Is the Answer to Cancer an Immune Defense Enhancer?

Traditional cancer therapies such as chemotherapy are effective in obliterating tumor cells; however, their destruction is not selective. The death of normal, healthy tissue results in the adverse side effects we’re familiar with such as vomiting, hair loss, infection, and anemia. Radiation, on the other hand, is more localized but nearby normal cells are commonly affected. What if we could exclusively target cancerous cells, leaving the healthy surrounding tissue intact? Immunotherapy is a promising technique that is being analyzed both in laboratory and clinical settings to do just that.

Particularly, researchers have been experimenting with cancer vaccines containing specific oncogenic antigens to train the immune system to attack its own tumor. Immune system evasion is one of the many hallmarks of cancer; therefore, activating the host’s effector cells through antigen exposure will result in enhanced tumor recognition and destruction. Similar to vaccines for the chicken pox or the flu, cancer vaccines boost the body’s natural defense mechanisms. However, instead of acting as a preventative measure, immunotherapy will treat the already acquired cancer at various stages. Breast cancer in particular has proven to be an effective target for vaccine therapy given the clear evidence of the immune system in breast cancer pathogenesis.

There are several known self- and tumor-specific antigens associated with breast cancer including HER2, carcinoembryonic antigen (CEA), and mucin-1 (MUC-1) that have been used to construct therapeutic vaccines. However, mammaglobin-A (MAM-A) is a highly attractive target because it is expressed almost exclusively in breast cancer and absent or expressed at very low levels in normal tissues. This is key to avoid harming our normal, healthy cells. MAM-A overexpression is evident in 40-80% of breast cancers—spanning noninvasive, invasive, and metastatic cancers. On top of that, this glycoprotein is highly immunogenic, meaning our body readily identifies MAM-A as a foreign particle that needs to be eliminated. From the looks of it, the MAM-A DNA vaccine appears safe and has the potential to yield beneficial results in breast cancer patients. Washington University School of Medicine plans to conduct a phase 1b clinical trial with an estimated 60 participants to further analyze the safety and efficacy of the cancer vaccine. Stay tuned.

Furthermore, researchers are also testing vaccines for many other cancers including but not limited to brain tumors, melanoma, pancreatic and prostate cancer. Interestingly, some cancer vaccines are constructed from the patient’s very own tumor sample instead of the specific antigens on the tumor cells. An FDA-approved prostate cancer vaccine called sipuleucel-T is based on the same concept in that it takes an individualized approach to treatment. Specifically, leukocytes are extracted from the patient, modified to recognize and attack prostate cancer cells, then injected back into the patient’s blood stream. Like a blood transfusion, this is a much less invasive approach as compared to vaccines constructed with a tumor sample obtained through surgery.

Unfortunately, developing therapeutic vaccines for cancer is not an easy task given the innate characteristics of the disease—avoiding immune destruction, sustaining proliferative signaling, resisting cell death, and activating invasion and metastasis among others. Therefore, researchers are using adjuvants in conjunction with vaccine therapy to elicit an enhanced immune response and counter cancer immune evasion. Doctors are also utilizing vaccine therapy in combination with other traditional treatments to eradicate metastatic or more aggressive cancers.

A future in which we are able to treat breast cancer— the second leading cause of cancer death in women—by manipulating the incredible function of the immune system is fast approaching. In fact, cracking the code to all cancers in an approach that still maintains quality of life in patients is right at our fingertips.

If you want to learn more about the future of breast cancer therapy, there may be a solution to reduce or forgo chemotherapy.

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Elizabeth Arruda

Is a contributor to The Almost Doctor’s Channel.