One of the first-line treatments for HGSOC is surgery. It is usually a debulking surgery performed by a gynecologic oncologist prior to chemotherapy and consists of the macroscopic removal of all disseminated tumor masses within the peritoneal cavity before starting the first round of chemotherapy. The level of primary cytoreduction is one of the most important prognostic factors for survival. It has been shown that removal of metastatic tumors improves overall survival [11,34]. A debulking surgery is considered successful when less than 1 mm of residual tumor remains [35]. Surgery remains one of the best options for patients with HGSOC, although it can be associated with significant comorbidities [36]. Patients with BRCA1/2 mutations, or more broadly with homologous recombination defects, may choose to undergo a risk-reducing salpingo-oophorectomy, which prevents the development of HGSOC in 85–90% of cases [11,37].

Neoadjuvant chemotherapy can be administered prior to surgery to reduce tumor size. However, most commonly, chemotherapy is given after surgery to eliminate remaining cancer cells. All HGSOC patients are recommended to receive chemotherapy regardless of stage. The most used agents are carboplatin, cisplatin, and paclitaxel. The combination of carboplatin and paclitaxel has been the standard of care for the past 20 years [11]. The typical regimen consists of cisplatin 75 mg/m² infusion, plus paclitaxel 135 mg/m² infused over 24 hours, every 3 weeks for a total of 6 cycles [11]. HGSOC is initially platinum-sensitive, but approximately 80% of patients eventually relapse. Heated intraperitoneal cisplatin and paclitaxel have been shown to increase drug penetration into the abdomen, but the clinical benefit of this technique remains unclear and further trials are needed [37].

Poly (ADP-ribose) polymerase inhibitors (PARPi) are now routinely used in combination with chemotherapy. The first FDA approval for PARPi was granted in 2014 for Olaparib as monotherapy in fourth-line treatment. Later, niraparib and rucaparib were also approved in 2016 and 2017, respectively. PARP enzymes are key sensors of DNA damage—both single-strand (SSB) and double-strand breaks (DSB)—and play crucial roles in DNA repair by catalyzing the addition of ADP-ribose at damage sites. This promotes chromatin decompaction and recruitment of proteins involved in base excision repair (BER), NHEJ, or HR. PARP inhibitors exploits the concept of synthetic lethality: two defects that are non-lethal individually become lethal when combined. When PARP proteins are inhibited, unrepaired SSBs convert into DSBs. In the absence of functional BRCA, HR-deficient cells accumulate lethal DSBs, leading to mitotic catastrophe and cell death. Approximately half of HGSOC tumors show features of homologous recombination deficiency [35], but PARPi provide benefit in all patients. Unfortunately, resistance to PARPi can develop. Cancer cells use several strategies to escape treatment, like HR restoration through gene re-expression (e.g., BRCA1/2), epigenetic modifications activation of alternative repair pathways, or rebalancing HR/NHEJ replication fork protection, often via loss of chromatin remodelers [38].

Currently, immune checkpoint inhibitors (ICI) are not part of standard HGSOC treatment. This may be due to low programmed death-ligand 1 (PD-L1) expression, low mutation burden, and weak immunogenicity. However, PARPi such as olaparib can induce PD-L1 expression, potentially sensitizing tumors to ICIs [39].

The MEDIOLA trial showed encouraging anti-tumor activity, and several other trials are ongoing [39] that target growth factors, like VEGF. To target the tumor microenvironment (TME), anti-VEGF therapies such as bevacizumab are also used in combination with chemotherapy. Bevacizumab is a humanized antibody targeting VEGF-A, a key driver of tumor angiogenesis [11]. In the International Collaboration on Ovarian Neoplasms 7 (ICON7) study, adding bevacizumab significantly improved progression-free survival [40].

For women with platinum-resistant disease, mirvetuximab soravtansine-gynx (MIRV) is another treatment option. It is an antibody–drug conjugate targeting folate receptor alpha (FR-α), expressed in ~80% of primary and recurrent EOC. After internalization, the attached anti-tubulin toxin (DM4) disrupts mitosis and induces apoptosis. Toxicity is relatively low due to the specificity for FR-α–positive cells. In the MIRASOL study, MIRV improved median PFS (5.6 vs 3.9 months) and OS (16.5 vs 12.8 months) in platinum-resistant patients. For platinum-sensitive patients, MIRV may be combined with chemotherapy, though more evidence is needed [41].

