Citations

Photodynamic priming (PDP), a fallout of photodynamic therapy, transiently modulates the tumor microenvironment (TME), enhances therapeutic susceptibility, and promotes immunogenic cell death through the release of damage-associated molecular patterns (DAMPs). Pancreatic ductal adenocarcinoma (PDAC) remains non-responsive to current therapies with a desmoplastic and immunosuppressive TME that limits drug delivery and blunts responses to immune checkpoint blockade. We investigated whether PDP could enhance anti-PD1 therapy responses in PDAC using patient-derived organoids (PDOs). PDOs were treated with Visudyne and red light (25, 75, and 100 J/cm²), followed by assessment of cytotoxicity, DAMP expression (HSP60, calreticulin, HMGB1), and transcriptomic changes. Monocyte-derived dendritic cells (mDCs) from healthy donors were cocultured with PDP-treated (25 J/cm 2 ) PDOs, then with matched naïve T cells. mDC and T cell activation markers were analyzed. Pembrolizumab (anti-PD1) was added to PDO-mDC-T cell cocultures to evaluate combined effects on PDO viability and T cell activation. PDP induced dose-dependent cytotoxicity and upregulated DAMPs. Gene profiling in PDOs showed increased IFN-γ , TNF-α , and CXCL12 , with reduced PD-L1 , TGF-β1 , and FOXP1 expression. mDCs exposed to PDP-treated PDOs upregulated CD40, CD86, and MHC-II, driving activation of CD4 + and CD8 + T cells, evidenced by elevated PD1 expression. Addition of pembrolizumab further decreased PDO viability and amplified effector cytokines ( IFN-γ , TNF-α , FASLG , granzyme B, IL-2 , IL-21 ). PDP was associated with modulation of the PDAC TME toward a more immunogenic phenotype by enhancing tumor immunogenicity, activating dendritic cells and T cells, and potentiating PD1 blockade. These findings provide mechanistic support for further preclinical and clinical evaluation of PDP combined with checkpoint inhibition in PDAC.

Abstract Pancreatic ductal adenocarcinoma (PDAC) is unresponsive to immune checkpoint therapies largely due to immunosuppression mediated by myeloid and lymphoid cells. Effective treatment strategies require, in addition to immune stimulation, the depletion of these immunosuppressive cells and their interactions. Here, we demonstrate for the first time, that a single verteporfin-based photodynamic therapy (PDT) treatment triples median survival in a KPC-PDAC model when combined with anti-PD1 therapy. Mechanistically, apart from reducing CK19 + tumor cells, PDT depletes immunosuppressive myeloid (CD11c+) and lymphoid (FOXP3+) cell populations, by ~ 4- and ~ 18.4-folds, respectively. PDT further disrupts interactions between these immunosuppressive cells, attenuating a key immune-tolerance axis. At the systemic level, PDT reduces splenic immunosuppression through modulation of tumor-derived cytokines. Within this reprogrammed immune-landscape, anti–PD-1 therapy elicits robust CD8 + T-cell responses, reflected by an ~ 6.7-fold increase in the intratumoral CD8+/Treg ratio. Collectively, these findings establish verteporfin-PDT as an immune-priming strategy that complements anti–PD-1 therapy by alleviating immunosuppression in PDAC.

Despite substantial drug development efforts, pancreatic adenocarcinoma (PDAC) remains a difficult disease to treat, and surgical resection is the only potentially curative option. Unfortunately, 80% of patients are ineligible for surgery due to the presence of invasive disease and/or distant metastases at the time of diagnosis. Treatment strategies geared towards reclassifying these patients as surgical candidates by reducing metastatic burden represents the most promising approach to improve long-term survival. We describe a photodynamic therapy (PDT) based approach that, in combination with the first-line chemotherapeutic nab-paclitaxel, effectively addresses distant metastases in three separate orthotopic PDAC models in immunodeficient mice. In addition to effectively controlling local tumor growth, PDT plus nab-paclitaxel primes the tumor to elicit systemic effects and reduce or abrogate metastases. This combination dramatically inhibits (up to 100%) the eventual development of metastases in models of early stage PDAC, and completely eliminates metastasis in 55% of animals with already established distant disease in late-stage models. Our findings suggest that this light activation process initiates local biological and/or physiological changes within the tumor microenvironment that can be leveraged to treat both localized and distant disease, and potentially reclassify patients with previously inoperable disease as surgical candidates.

