Photochemistry and Photobiology

PpIX‐enabled fluorescence‐based detection and photodynamic priming of platinum‐resistant ovarian cancer cells under fluid shear stress

AbstractOver 75% percent of ovarian cancer patients are diagnosed with advanced‐stage disease characterized by unresectable intraperitoneal dissemination and the presence of ascites, or excessive fluid build‐up within the abdomen. Conventional treatments include cytoreductive surgery followed by multi‐line platinum and taxane chemotherapy regimens. Despite an initial response to treatment, over 75% of patients with advanced‐stage ovarian cancer will relapse and succumb to platinum‐resistant disease. Recent evidence suggests that fluid shear stress (FSS), which results from the movement of fluid such as ascites, induces epithelial‐to‐mesenchymal transition and confers resistance to carboplatin in ovarian cancer cells. This study demonstrates, for the first time, that FSS‐induced platinum resistance correlates with increased cellular protoporphyrin IX (PpIX), the penultimate downstream product of heme biosynthesis, the production of which can be enhanced using the clinically approved pro‐drug aminolevulinic acid (ALA). These data suggest that, with further investigation, PpIX could serve as a fluorescence‐based biomarker of FSS‐induced platinum resistance. Additionally, this study investigates the efficacy of PpIX‐enabled photodynamic therapy (PDT) and the secretion of extracellular vesicles under static and FSS conditions in Caov‐3 and NIH:OVCAR‐3 cells, two representative cell lines for high‐grade serous ovarian carcinoma (HGSOC), the most lethal form of the disease. FSS induces resistance to ALA‐PpIX‐mediated PDT, along with a significant increase in the number of EVs. Finally, the ability of PpIX‐mediated photodynamic priming (PDP) to enhance carboplatin efficacy under FSS conditions is quantified. These preliminary findings in monolayer cultures necessitate additional studies to determine the feasibility of PpIX as a fluorescence‐based indicator, and mediator of PDP, to target chemoresistance in the context of FSS.

Photodynamic priming overcomes platinum resistance from short‐term exposure to select perfluoroalkyl substances in endometrial cancer cell lines

AbstractFirst‐line treatment for advanced‐stage or recurrent endometrial cancer consists of platinum‐ and taxane‐based chemotherapy, to which many patients will develop resistance. Determining the factors that contribute to platinum resistance and developing alternate treatment options for patients with advanced‐stage gynecologic malignancies is critical to improving survival outcomes. Recently, we published the first study evaluating the contribution of perfluoroalkyl substances (PFAS) exposure to platinum resistance in endometrial cancer cell lines and found that select PFAS induce carboplatin resistance, potentially by dysregulating mitochondrial function. The present study expands upon those findings by examining the efficacy of photodynamic priming (PDP) in combination with carboplatin to overcome PFAS‐induced platinum resistance. Due to the suspected role of mitochondrial dysfunction in platinum resistance, two clinically approved photosensitizers that, in part, localize to mitochondrial membranes or are synthesized in mitochondria were evaluated: benzoporphyrin derivative (BPD) and aminolevulinic acid‐induced protoporphyrin IX (ALA‐PpIX), respectively. Combination of ALA‐PpIX‐mediated PDP + carboplatin resulted in a greater reduction in survival fraction than the same combination with BPD. While PDP with both photosensitizers reduced mitochondrial membrane potential, the reduction was greater with BPD‐PDP than ALA‐PpIX‐PDP. These findings demonstrate that BPD‐PDP and ALA‐PpIX‐PDP in combination with carboplatin can be used to overcome PFAS‐induced platinum resistance in endometrial cancer cells.

