Effects of Treatment of High-Grade Serous Ovarian Cancer Tumors at the Single-Cell Level

Abstract

High-grade serous ovarian cancer (HGSOC) is a major health concern for women due to its subtle onset, aggressive progression, high recurrence rate, and resistance to standard therapies. Olaparib, a PARP inhibitor, is currently used as maintenance therapy following removal of tumors. C26A6 is a promising therapeutic which has been shown to inhibit breast cancer progression in mouse models by disrupting the SND1–MTDH interaction. The aim with this study was to investigate the effects oftreatment of Olaparib and C26A6, individually and in combination, in HGSOC tumors in mice at a single-cell level. The project also aimed to compare single-cell transcriptomics with bulk proteomics analysis performed on the same mice. Prior to this study, mice bearing tumors induced by injection of BPPNM HGSOC cells were subjected to treatment with Olaparib and C26A6, alone and in combination, and the primary tumors were analyzed using bulk proteomics via mass spectrometry and
single-cell RNA sequencing (scRNA-seq) using the 10X Genomics platform. Following scRNA-seq preprocessing, differential expression analysis identified cluster-specific gene signatures used for cell type assignment. Differential gene expression and gene set enrichment analysis were further applied for each cell type to assess the treatment responses. The combination treatment had a greater effect on the cancer cells than either treatment alone through the downregulation of extracellular matrix organization, induction of cellular stress and DNA damage as well as activation of pro-inflammatory pathways. While less than 6% of the HGSOC tumors consisted of cancer cells, the tumor microenvironment was dominated by stromal cells and cancer associated fibroblasts.

Popular Abstract

Single-Cell Insights into a Promising Drug Combination Targeting Resistant Ovarian Cancer

High-grade serous ovarian cancer is one of the most aggressive and hard-to-treat forms of ovarian cancer. It often returns after initial therapy, and when it does, it becomes even more resistant. This study explores a promising new drug combination that makes it more difficult for the cancer to survive, offering hope for more effective treatment options.

Before this study, two different drugs were tested on mice bearing high-grade serous ovarian cancer tumors. One of the drugs, Olaparib, is currently used as a maintenance treatment for patients who have already received other therapies, and the other, C26A6, has previously shown anti-cancer effects in mouse models of various cancer types. These drugs were tested both alone and in combination. After a few weeks of treatment, tumor samples were collected to investigate the biological effects of the drugs. To understand how the treatment affected the tumors, the samples were analyzed in bulk and at the single-cell level. This part of the study focused on two important biological molecules:
RNA and proteins. RNA acts like a messenger, which carries instructions from DNA to create proteins, which are the workers inside cells that carry out vital functions. By studying both RNA and proteins, it was possible to see how different cells in the tumor responded to the treatments at a molecular level.

For this project, single-cell RNA analysis was performed to provide insight into how the activity changed across different cell types in response to the treatment. These results were compared to protein data, which measured the average expression across all cells. The results were interesting, as the combination treatment appeared to have a much stronger effect than either drug alone. It didn’t just weaken the cancer cells, it also seemed to trigger an immune response and cause stress in the tumor environment, making it harder for the cancer to survive. The study also showed that only a small portion of the tumor consisted of actual cancer cells, which highlights the importance of investigating tumors at the single-cell level to fully understand the treatment effects. The rest of the tumor was made up of other cell types, now seen as crucial players in how the cancer grows, and how it might be stopped. Another key finding was that although RNA and protein expression showed some similarities, they did not fully correlate. Therefore, analyzing both is important to truly understand the complexity of high-grade serous ovarian cancer.

To summarize, the findings suggest that combining these two drugs could be a powerful strategy to treat this aggressive and deadly form of ovarian cancer. The next steps include studying how non-cancerous cells are affected, and whether the treatment can also stop tumors that have spread to other parts of the body.

While more research is needed before this approach reaches the clinic, the results offer promising insight into how high-grade serous ovarian cancer might be treated more effectively in the future.

• author: Ernestål, Elsa
• supervisor: Fredrik Levander; Parisa Esmaeili; Yuan Li
• organization: Department of Immunotechnology
• course: KIMM05 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Ovarian cancer, High-grade serous ovarian cancer, Single-cell transcriptomics, Proteomics
• language: English
• id: 9213166
• date added to LUP: 2025-09-26 14:16:23
• date last changed: 2025-09-26 14:16:23