AAV for ovarian cancer gene therapy

Abstract

Recent advancements in ovarian cancer treatment, particularly with PARP inhibitors, have markedly enhanced the recurrence-free interval, shifting the treatment paradigm and increasing treatment success in patients with BRCA mutations or HRD (homologous recombination deficiency). However, a significant proportion of cases experience relapse, resulting in poorer long-term survival rates when compared to other female cancers, such as breast cancer. This review explores the potential of adeno-associated virus (AAV) vectors for gene therapy in ovarian cancer and examines rational gene therapy strategies by categorizing them based on target cells and target genes to determine the most effective approach for ovarian cancer treatment. Specifically, it examines strategies such as anti-angiogenesis and immune modulation, highlighting the strategy of gene supplementation to hinder ovarian cancer progression. Innovations in AAV capsid design now allow for targeted delivery, focusing on ovarian cancer stem cells (CSCs) identified by specific markers. Additionally, leveraging DNA sequencing technologies enhances the identification and incorporation of therapeutic genes into AAV vectors, promising new avenues for ovarian cancer gene therapy.

Fig. 1. Anatomy and treatment course in advanced ovarian cancer.

A Typical anatomical presentation of FIGO (International Federation of Gynecology and Obstetrics) stage IIIC ovarian cancer. The 5-year survival rate for patients initially diagnosed with stage III ovarian cancer is ~26%. B Schematic representation of CA-125 levels and ovarian tumor burden in stage III high-grade serous ovarian cancer (HGSOC). The standard treatment regimen for ovarian cancer typically involves optimal cytoreductive surgery followed by six cycles of chemotherapy using carboplatin and paclitaxel. Post-chemotherapy, PARP inhibitors may be used as maintenance therapy to prolong progression-free survival (PFS). If the patient experiences a relapse more than 6 months after completing the initial chemotherapy, it is classified as a platinum-sensitive relapse, allowing for the same platinum- and taxane-based chemotherapy regimen to be reused. Conversely, if the relapse occurs within six months, it is considered a platinum-resistant relapse. In these cases, targeted therapies such as bevacizumab, combined with agents like pegylated liposomal doxorubicin (PLD), gemcitabine, or topotecan, are often utilized. Typically, PFS decreases with each successive relapse of ovarian cancer, eventually leading to a stage where no effective treatments remain, resulting in patient mortality. Therefore, extending the PFS following the initial chemotherapy is crucial for improving outcomes in ovarian cancer treatment. Promising gene therapy has the potential to significantly increase this initial PFS by targeting specific pathways involved in tumor progression.

Fig. 2. Comparison of wild-type AAV and recombinant AAV.

A Schematic representation of wild-type AAV, featuring its single-stranded viral genome. The wild-type AAV genome comprises single-stranded DNA with two inverted terminal repeats (ITRs) at either end and includes the essential genes Rep and Cap for viral replication. This genome produces at least three different transcript variants, each originating from distinct starting points. The p5 and p19 promoters are responsible for transcribing mRNA for the Rep78, Rep68, Rep52, and Rep40 proteins, while the p40 promoter transcribes the genes for the viral capsid proteins VP1, VP2, and VP3, as well as the non-structural proteins AAP and MAAP, which are crucial for virus production. B Production of recombinant AAV and its representative structure. To produce AAV, a eukaryotic cell, such as a HEK293T cell, is transfected with an AAV transgene plasmid containing the therapeutic gene intended for gene therapy, a Rep/Cap plasmid derived from wild-type AAV, and a helper plasmid derived from adenovirus that contains genes promoting efficient AAV production. After allowing sufficient time for the cells to produce AAV particles, AAV is harvested and purified from the cell lysate and supernatant. This process results in the generation of functional recombinant AAV capable of therapeutic gene expression in the host. Unlike wild-type AAV, recombinant AAV cannot replicate or propagate after transducing the host cell due to the absence of Rep/Cap genes.

Fig. 3. AAV gene therapy strategies for targeting ovarian cancer cells: focus on gene supplementation.

Schematic representation of gene therapy strategies targeting ovarian cancer cells using AAV. The strategies are categorized based on the target cells and the specific gene therapy approaches employed. The diagram highlights the engineering of AAV capsids to selectively target ovarian cancer stem cells or immune cells. Additionally, functional screening of therapeutic genes could be conducted using an in vivo ovarian cancer model with AAV to identify potential therapeutic genes, including antibodies, anti-angiogenic factors, cytokines, and secretory tumor suppressors.

Fig. 4. Schematic overview of therapeutic application and mechanism of AAV gene therapy targeting ovarian cancer.

A This schematic illustrates a conceptual framework for incorporating AAV-based gene therapy into the current standard treatment regimen for ovarian cancer. Following maximal cytoreductive surgery and adjuvant chemotherapy with paclitaxel and carboplatin, AAV gene therapy—targeting angiogenesis or immune modulation pathways—is administered either in parallel with or sequentially after chemotherapy. The addition of gene therapy aims to enhance the durability of treatment response and significantly extend the duration of PFS beyond what is typically achieved with chemotherapy alone. This strategy addresses the critical need for therapeutic interventions that can delay relapse and improve long-term outcomes in ovarian cancer patients. B This illustration depicts the proposed molecular mechanism of AAV-mediated gene therapy targeting ovarian cancer. AAV vectors can be administered either intravenously (IV) or intraperitoneally (IP). Although the evaluation of administration routes lies beyond the scope of this review, it remains a critical consideration due to the anatomical characteristics of ovarian cancer, which predominantly resides within the peritoneal cavity. Determining the more effective route for AAV delivery—IV or IP—may significantly influence therapeutic efficacy. Engineered AAV capsids capable of efficiently infecting residual, microscopic ovarian cancer cells following maximal cytoreductive surgery can facilitate the delivery and expression of therapeutic genes within both ovarian tumor cells and cancer stem cells. Ideally, the anti-cancer proteins encoded by these genes should exert not only cell-autonomous anti-tumor effects in transduced cells, but also paracrine effects on neighboring malignant cells, thereby enhancing the overall therapeutic response.