Ovarian cancer is one of the most difficult-to-treat cancers because it becomes resistant to chemotherapy over time.

Now, researchers were able to decipher why, potentially leading to new therapies that could enhance ovarian cancer treatment.

The Nature Of Ovarian Cancer

Ovarian tumors contain two types of cells: the bad and the good. The bad cells are called fibroblasts, which impede chemotherapy drugs, rendering the entire tumor resistant to treatment over time. The good cells - immune T cells - reverse just that.

"Most patients will respond to it at first, but everybody develops chemoresistance," says study author J. Rebecca Liu from the University of Michigan. She adds that ovarian cancer is usually diagnosed during the late phase of the disease, making it really hard to treat. Add to that the potential subsequent resistance to therapy, ovarian cancers can indeed be fatal.

What Causes The Resistance?

Previously, researchers thought that the resistance of ovarian cancer is due to genetic alterations. However, in the new study, the team was able to prove that it is not actually the case.

To investigate, the researchers obtained tissue samples from patients with ovarian cancer. They isolated the cells by type to see the environment of the tumor cells in humans and mice. After that, they went back to link their findings to actual patient prognosis.

Decoding The Resistance

Doctors usually recommend platinum-based chemotherapy drug cisplatin to patients with ovarian cancer. During the study, the team found that fibroblasts block platinum; thus, the drug cannot kill tumor cells.

The good cells or immune T cells, however, nullified this mechanism. By infusing immune T cells to the fibroblasts, the tumor cells started to die.

Study author Weiping Zou explains that T cells are the immune system's soldiers. Scientists are very much aware that having lots of these cells gives patients better outcomes. Now, in the new study, they discovered that these cells also have effects on chemotherapy resistance.

Future Treatments

Now, the authors suggest that combining chemotherapy and immunotherapy may have effective impacts on ovarian cancer patients.

Zou says they can see re-educating tumor cells and fibroblasts with T cells after the patient has developed resistance to chemotherapy. After that, doctors may instill the same chemotherapy drug that the patient was first resistant to. However, this time, that resistance has been reversed, making it effective again.

The study is published in the journal Cell.