How treatment-altered support cells influenced prostate and ovarian cancer cells

A cell can stop dividing without becoming biologically silent. That tension sits at the center of a study published on December 13, 2022, about prostate and ovarian cancer. The researchers examined whether chemotherapy could leave nearby fibroblasts — connective-tissue support cells — in a senescent state, meaning they had stopped growing but continued releasing signals that affected neighboring cancer cells.

The work was laboratory research using human-derived fibroblasts, cancer cell lines and culture-liquid transfer experiments. It also included a separate comparison of archived patient tissues. Together, the experiments establish an early mechanistic link between chemotherapy-exposed support cells and several aggressive behaviors measured in cancer cells. They do not test a senolytic treatment in patients.

A growth arrest that did not silence the fibroblasts

The researchers created two stromal models. For the prostate model, they used human prostate fibroblasts isolated from surgical tissue of patients with benign prostatic hyperplasia. For the ovarian model, they used fibroblasts isolated from healthy peritoneal tissue collected during cytoreductive surgery for advanced ovarian cancer. Those ovarian fibroblasts were support cells from healthy-appearing peritoneal tissue, not ovarian cancer cells.

The fibroblasts were exposed for 24 hours to one of two chemotherapy drugs. Prostate fibroblasts received docetaxel, also called Taxotere, while ovarian-model fibroblasts received cisplatin. The cells were then kept without the drug for six more days. This schedule allowed the researchers to examine whether the treatment left a continuing cellular state rather than only a short-lived response to drug exposure.

Under these culture conditions, both drug treatments produced stable growth arrest. The fibroblasts also showed several features associated with senescence: increased beta-galactosidase staining, accumulation of DNA-damage foci and higher levels of the cell-cycle inhibitors p21 and p16. These measurements supported the conclusion that the chemotherapy-exposed fibroblasts had entered a persistent senescence-like state.

The arrested cells were still active in another sense. They increased expression of secreted factors associated with the senescence-associated secretory phenotype, including the cytokines IL-6 and IL-8, the growth factor VEGF-A and the protease MMP-3. MMP-2 activity increased in docetaxel-treated prostate fibroblasts, with a similar trend in cisplatin-treated ovarian-model fibroblasts. These molecules were not presented as a single proven explanation for every cancer-cell response. They showed that the fibroblasts had changed the signals they released after treatment.

Metabolism showed that the arrested cells remained active

The study also examined how therapy-induced senescence changed fibroblast energy handling. Treated fibroblasts used more oxygen overall and at baseline, but the portion of oxygen consumption linked to ATP production did not increase. In other words, higher oxygen use did not mean that the cells were making more useful energy through mitochondrial respiration.

The researchers observed increased proton leak in docetaxel-treated prostate fibroblasts, a measurement consistent with less efficient mitochondria. Docetaxel-treated prostate fibroblasts showed higher extracellular acidification, and lactate accumulated in the medium from both treated fibroblast models, findings consistent with a shift toward glycolytic metabolism. The study linked these changes with oxidative stress and mitochondrial dysfunction.

These metabolic observations help explain how a cell that has stopped multiplying might still influence its surroundings. They describe accompanying changes in the treated fibroblasts, however, rather than identifying metabolism as the necessary cause of the cancer-cell effects measured later.

Culture liquid carried the effect to cancer cells

To test whether the altered fibroblasts could affect cancer cells without direct contact, the researchers collected the liquid in which the fibroblasts had been cultured. This conditioned medium contains substances released by the fibroblasts but not the fibroblast cells themselves. They then applied it to separate prostate and ovarian cancer cell cultures for 72 hours.

Conditioned medium from the treated prostate fibroblasts increased the movement of PC3 and DU-145 prostate cancer cells. It also increased their ability to pass through a laboratory barrier coated or uncoated to measure invasive and migratory behavior. In the ovarian model, conditioned medium from treated fibroblasts produced comparable increases in measured movement and invasion in SKOV-3 and A2780 ovarian cancer cells.