Photochemical Targeting of Mitochondria to Overcome Chemoresistance in Ovarian Cancer†

AbstractOvarian cancer is the most lethal gynecologic malignancy with a stubborn mortality rate of ~65%. The persistent failure of multiline chemotherapy, and significant tumor heterogeneity, has made it challenging to improve outcomes. A target of increasing interest is the mitochondrion because of its essential role in critical cellular functions, and the significance of metabolic adaptation in chemoresistance. This review describes mitochondrial processes, including metabolic reprogramming, mitochondrial transfer and mitochondrial dynamics in ovarian cancer progression and chemoresistance. The effect of malignant ascites, or excess peritoneal fluid, on mitochondrial function is discussed. The role of photodynamic therapy (PDT) in overcoming mitochondria‐mediated resistance is presented. PDT, a photochemistry‐based modality, involves the light‐based activation of a photosensitizer leading to the production of short‐lived reactive molecular species and spatiotemporally confined photodamage to nearby organelles and biological targets. The consequential effects range from subcytotoxic priming of target cells for increased sensitivity to subsequent treatments, such as chemotherapy, to direct cell killing. This review discusses how PDT‐based approaches can address key limitations of current treatments. Specifically, an overview of the mechanisms by which PDT alters mitochondrial function, and a summary of preclinical advancements and clinical PDT experience in ovarian cancer are provided.

Chemophototherapeutic Ablation of Doxorubicin‐Resistant Human Ovarian Tumor Cells†

AbstractPorphyrin‐phospholipid (PoP) liposomes loaded with Doxorubicin (Dox) have been demonstrated to be an efficient vehicle for chemophototherapy (CPT). Multidrug resistance (MDR) of cancer cells is a problematic phenomenon in which tumor cells develop resistance to chemotherapy. Herein, we report that Dox‐resistant tumor cells can be ablated using our previously described formulation termed long‐circulating Dox loaded in PoP liposomes (LC‐Dox‐PoP), which is a PEGylated formulation containing 2 mol. % of the PoP photosensitizer. In vitro studies using free Dox and LC‐Dox‐PoP showed that human ovarian carcinoma A2780 cells were more susceptible to Dox compared to the corresponding Dox‐resistant A2780‐R cells. When CPT was applied with LC‐Dox‐PoP liposomes, effective killing of both nonresistant and resistant A2780 cell lines was observed. An in vivo study to assess the efficiency of LC‐Dox‐PoP showed effective tumor shrinkage and prolonged survival of athymic nude mice bearing subcutaneous Dox‐resistant A2780‐R tumor xenografts when they were irradiated with a red laser. Biodistribution analysis demonstrated enhanced tumoral drug uptake in Dox‐resistant tumors with CPT, suggesting that increased drug delivery was sufficient to induce ablation of resistant tumor cells.

Identification of potential cell surface targets in patient‐derived cultures toward photoimmunotherapy of high‐grade serous ovarian cancer

AbstractTumor‐targeted, activatable photoimmunotherapy (taPIT) has shown promise in preclinical models to selectively eliminate drug‐resistant micrometastases that evade standard treatments. Moreover, taPIT has the potential to resensitize chemo‐resistant tumor cells to chemotherapy, making it a complementary modality for treating recurrent high‐grade serous ovarian cancer (HGSOC). However, the established implementation of taPIT relies on the overexpression of EGFR in tumor cells, which is not universally observed in HGSOCs. Motivated by the need to expand taPIT applications beyond EGFR, we conducted mRNA‐sequencing and proteomics to identify alternative cell surface targets for taPIT in patient‐derived HGSOC cell cultures with weak EGFR expression and lacking expression of other cell surface proteins commonly reported in the literature as overexpressed in ovarian cancers, such as FOLR1 and EpCAM. Our findings highlight TFRC and LRP1 as promising alternative targets. Notably, TFRC was overexpressed in 100% (N = 5) of the patient‐derived HGSOC models tested, whereas only 60% of models had high EpCAM expression, suggesting that future larger cohort studies should include TFRC. While this study focuses on target identification, future work will expand the approaches developed here to larger HGSOC biopsy repositories and will also develop and evaluate antibody‐photosensitizer conjugates targeting these proteins for taPIT applications.

