Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive desmoplasia which is considered to be a primary cause of treatment resistance observed in these tumors. Desmoplasia also plays a major role in mediating an immunosuppressive microenvironment and restricting immune cell infiltration in PDAC. In this study, using a syngeneic orthotopic immunocompetent KPC PDAC model, we demonstrate that PDT using Visudyne® can alter the tumor microenvironment, enhances immune cell infiltration, significantly reducing tumor growth and increasing survival in combination with anti-PD1.
Pancreatic cancer is the fourth leading cause of cancer deaths. The poor diagnosis, early metastasis, limited drug accumulation in the tumor microenvironment, and acquired resistance to salvage chemotherapeutic cocktails lead to poor clinical outcomes. To overcome this complex problem, personalized combination treatments have been proposed to guide the clinical management of PDAC patients. In this context, we propose the use of novel delivery systems where light is not a mere spectator, but the main character that apart from inducing cytotoxicity also promotes the release of the cargo at the right time in the right place.
In this study, we study the influence of dye to antibody ratio on the imaging and therapeutic performance of an EGFR-targeted dual function conjugate. We further demonstrate the efficacy of the conjugate in identifying tumor depth to guide surgical resections and the ability to eliminate residual microscopic disease through photoimmunotherapy, in a single intra-operative setting.
Precision molecular imaging finds application in the delineation of tumor margins during surgical resection of head and neck cancers (HNCs). Despite the advantages of surgery, there remain challenges in successfully locating tumor margins, resecting the entire tumor volume and treatment of microscopic tumor tissue. The presence of residual tumors, post-surgery, may require additional interventions and often lead to tumor recurrence. While Epidermal growth factor receptor (EGFR) remains a receptor of choice for targeting in HNCs, the heterogeneity in the expression of EGFR often leads to variations in response to targeted therapeutics. To improve visualization and tumor margin delineation during head and neck tumor surgeries, this study demonstrates the development of a molecular targeted theranostic probe combining the complementary features of fluorescence and photoacoustic imaging. The probe: DFAC (Dual Function Antibody Conjugate) comprises of a fluorophore/photosensitizer; Benzoporphyrin derivative (BPD) and a photoacoustic contrast agent; naphthalocyanine (NC) derivative conjugated to an EGFR antibody; Cetuximab. While BPD assists in fluorescence imaging, it can also be used for inducing cytotoxicity, through photodynamic activation in target tissues. The efficacy of DFAC in selective visualization and photodynamic therapy of tumor cells is evaluated on heterocellular 3D tumor spheroids and orthotopic mouse tongue tumors developed from human oral cancer cell lines (CAL27 and SCC4), expressing different levels of EGFR. In summary, this study demonstrates the potential of the theranostic probe (DFAC) to delineate tumor regions for guiding surgical resection and eradicate residual tumor tissue (post-surgery) by photodynamic therapy.
Imaging technologies such as Ultrasound, OCT, MRI and CT are useful for diagnostics and tomographic assessment of therapy response. Fluorescence imaging with its high sensitivity is a promising approach and is extensively used for lesion localization, surgical guidance and monitoring response to therapies. While conjugating fluorophores to antibodies improves specificity, further conjugation of drugs provides a dual function, where fluorescence monitoring may simultaneously reveal drug pharmacokinetics. Fluorescence imaging, however, is limited by low penetration of light, which can be partially overcome by photoacoustic imaging (PAI). In this study, by conjugating a fluorophore and photoacoustic molecule to an antibody (Dual Function Antibody Conjugate (DFAC)), we evaluate whether PAI can significantly improve deep-tissue imaging.
To provide a systematic comparison of these imaging modalities we developed a DFAC, comprising of Cetuximab (anti-EGFR antibody) conjugated with a fluorophore (AF647) and a photoacoustic dye (IRDye800) in a 1:2:2 ratio. We hypothesize that, conjugating quantifiable probes to an antibody, would provide information about different depths within the confines of optical approaches. Such quantification is particularly important in photodynamic therapy, for determination of tissue concentration of photosensitizers and in chemotherapy for quantification of drug concentrations non-invasively. The relationship between the photoacoustic and fluorescence signals from the DFAC is demonstrated through spectroscopic techniques and their EGFR specificity along with deep tissue photoacoustic quantification is established using EGFR positive/negative cell lines and tissue mimicking phantoms.
The DFAC, presented in this study, demonstrates a combination of two complimentary imaging modalities for non-invasive determination of pharmacokinetics and in vivo drug quantification.
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