Immunotherapy: A Promising Cancer Therapy

Cancer cells have their own ways and tricks to skip our defense system. Immunotherapy helps to overcome these tricks and destroy cancer cells.

Overview

Our immune system plays a critical role in protecting us from a variety of health threats, including infectious bacteria, viruses, and even cancer. However, cancer cells have developed mechanisms to evade detection by the immune system. Immunotherapy is a groundbreaking treatment that helps the immune system overcome these tricks, enabling immune cells to identify and destroy cancer cells more effectively. This innovative approach has shown great promise as an alternative or complement to traditional cancer treatments like chemotherapy and radiation therapy.

Figure (1)

Traditional therapy vs. Immunotherapy.

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Why is Immunotherapy Important?

As mentioned earlier, cancer cells can evade the immune system through various mechanisms. In some cases, the immune system might fail to recognize cancer cells as harmful because they originate from normal, healthy tissue. Additionally, cancer cells can alter the tumor microenvironment to make it more hostile to immune cells or secrete substances that suppress immune activity.

However, the challenge is not only with the cancer cells. The immune system itself has limitations that can impact its ability to mount an effective response. These limitations can include:

Immune Tolerance: Cancer cells often arise from normal cells, which makes it difficult for the immune system to recognize them as "foreign" invaders.
Inadequate Immune Response: Even when the immune system recognizes cancer cells, it may not generate a strong enough response to eliminate them.

Immunotherapy aims to address these challenges by stimulating or enhancing the body's natural immune defenses. This enables the immune system to work more efficiently to locate and destroy cancer cells. By boosting immune activity, immunotherapy represents a transformative step forward in cancer treatment.

Types of Immunotherapy

There are several types of immunotherapy used in cancer treatment. Each type works in a different way to help the immune system target and destroy cancer cells. Some of the main types of immunotherapy include:

Checkpoint Inhibitors: These therapies work by releasing the natural "brakes" on the immune system, allowing immune cells called T cells to recognize and attack tumor cells. Checkpoint inhibitors are a key part of modern cancer immunotherapy.
Adoptive Cell-Based Therapy: This therapy involves the use of immune cells, either natural or modified, to treat cancer. Some common types of adoptive cell-based therapy include:

Chimeric Antigen Receptor (CAR) T-Cell Therapy: In this treatment, T cells are taken from the patient’s blood, modified in the lab with a special virus to better recognize and target cancer cells, and then infused back into the patient to attack the tumor.
Tumor-Infiltrating Lymphocytes (TIL) Therapy: This approach uses white blood cells that have infiltrated the tumor itself. The TILs are extracted, grown in the lab to increase their numbers, and then reintroduced into the patient's body to help fight the cancer.

Cancer Vaccines: Like vaccines for infections, cancer vaccines train the immune system to recognize and attack cancer cells. Cancer vaccines may be used to prevent cancer or to treat existing cancer by enhancing the body’s immune response.
Monoclonal Antibodies (mAbs): These are lab-made antibodies designed to mimic the immune system's natural antibodies. They can target specific molecules on cancer cells, making them useful for both diagnosing and treating certain types of cancer.

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Which Cancers Can Immunotherapy Treat?

Immunotherapy can be effective in treating cancers that have specific markers that the immune system can recognize. These markers make the cancer cells appear "foreign" to the immune system, which allows immunotherapy to work more effectively. Here are some examples of cancers that can be treated with immunotherapy:

Cancers with Many Genetic Changes: Cancers that have significant genetic mutations are often easier targets for immunotherapy because they appear less like normal cells. Examples include melanoma, non-small cell lung cancer (NSCLC), and certain types of colon cancer.
Cancers with High Levels of PD-L1 Expression: PD-L1 is a protein produced by some cancers that suppresses the immune system’s ability to attack tumors. Cancers that express high levels of PD-L1 can be treated with immunotherapy drugs like pembrolizumab and nivolumab (Opdivo). These drugs work by blocking the PD-L1 protein, allowing immune cells to fight the cancer more effectively.
Cancers with Certain Surface Markers: Some cancers have specific surface markers that help immune cells, like CAR T cells, recognize and target cancer cells. For example, the CD19 marker is found on B-cell leukemias, and therapies targeting this marker have shown promising results in treating blood cancers.

Ongoing research is expanding the types of cancers that may benefit from immunotherapy. As scientists continue to understand how the immune system interacts with different cancers, immunotherapy is becoming a more widespread and effective treatment option for a variety of cancer types.

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References

Tan S, Li D, Zhu X. Cancer immunotherapy: Pros, cons and beyond. Biomed Pharmacother. 2020;124:109821.
How Immunotherapy Is Used to Treat Cancer. Available at: https://www.cancer.org/cancer/managing-cancer/treatment-types/immunotherapy/what-is-immunotherapy.html.
Immunotherapy Cancer Treatment. Available at: https://www.mskcc.org/cancer-care/diagnosis-treatment/cancer-treatments/immunotherapy.