Abstract Photodynamic priming ( PDP ), a collateral effect of photodynamic therapy, can transiently alter the tumor microenvironment (TME) beyond the cytotoxic zone. Studies have demonstrated that PDP increases tumor permeability and modulates immune‐stimulatory effects by inducing immunogenic cell death, via the release of damage‐associated molecular patterns and tumor‐associated antigens. Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of cancers with a stubborn immunosuppressive TME and a dense stroma, representing a challenge for current molecular targeted therapies often involving macromolecules. We, therefore, tested the hypothesis that PDP’s TME modulation will enable targeted therapy and result in immune stimulation. Using triple‐receptor‐targeted photoimmuno‐nanoconjugate (TR‐PINs)‐mediated PDP , targeting epidermal growth factor receptor, transferrin receptor, and human epidermal growth factor receptor 2 we show light dose‐dependent TR‐PINs mediated cytotoxicity in human PDAC cells (MIA PaCa‐2), co‐cultured with human pancreatic cancer‐associated fibroblasts (PCAFs) in spheroids. Furthermore, TR‐PINs induced the expression of heat shock proteins (Hsp60, Hsp70), Calreticulin, and high mobility group box 1 in a light dose and time‐dependent manner. TR‐PINs‐mediated T cell activation was observed in co‐cultures of immune cells with the MIA PaCa‐2‐PCAF spheroids. Both CD4 + T and CD8 + T cells showed light dose and time‐dependant antitumor reactivity by upregulating degranulation marker CD107a and interferon‐gamma post‐PDP. Substantial tumor cell death in immune cell‐spheroid co‐cultures by day 3 shows the augmentation by antitumor T cell activation and their ability to recognize tumors for a light dose‐dependent kill. These data confirm enhanced destruction of heterogeneous pancreatic spheroids mediated by PDP ‐induced phototoxicity, TME modulation and increased immunogenicity with targeted nanoconstructs.

Abstract Photodynamic therapy (PDT) offers localized focal ablation in unresectable pancreatic tumors while tissues surrounding the treatment volume experience a lower light dose, termed photodynamic priming (PDP). While PDP does not cause tissue damage, it has been demonstrated to promote vascular permeability, improve drug delivery, alleviate tumor cell density, and reduce desmoplasia and the resultant internal pressure in pre-clinical evaluation. Preclinical data supports PDP as a neoadjuvant therapy beneficial to subsequent chemotherapy or immunotherapy, yet it is challenging to quantify PDP effects in clinical treatment without additional imaging and testing. This study investigated the potential of radiomic analysis using CT scans acquired before and after PDT to identify areas experiencing PDT-induced necrosis as well as quantify PDP effects in the surrounding tissues. A total of 235 CT tumor slices from seven patients undergoing PDT for pancreatic tumors were examined. Radiomic features assessed included intensity metrics (CT number in Hounsfield Units) and texture analysis using several gray-level co-occurrence matrix (GLCM) parameters. Pre-treatment scans of tumor areas that resulted in PDT-induced necrosis showed statistically significant differences in intensity and texture-based features that could be used to predict the regions that did respond (paired t-test, response versus no response, p < 0.001). Evaluation of PDP effects on the surrounding tissues also demonstrated statistically significant differences, in tumor mean value, standard deviation, and GLCM parameters of contrast, dissimilarity and homogeneity (t-test, pre versus post, p < 0.001). Using leave-one-out cross validation, six intensity and texture-based features were combined into a support-vector machine model which demonstrated reliable prediction of treatment effects for six out of seven patients (ROC curve, AUC = 0.93). This study provides pilot evidence that texture features extracted from CT scans could be utilized as an effective clinical diagnostic prediction and assessment of PDT and PDP effects in pancreatic tumors. (clinical trial NCT03033225)

Receptor heterogeneity in cancer is a major limitation of molecular targeting for cancer therapeutics. Single-receptor-targeted treatment exerts selection pressures that result in treatment escape for low-receptor-expressing tumor subpopulations. To overcome this potential for heterogeneity-driven resistance to molecular targeted photodynamic therapy (PDT), we present for the first time a triple-receptor-targeted photoimmuno-nanoconjugate (TR-PIN) platform. TR-PIN functionalization with cetuximab, holo-transferrin, and trastuzumab conferred specificity for epidermal growth factor receptor (EGFR), transferrin receptor (TfR), and human epidermal growth factor receptor 2 (HER-2), respectively. The TR-PINs exhibited up to a 24-fold improvement in cancer cell binding compared with EGFR-specific cetuximab-targeted PINs (Cet-PINs) in low-EGFR-expressing cell lines. Photodestruction using TR-PINs was significantly higher than the monotargeted Cet-PINs in heterocellular 3D in vitro models of heterogeneous pancreatic ductal adenocarcinoma (PDAC; MIA PaCa-2 cells) and heterogeneous head and neck squamous cell carcinoma (HNSCC, SCC9 cells) containing low-EGFR-expressing T47D (high TfR) or SKOV-3 (high HER-2) cells. Through their capacity for multiple tumor target recognition, TR-PINs can serve as a unique and amenable platform for the effective photodynamic eradication of diverse tumor subpopulations in heterogeneous cancers to mitigate escape for more complete and durable treatment responses.