Effect of photodynamic therapy on the expression of toll‐like receptor 2, ‐3, ‐4, and ‐8 in the cervical lesions

Abstract Photodynamic therapy (PDT) is a minimally invasive treatment with low systemic toxicity and immunomodulatory effects, increasingly applied in managing HPV‐associated cervical lesions. Toll‐like receptors (TLRs) are critical in regulating immune responses in cervical pathology, yet their dynamics under PDT remain underexplored. This study investigates the effect of PDT on TLR2, TLR3, TLR4, and TLR8 expression in cervical epithelial cells ex vivo, considering lesion severity. The results reveal that TLR8 exhibited the most significant reduction across all groups 2 h after PDT, with the strongest suppression in patients with invasive cervical cancer. TLR4 expression decreased by 24% in HPV‐infected patients and by 71% in those with cervical cancer, highlighting its potential role in modulating the inflammatory microenvironment post‐PDT. TLR3 showed hyperexpression in LSIL and suppression in HSIL/CIN III, although changes were not statistically significant ( p > 0.05). TLR2 expression remained unchanged, likely due to HPV type variability. These findings demonstrate that PDT effectively reduces hyperexpression of TLR8, TLR4, and TLR3 in early‐stage cervical cancer, suggesting their potential as biomarkers for treatment efficacy. Further research incorporating HPV typing and advanced techniques like liquid biopsy is essential to refine our understanding of TLRs in PDT for HPV‐associated cervical lesions.

Photodynamic Priming Overcomes Per‐ and Polyfluoroalkyl Substance (PFAS)‐Induced Platinum Resistance in Ovarian Cancer†

AbstractPer‐ and polyfluoroalkyl substances (PFAS) are widespread environmental contaminants linked to adverse outcomes, including for female reproductive biology and related cancers. We recently reported, for the first time, that PFAS induce platinum resistance in ovarian cancer, potentially through altered mitochondrial function. Platinum resistance is a major barrier in the management of ovarian cancer, necessitating complementary therapeutic approaches. Photodynamic therapy (PDT) is a light‐based treatment modality that reverses platinum resistance and synergizes with platinum‐based chemotherapy. The present study is the first to demonstrate the ability of photodynamic priming (PDP), a low‐dose, sub‐cytotoxic variant of PDT, to overcome PFAS‐induced platinum resistance. Comparative studies of PDP efficacy using either benzoporphyrin derivative (BPD) or 5‐aminolevulinic acid‐induced protoporphyrin IX (PpIX) were conducted in two human ovarian cancer cell lines (NIH:OVCAR‐3 and Caov‐3). BPD and PpIX are clinically approved photosensitizers that preferentially localize to, or are partly synthesized in, mitochondria. PDP overcomes carboplatin resistance in PFAS‐exposed ovarian cancer cells, demonstrating the feasibility of this approach to target the deleterious effects of environmental contaminants. Decreased survival fraction in PDP + carboplatin treated cells was accompanied by decreased mitochondrial membrane potential, suggesting that PDP modulates the mitochondrial membrane, reducing membrane potential and re‐sensitizing ovarian cancer cells to carboplatin.

Overcoming the effects of fluid shear stress in ovarian cancer cell lines: Doxorubicin alone or photodynamic priming to target platinum resistance

AbstractResistance to platinum‐based chemotherapies remains a significant challenge in advanced‐stage high‐grade serous ovarian carcinoma, and patients with malignant ascites face the poorest outcomes. It is, therefore, important to understand the effects of ascites, including the associated fluid shear stress (FSS), on phenotypic changes and therapy response, specifically FSS‐induced chemotherapy resistance and the underlying mechanisms in ovarian cancer. This study investigated the effects of FSS on response to cisplatin, a platinum‐based chemotherapy, and doxorubicin, an anthracycline, both of which are commonly used to manage advanced‐stage ovarian cancer. Consistent with prior research, OVCAR‐3 and Caov‐3 cells cultivated under FSS demonstrated significant resistance to cisplatin. Examination of the role of mitochondria revealed an increase in mitochondrial DNA copy number and intracellular ATP content in cultures grown under FSS, suggesting that changes in mitochondria number and metabolic activity may contribute to platinum resistance. Interestingly, no resistance to doxorubicin was observed under FSS, the first such observation of a lack of resistance under these conditions. Finally, this study demonstrated the potential of photodynamic priming using benzoporphyrin derivative, a clinically approved photosensitizer that localizes in part to mitochondria and endoplasmic reticula, to enhance the efficacy of cisplatin, but not doxorubicin, thereby overcoming FSS‐induced platinum resistance.