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What is TIL Therapy?

A cell therapy that may cure cancers

The human immune system is extremely complex. When most people think of the immune system, we think of our body’s ability to fight off the common cold and infections. But what about cancer?

Naturally, the human immune system searches for foreign and abnormal cells in the body, such as cancer. Tumor-infiltrating Lymphocytes (TILs), a type of T-cell, are white blood cells that move from the bloodstream toward tumors present in the body (1). TIL therapy, a type of adoptive T-cell therapy, research extends back into the late 1970s when it was pioneered by Dr. Steven Rosenberg. In 1988, adoptive T-cell therapy introduced how lymphocytes isolated from tumors, specifically melanoma, can exponentially grow in the lab to kill tumors (2,3).

TILs are composed of T cells, B cells, and natural killer cells just to name a few (1,2). TILs can recognize receptors on tumors and will kill cancer cells, but the immune system and signals from the tumor weaken the response of the TILs attacking the tumor. Inside the body, TILs are prevented from fighting off cancerous tumors’ due immunosuppressive molecules in their microenvironment. Therefore, this is why TIL therapy is needed, to expand the body’s immune response ex vivo (4).

TIL therapy

Expanding TILs and re-inoculating cells into the human body boosts the army of TILs in the patient’s body to attack the specific tumor. For TIL therapy, genetic modification of TILs is not needed for TILs to recognize tumor targets since they already carry the capability.

How can your cancer be treated using TIL cell therapy? Currently, only clinical trials offer TIL therapy. Once enrolled into a clinical trial, a tumor biopsy is surgically collected and sent to a specialized lab to isolate TILs from the tissue. To successfully expand TILs, pre-rapid expansion procedure (pre-REP) and rapid expansion procedure (REP) will take place over the course of a few weeks (1,4).

During pre-REP, the biopsied tumor is cut up into small fragments in TIL-selective medium. The number of TILs harvested may vary depending on the location of the tumor. Inhibitors such as contaminated microbes and fiberglass, some areas of the body contain more than others, can also affect how many TILs that can be grown in the lab (4).

Once TILs have finished the initiation phase, TILs will go through a phase of REP. During this period, TILs are exposed to growth factors and irradiated feeder cells. All these factors stimulate TILs for them to rapidly grow so they can be re-inoculated in the patient’s body to treat the cancer (4).

Doctors and researchers reveal they have witnessed long-lasting effects of TIL therapy years after TIL infusions, including eliminating tumors before physicians can detect them on scans, leaving patients in remission for years.

TIL cell therapy is the future of cancer medicine and potentially a cure. Scientists and oncologists around the world are in the great race to be the first to perfect Dr. Rosenberg’s discovery of TIL therapy and relief of this deadly disease.


  1. Boldt, Clayton, and Ph.D. Clayton Boldt. “Til Therapy: 6 Things to Know.” MD Anderson Cancer Center, MD Anderson Cancer Center, 15 Apr. 2021.

  2. Bear AS, Fraietta JA, Narayan VK, O'Hara M, Haas NB. Adoptive Cellular Therapy for Solid Tumors. Am Soc Clin Oncol Educ Book. 2021 Mar; 41:57-65. doi: 10.1200/EDBK_321115. PMID: 34010040.

  3. Ninds, Emily Petrus. “Steven A. Rosenberg, M.D., Ph.D. An Immunotherapy Pioneer Tells All” National Institutes of Health, U.S. Department of Health and Human Services, 8 Apr. 2022,

  4. Zhao Y, Deng J, Rao S, Guo S, Shen J, Du F, Wu X, Chen Y, Li M, Chen M, Li X, Li W, Gu L, Sun Y, Zhang Z, Wen Q, Xiao Z, Li J. Tumor Infiltrating Lymphocyte (TIL) Therapy for Solid Tumor Treatment: Progressions and Challenges. Cancers. 2022; 14(17):4160.

  5. Makalowski, Jennifer, and Hinrich Abke. ‘Adoptive Cell Therapy of Melanoma: The Challenges of Targeting the Beating Heart’. Melanoma - From Early Detection to Treatment, InTech, Jan. 2013. Crossref, doi:10.5772/53619.

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