Immune Cells Can Promote Ovarian Cancer Progression, According To New Study

Immune Cells Can Promote Ovarian Cancer Progression, According To New Study

Scientists from Wistar Institute demonstrated that aggressive forms of ovarian cancer have their origin in malignant cells under-controlled by the immune system until one point when they develop metastases. Researchers also found that ovarian cancers do not necessarily overcome the immune system’s ability to suppress them but their uncontrolled proliferation is supported by the activity of dendritic cells. The research evidentiated that it may be possible to restore the suppressing activity of the immune system by depleting the patient’s own dendritic cells.

“Our model shows where the cancer is kept in check for relatively long periods, but once they become noticeable, tumors grow exponentially. More importantly, we show that by depleting these dendritic cells of the immune system, we can reverse the effect, once again allowing our immune system to recognize the ovarian tumors.”, said the leader of the study.

This study will be presented in the March issue of the Journal of Experimental Medicine. With this research, scientist were able to induce ovarian tumors to mice that are respecting the patterns of human forms of ovarian cancers. These patterns were represented by the inflammatory reactions of the surrounding tissues  that ovarian cancer produces in humans.

“Our system uses oncogene-driven tumors that are spontaneously antigenic, thus avoiding the use of artificial foreign antigens that do not accurately replicate what drives anti-tumor immune responses in humans”, said the researchers.

Ovarian cancer represents one of the most fatal form of cancer in woman with no early stages specific symptoms, many women being diagnosed in the advanced stages of the disease. Over the last 40 years an increase in the survival rates for most cancers was observed but for ovarian cancer, the survival rate only improved slightly since 1970’s.

For this study, researchers created their own ovarian cancer model, hoping to better understand how this type of tumor overcomes the immune system and becomes very aggressive.

A tumor that is developing on one ovary is unrecognizable until one moment when the cancerous cells are growing exponentially. This stage according to the study, is equivalent with some phenotypic changes that take place in the dendritic cells of the immune system.

Dendritic Cells

Normally, dendritic cells are part of a worning system of the immune system for potential threats. They are known as antigen-presenting cells, having a very important role in presenting antigens to leukocytes, cells that can respond and combat an infection, or in this particular case, can inhibit tumor developing. This process takes place until dendritic cells switch sides and favor tumor growing.

Scientist observed that when this phenomenon appears, dendritic cells suffer changes that allows ovarian cancer to develop quickly and to metastasize. It was also observed that tumors are still immunogenetic and they can trigger an immune response. Dendritic cells are those that are constantly suppressing anti-tumor cells of the immune system, especially T cells.

The results question the cancer immunoeditting theory according to which the immune system can actively eliminate cancerous cells that are recognized as antigens, thus producing tumor stagnation, until one moment when it becomes symptomatic. In conclusion all tumors that are presenting symptoms are secondary to a failure of the immune system, where tumors lose the capacity to trigger an immune response and to be recognized by the immune system.

The study brings a valuable information that shows that dendritic cells that are depleted in the early stages of ovarian cancer, are favoring tumor expansion, while depleted dendritic cells later in tumor progression stops cancer development. Results suggest that rapid cancer progression is not caused by a loss of tumor immunogenicity, but due to a change in the dendrtic cells which are a part of the immune system.