Ovarian Cancer Fluid Helps Tumors Evade Cell Death

Ascites in ovarian cancer may do far more than signal advanced disease. Researchers found the fluid actively rewires tumor metabolism to protect cancer cells from ferroptosis and fuel metastatic spread, while revealing a possible therapeutic weakness. 

Study: Ascites protects against ferroptosis and enables the peritoneal growth of ovarian cancer. Image credit: Niwat.koh/Shutterstock.com

A recent study published in Nature Communications suggests that ascites, or fluid buildup in the abdomen, observed in advanced ovarian cancer (OVCA), is more than just a side effect of the disease. The fluid may help cancer cells survive and spread by protecting them from ferroptosis, a regulated form of iron-dependent cell death driven by lipid damage.

The fluid alters lipid and iron metabolism in these cells, making them more resistant. However, fibrate drugs that alter lipid metabolism could reverse some of these effects in laboratory models, highlighting a potential new therapy for metastatic OVCA.

Abdominal Fluid May Fuel Cancer Spread

Ovarian cancer frequently spreads inside the abdomen. This region is also a common site of ascites. A few studies suggest that this fluid could support tumor growth and spread by creating a growth-promoting and immune-evasive environment. However, the underlying mechanisms by which the fluid can favor tumor metastasis are poorly understood. Scientists believe that OVCA cells are especially vulnerable to ferroptosis. This makes their survival during metastasis surprising.

Ascites Effects In Tumor Models

In the present study, researchers investigated whether this fluid buildup helps OVCA cells survive and spread. They also explored the biological basis for these actions.

The team exposed various OVCA cell lines to ascites fluid obtained from patients. These included patient-derived tumor cells and laboratory-grown tumors or organoids. They then triggered ferroptosis using several drugs. They also used gene-editing techniques. These included clustered regularly interspaced short palindromic repeats (CRISPR)-based removal of the glutathione peroxidase 4 (GPX4) gene.

The researchers examined alterations in fat and iron levels that helped tumor cells survive. They also explored changes in gene activity and expression associated with these effects. They also investigated whether the fluid protected against other types of cell death and from cisplatin, a commonly used chemotherapy drug.

The researchers further confirmed whether the effects were truly associated with OVCA-related ascites. They did so by comparing fluid samples obtained from OVCA patients to those collected from liver cirrhosis patients. They also verified the findings using functional three-dimensional models replicating real patient tumors.

The team conducted several animal experiments. They injected OVCA cells into mice, with or without ascites fluid to investigate whether the fluid helped tumor cells grow inside the abdomen. They used bioluminescence and growth markers to track tumor changes. They also checked for any signs of cell damage and fat oxidation in the tumor cells. They further removed substances from the fluid one by one to identify the types of molecules, thereby making tumor cells harder to kill.

RNA Sequencing Reveals Ferroptosis Survival Mechanisms

The team performed several molecular-level tests. These included ribonucleic acid sequencing (RNA-seq), liquid chromatography-based mass spectrometry, and gene-silencing experiments. The tests helped identify pathways and molecular mechanisms that protect tumor cells from iron-mediated cell death. The researchers additionally investigated whether fat-lowering fibrate drugs could block the protective effects in the tumor models and mice.

Lipid Droplets Help Tumors Survive Oxidative Damage

The researchers observed that ascites fluid, even in small amounts, could strongly protect OVCA cells from ferroptosis. The fluid helped cancer cells survive treatments that induced ferroptosis. These included erastin, RSL3, IKE, and JKE-1674. The fluid, however, could not protect the cells from other forms of cell death or from cisplatin, suggesting a specific effect.

Ascites reduced harmful lipid peroxidation in the tumor cells and lowered levels of biological markers linked to ferroptosis, such as ChaC Glutathione Specific Gamma-Glutamylcyclotransferase 1 (CHAC1). Even brief exposure to ascites protected the tumor cells for prolonged periods, even after the fluid was removed.

Ascites Accelerated Tumor Growth In Mouse Models

In mice, ascites promoted OVCA cell growth in the abdomen and shortened survival. Cancer cells, which are usually sensitive to iron-dependent cell killing, could form tumors again in the presence of ascites. The fluid helped tumor cells build ‘lipid droplets’ which shielded the cells from damage. Supporting this, removing the lipid components from the fluid, but not proteins and small molecules, eliminated this protection. Fat transport systems involving high-density lipoprotein (HDL) and proteins such as perilipin 2 (PLIN2) also contributed to the protection.

Ascites could alter the activity of genes associated with fat and iron metabolism. The fluid reduced the expression of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2). It also reduced transferrin receptor (TFRC) gene expression. These changes, together, increased fat storage and reduced iron levels. These changes made cancer cells harder to kill. In mice, fibrate drugs could reverse some of these changes, and bezafibrate, combined with ferroptosis-triggering treatments, reduced tumor growth in the abdomen and improved survival.

Ascites May Actively Drive Ovarian Cancer Metastasis

To summarize, the findings suggest that ascites fluid, which accumulates in the abdomen, can actually help cancer cells survive and spread to other sites. The fluid changes how these cells handle fat and iron, and forms lipid droplets that shield tumor cells from iron-based killing. Commonly used lipid-lowering drugs, however, partly counteract these protective effects in preclinical models. This opens new avenues for developing treatments to prevent or halt OVCA metastasis. Future studies could explore whether restoring HMGCS2 activity can improve treatment response and limit cancer spread.

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