Liposomes hold great potential as gene and drug delivery vehicles due to their biocompatibility and modular properties, coupled with the major advantage of attenuating the risk of systemic toxicity from the encapsulated therapeutic agent. Decades of research have been dedicated to studying and optimizing liposomal formulations for a variety of medical applications, ranging from cancer therapeutics to analgesics. Some effort has also been made to elucidate the toxicities and immune responses that these drug formulations may elicit. Notably, intravenously injected liposomes can interact with plasma proteins, leading to opsonization, thereby altering the healthy cells they come into contact with during circulation and removal. Additionally, due to the pharmacokinetics of liposomes in circulation, drugs can end up sequestered in organs of the mononuclear phagocyte system, affecting liver and spleen function. Importantly, liposomal agents can also stimulate or suppress the immune system depending on their physiochemical properties, such as size, lipid composition, pegylation, and surface charge. Despite the surge in the clinical use of liposomal agents since 1995, there are still several drawbacks that limit their range of applications. This review presents a focused analysis of these limitations, with an emphasis on toxicity to healthy tissues and unfavorable immune responses, to shed light on key considerations that should be factored into the design and clinical use of liposomal formulations.

Ascites refers to the abnormal accumulation of fluid in the peritoneum resulting from an underlying pathology, such as metastatic cancer. Among all cancers, advanced-stage epithelial ovarian cancer is most frequently associated with the production of malignant ascites and is the leading cause of death from gynecologic malignancies. Despite decades of evidence showing that the accumulation of peritoneal fluid portends the poorest outcomes for cancer patients, the role of malignant ascites in promoting metastasis and therapy resistance remains poorly understood. This review summarizes the current understanding of malignant ascites, with a focus on ovarian cancer. The first section provides an overview of heterogeneity in ovarian cancer and the pathophysiology of malignant ascites. Next, analytical methods used to characterize the cellular and acellular components of malignant ascites, as well the role of these components in modulating cell biology, are discussed. The review then provides a perspective on the pressures and forces that tumors are subjected to in the presence of malignant ascites and the impact of physical stress on therapy resistance. Treatment options for malignant ascites, including surgical, pharmacological and photochemical interventions are then discussed to highlight challenges and opportunities at the interface of drug discovery, device development and physical sciences in oncology.

Targeting the tumor microenvironment (TME) provides opportunities to modulate tumor physiology, enhance the delivery of therapeutic agents, impact immune response and overcome resistance. Photodynamic therapy (PDT) is a photochemistry‐based, nonthermal modality that produces reactive molecular species at the site of light activation and is in the clinic for nononcologic and oncologic applications. The unique mechanisms and exquisite spatiotemporal control inherent to PDT enable selective modulation or destruction of the TME and cancer cells. Mechanical stress plays an important role in tumor growth and survival, with increasing implications for therapy design and drug delivery, but remains understudied in the context of PDT and PDT‐based combinations. This review describes pharmacoengineering and bioengineering approaches in PDT to target cellular and noncellular components of the TME, as well as molecular targets on tumor and tumor‐associated cells. Particular emphasis is placed on the role of mechanical stress in the context of targeted PDT regimens, and combinations, for primary and metastatic tumors.

Highlights Combination of olaparib and photodynamic therapy is effective in reducing the number and clonogenic survival of ovarian cancer cells. Photodynamic therapy using a lipidated photosensitizer reduces the selective advantage of olaparib-resistant ovarian cancer cells. Photodynamic therapy potentiates the DNA-damaging effects of olaparib.

No abstract

The combination of photodynamic therapy and taxol‐ or platinum‐based chemotherapy (photochemotherapy) is an effective and promising cancer treatment. While the mechanisms of action of photochemotherapy are actively studied, relatively little is known about the cytotoxicity and molecular alterations induced by the combination of chemotherapy and photosensitizers without light activation in cancer cells. This study investigates the interplay between the photosensitizer benzoporphyrin derivative (BPD) without light activation and cisplatin or paclitaxel in two glioblastoma lines, U87 and U251. The combination effect of BPD and cisplatin in U87 cells is slightly synergistic (combination index, CI = 0.93), showing 1.8‐ to 2.6‐fold lower half‐maximal inhibitory concentrations (IC50) compared to those of individual drugs. In contrast, combining BPD and paclitaxel is slightly antagonistic (CI = 1.14) in U87 cells. In U251 cells, the combinations of BPD and cisplatin or paclitaxel are both antagonistic (CI = 1.24 and 1.34, respectively). Western blotting was performed to investigate changes in the expression levels of YAP, TAZ, Bcl‐2 and EGFR in U87 and U251 cells treated with BPD, cisplatin and paclitaxel, both as monotherapies and in combination. Our study provides insights into the molecular alterations in two glioma lines caused by each monotherapy and the combinations, in order to inform the design of effective treatments.

The combination of photodynamic agents and biological inhibitors is rapidly gaining attention for its promise and approval in treating advanced cancer. The activity of photodynamic treatment is mainly governed by the formation of reactive oxygen species upon light activation of photosensitizers. Exposure to reactive oxygen species above a threshold dose can induce cellular damage and cancer cell death, while the surviving cancer cells are “photodynamically primed”, or sensitized, to respond better to other drugs and biological treatments. Here, we report a new combination regimen of photodynamic priming (PDP) and prostaglandin E2 receptor 4 (EP4) inhibition that reduces the migration and invasion of two human ovarian cancer cell lines (OVCAR-5 and CAOV3) in vitro. PDP is achieved by red light activation of the FDA-approved photosensitizer, benzoporphyrin derivative (BPD), or a chemical conjugate composed of the BPD linked to cetuximab, an anti-epithelial growth factor receptor (EGFR) antibody. Immunoblotting data identify co-inhibition of EGFR, cAMP-response element binding protein (CREB), and extracellular signal-regulated kinase 1/2 (ERK1/2) as key in the signaling cascades modulated by the combination of EGFR-targeted PDP and EP4 inhibition. This study provides valuable insights into the development of a molecular-targeted photochemical strategy to improve the anti-metastatic effects of EP4 receptor antagonists.

No abstract