Many clinical trials are currently exploring new treatments for HGSOC. The DENALI trial (NCT05128825) tests azenosertib, a selective mitosis inhibitor protein kinase Wee1 inhibitor, in platinum-resistant HGSOC [42]. The BEACON trial (NCT03363867) evaluates bevacizumab + atezolizumab + cobimetinib in platinum-resistant patients [43].

Research models
To discover new drugs and their potential effects on the body, research models are very helpful and essential. Since the beginning of research on HGSOC, many of them have been elaborated, either in vitro or in vivo.

Commercial ovarian cancer cell lines are widely used in research due to their ease of culture and relatively low cost. A broad range of these cell lines is readily available from suppliers, enabling a wide variety of experiments, from drug screening and resistance studies to molecular profiling and therapeutic development. Despite their many advantages, these cell lines also have notable limitations. They have typically undergone numerous passages, exposing them to strong selection pressures. As a result, they tend to accumulate additional, often irrelevant mutations, which can compromise the biological relevance of the model and potentially distort experimental results.

A study analyzing the most used ovarian cancer cell lines, primarily in the context of HGSOC research, has shown that SKOV3 and A2780 do not accurately reflect the molecular characteristics of HGSOC. Notably, these cell lines lack TP53 mutations, which are present in approximately 95% of HGSOC cases, and instead carry mutations in other genes such as PI3K, BRAF, or PTEN. Furthermore, they exhibit very few copy number alterations, which contrast sharply with the high genomic instability typically observed in HGSOC.

Interestingly, the less commonly used cell lines, those with few citations on PubMed, are the ones most closely resembling high-grade serous ovarian carcinoma (HGSOC). Kuramochi, human high-grade serous ovarian cancer (OVSAHO), and Seoul National University-119 (SNU119) cell lines all carry TP53 mutations and exhibit a high number of copy number alterations. The selection of a particular cell line depends on several factors, including the study’s objectives and the culture characteristics. For drug testing, considering the molecular profile is particularly relevant, as a high degree of molecular similarity to patient tumors may improve the predictive value for treatment response [3, 44].

Xenografts are widely used as in vivo models in oncology research. They involve the transplantation of human cells, tissues, or organs into immunodeficient mice, enabling the study of tumor growth and therapeutic responses in a living system. To prevent immune rejection of the graft, various strains of immunocompromised mice are employed, including athymic nude mice (which lack T lymphocytes), Severe Combined Immunodeficiency (SCID) mice (deficient in both T and B lymphocytes), and NOD scid gamma mouse (NSG) (NOD/SCID/IL2Rγnull) mice (which lack both adaptive immunity and natural killer cells). These models allow for successful engraftment and development of human tumors in a murine host. Two main approaches are used for tumor implantation. Subcutaneous implantation offers a technically simple procedure and easy monitoring of tumor growth. However, it does not accurately recapitulate the tumor’s native microenvironment, limiting its physiological relevance.

Orthotopic implantation, where tumor cells are engrafted into their original anatomical site (e.g., human ovarian cancer cells into the mouse ovarian bursa), provides a more faithful representation of the tumor microenvironment. Despite the absence of a functional immune system, these models retain some stromal and tissue-specific characteristics that influence tumor behavior. In addition, it allows the study of peritoneal dissemination and ascites formation. Nevertheless, orthotopic models are technically more demanding, particularly for internal organs, and often require advanced imaging modalities such as bioluminescence to monitor tumor progression [3, 35]. This technique can be used as a model for preclinical development. For instance, it has been used to show the capacity of monoclonal antibodies against human VEGF to have a synergistic effect in combination with paclitaxel on tumor growth and ascites formation.

Patient-derived xenografts (PDX) are a particular type of xenograft in which fresh tumor tissue, directly obtained from a patient, is implanted either subcutaneously or orthotopically into immunodeficient mice. The original tumor tissue can originate from a primary tumor, a metastatic site, or represent different clinical stages, such as untreated or chemoresistant disease. Among the available mouse models, NSG mice are commonly used, as they provide higher engraftment success rates. Typically, it takes between 2 to 6 months for the tumor to grow to the maximum authorized size. For example, in the case of HGSOC, the engraftment success rate is approximately 77%. The PDX model represents a major advancement in tumor modeling, as it is capable of preserving key characteristics of the original tumors, such as histology, mutational profile, and DNA copy number. It is commonly used for pre-clinical drug development and drug screening to help clinicians. However, this model also presents several challenges. Over time, the human stromal components can be replaced by murine stroma, which may alter the tumor microenvironment. Furthermore, it is an expensive model that requires the use of animals, specialized equipment, and trained personnel to maintain the mice under appropriate conditions. Additionally, setting up PDX studies takes time due to the regulatory paperwork and organizational complexity involved [3, 35].