The researchers also tested colony formation. This assay asks whether cancer cells can establish colonies under culture conditions, providing a measure of continued growth potential in the laboratory. Conditioned medium from the therapy-treated fibroblasts supported colony formation by both prostate and ovarian cancer cells.

The experiment therefore separated two populations and transferred only the fibroblasts’ culture liquid between them. It showed that signals released by the treated support cells were sufficient to increase several measured cancer-cell behaviors. Those behaviors are relevant to aggressiveness in a laboratory model, but they are not the same as demonstrating metastasis or relapse in the patients whose tissues were later examined.

The clearance test narrowed the effect

The next question was whether removing the senescent fibroblasts could reduce the activity carried by their culture liquid. After chemotherapy exposure, the researchers treated the fibroblast cultures with navitoclax, a senolytic drug used in the experiment to clear senescent cells. Beta-galactosidase staining indicated that the senescent fibroblast population was reduced after this treatment.

The researchers then compared conditioned medium from senescent fibroblasts with and without navitoclax treatment. When this medium was applied to PC3 prostate cancer cells and SKOV-3 ovarian cancer cells, medium from the cleared cultures had less ability to increase cancer-cell motility. The intervention therefore weakened the movement-promoting activity associated with the senescent fibroblasts.

This was a targeted laboratory result. The supplied experiments support reduced motility-promoting activity after fibroblast clearance, not the reversal of every aggressive behavior previously measured. Navitoclax was tested in the fibroblast culture sequence, not as an added treatment whose safety or benefit was evaluated in people receiving chemotherapy.

Patient tissues added a separate human comparison

The researchers also asked whether chemotherapy-treated tumors contained more senescence-associated material in their stromal compartments. They examined archived tissue from two patient groups for each cancer type: 10 patients who had received chemotherapy before surgery and 10 untreated comparison patients.

For prostate cancer, the chemotherapy group had received neoadjuvant Taxotere before radical prostatectomy. Compared with the untreated group, these tissues showed more lipofuscin-positive spots in the stromal, non-tumor compartment. Lipofuscin accumulation was used as a marker associated with senescent cells, and additional staining supported its localization in the stroma.

The ovarian comparison involved patients with high-grade serous ovarian cancer. The treated group had received carboplatin plus paclitaxel before cytoreductive surgery, while the laboratory ovarian fibroblast experiment had used cisplatin. That difference matters: the patient-tissue regimen was not the same drug combination as the culture treatment. In the archived ovarian samples, lipofuscin accumulation was greater in the stromal or Pax8-negative compartment of treated tissues than in untreated tissues.

The fibroblast experiments themselves drew on cells from three prostate donors and four ovarian donors. The archived tissue comparisons were separate groups rather than paired samples taken from the same patients before and after treatment. Their contribution is an association between treatment history and greater stromal senescence-associated staining. They do not establish that the staining caused a later clinical outcome, nor do they show that the navitoclax sequence would work in a living tumor.

How targeting support cells could improve cancer treatment

The study suggests a possible treatment sequence: first attack cancer cells with chemotherapy, then remove support cells that have been pushed into a senescent, signal-releasing state. In principle, combining those steps could reduce the ability of treatment-altered stroma to encourage cancer-cell movement and growth in culture.

For people with prostate or ovarian cancer, that approach could eventually offer more durable responses and fewer recurrences if the relevant effects are reproduced in living tumors, stromal clearance can be delivered safely and clinical studies show a genuine improvement in patient outcomes. As of December 2022, the evidence had reached the laboratory mechanism stage. The promise lay in interrupting a communication route between cancer cells and their surroundings, not in a proven senolytic therapy.

Key Sources

• Primary source: Therapy-Induced Stromal Senescence Promoting Aggressiveness of Prostate and Ovarian Cancer.
  DOI or Journal Page · Peer-Reviewed Paper · 2022-12-13