to-batch variability.

With ongoing improvements in manufacturing, genetic engineering, and combination therapy strategies, TIL therapy is poised to expand its indications and become a key modality in solid tumor immunotherapy.