In 2021, Iyer, Sonia et al. developed several syngeneic models of high-grade serous tubo-ovarian carcinomas (HGSC) recapitulating the most common features of patients. A syngeneic model consists of implanting a cell line into mice with the same genetic background (C57BL/6), allowing the growth of a tumor in a microenvironment with a complete immune system. The emergence of this kind of model is crucial to investigate the implication of the immune system in the tumor microenvironment in HGSOC and assess the potential efficacy of immune checkpoint blockade therapies already employed in other cancer types. In this case, the transformed murine fallopian tube epithelial (m-FTE) cell line was genetically engineered to be HR-deficient, with a TP53 missense mutation and knockout of BRCA1, PTEN, and neurofibromin (NF1), as well as an overexpression of Myc, called BPPNM. In addition, they created an m-FTE cell line with undetermined HR status called PPNM, with the same mutations as the BPPNM model except the PPBM cell line still has a wild-type BRCA1. They also created three m-FTE HR-proficient models with a p53 mutation, an overexpression of cyclin E1 (CCNE1) and protein kinase B beta (AKT2), and one of the following modifications: bromodomain-containing protein 4 (BRD4) overexpression (BPCA); SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4) overexpression (SPCA); or KRASG12V, an oncogenic mutant form of KRAS, (KPCA).

These models all harbor histopathological and clinical features found in HGSC patients, such as ascites and peritoneal metastasis, showing that they are robust models for HGSOC. Moreover, after an analysis of the immune microenvironments, they demonstrated that it differs according to genotype. The BPPNM type showed more inflammation with a higher rate of CD3-positive cells and more tumor-associated macrophages than the KPCA or PPNM types. On the other hand, KPCA tumors exhibited a tenfold higher rate of exhaustion markers than BPPNM [3, 35, 45]. These exhaustion markers include programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin domain 3 (TIM-3), and T-cell immunoreceptor with Ig and ITIM domains (TIGIT). These markers demonstrate T-cell exhaustion and ensuing poor immunosuppressive efforts against tumor cells.

Genetically engineered animal models include spontaneous animal models. These spontaneous animal models consist of introducing genetic mutations found in the cancer of interest into an animal model to develop a spontaneous tumor. This type of model offers several advantages, such as genetic similarity to the target cancer and development in an animal with a competent immune system. However, it usually takes a long time for the tumor to appear and grow.

To introduce these mutations, various methods are used. Connolly and colleagues developed a transgenic epithelial ovarian cancer model closely resembling HGSC. They achieved this by expressing the early region of Simian Virus 40 (SV40) under the transcriptional control of the Müllerian inhibiting substance type II receptor (MISIIR) gene, which is expressed in the ovary. In this model, 100% of female offspring develop bilateral ovarian tumors after an average of 152 days, showing features similar to HGSC, including peritoneal metastases and ascites formation. This specific model has been used to evaluate the efficacy of the mTOR inhibitor RAD001 in ovarian neoplasms.

Kim and colleagues created a conditional model by deleting endoribonuclease Dicer (DICER)—an essential gene for miRNA processing—and PTEN, using an anti-Müllerian hormone receptor type 2-directed Cre (Amhr2-Cre) and locus of X-over P1 (LoxP) system. Their model is show in Figure 4. These Dicer^flox/flox Pten^flox/flox Amhr2^cre/+ tumors display aggressive development, arising from the fallopian tube, spreading to the ovaries, and metastasizing throughout the abdomen, including the diaphragm, peritoneal membrane, omentum, and even the pancreas. Primary tumors and metastases also show histological similarities to HGSC, such as pleomorphic nuclei, prominent nucleoli, and high mitotic activity. Despite the absence of TP53 mutations, the model appears accurate, as TP53 expression is low. It is possible that DICER deletion mimics the effect of TP53 mutation, given the role of p53 upstream of DICER [3,35,46].