Photodynamic therapy (PDT), a spatially localized phototoxic therapy that involves irradiation of a photosensitizer (PS) with specific wavelengths of light, has shown exceptional promise in impacting cancer treatment outcomes, particularly oral cancer. To reduce PDT outcome variability, attempts toward image-guided personalized PDT are being pursued by monitoring PS uptake either via fluorescence or photoacoustic imaging (PAI), a nonionizing modality dependent on optical absorption properties of the tissue. PAI-guided PDT requires a near-infrared contrast agent for deep tissue imaging with minimal photobleaching effect. We evaluate the impact of PDT agent, benzoporphyrin derivative (BPD), on PAI agent indocyanine green (ICG) and vice versa, given that they have different optical absorption properties and singlet oxygen quantum yields for PDT. Specifically, we demonstrate in two oral squamous cell carcinoma lines (FaDu and SCC4) that ICG has minimal effect on BPD PDT efficacy when irradiated with either a continuous or pulsed laser. Furthermore, the impact of BPD on ICG photodegradation was monitored with PAI in tissue-mimicking phantoms. These studies inform us that the combination of BPD and ICG can be utilized for PAI-guided PDT. However, researchers need to consider the photodegradation effects of ICG in the presence of BPD when designing their drug delivery strategies for PAI-guided PDT.
Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease marked by poor response to virtually all available treatments. Clinical trials of chemo, targeted therapies, and radiation, have resulted in minimal advances, and survival after diagnosis is generally less than a year. In the pursuit of new avenues for therapeutic development for this lethal disease, a number of studies have implicated the role of tumor-promoting microRNAs with altered expression PDAC tissues. Here, using in vitro 3D organoids we explore the strategy of combining photodynamic therapy (PDT) with a novel microRNA therapeutic platform to target miR21, an established onco-miR that targets multiple tumor suppressors. This approach is motivated by recent clinical studies establishing the technical feasibility of light delivery to the pancreas, combined by evidence that PDT may disrupt or loosen stroma and potentially increase delivery of anti-miR agents. To evaluate this hypothesis, we use in vitro co-culture models of PDAC cells and stromal fibroblasts that recapitulate the dense fibrotic stroma of PDAC tumors to evaluate response to treatment in verteporfin PDT and anti-miR combination and monotherapy treatment arms. Using stably-transfected miR-21 sponge expressing we also perform mechanistic studies to investigate the role of miR 21 in response to PDT and chemotherapy in 3D cultures with and without stromal partners.
We report the use of digital holographic microscopy (DHM) as a viable microscopy approach for quantitative, nondestructive longitudinal imaging of in vitro three-dimensional (3-D) tumor models. Following established methods, we prepared 3-D cultures of pancreatic cancer cells in overlay geometry on extracellular matrix beds and obtained digital holograms at multiple time points throughout the duration of growth. The holograms were digitally processed and the unwrapped phase images were obtained to quantify the nodule thickness over time under normal growth and in cultures subject to chemotherapy treatment. In this manner, total nodule volumes are rapidly estimated and demonstrated here to show contrasting time-dependent changes during growth and in response to treatment. This work suggests the utility of DHM to quantify changes in 3-D structure over time and suggests the further development of this approach for time-lapse monitoring of 3-D morphological changes during growth and in response to treatment that would otherwise be impractical to visualize.
KEYWORDS: Digital holography, 3D modeling, Microscopy, Holography, Tumors, 3D image processing, Time lapse microscopy, Holographic interferometry, Tumor growth modeling, Digital color imaging
While three-dimensional tumor models have emerged as valuable tools in cancer research, the ability to longitudinally visualize the 3D tumor architecture restored by these systems is limited with microscopy techniques that provide only qualitative insight into sample depth, or which require terminal fixation for depth-resolved 3D imaging. Here we report the use of digital holographic microscopy (DHM) as a viable microscopy approach for quantitative, non-destructive longitudinal imaging of in vitro 3D tumor models. Following established methods we prepared 3D cultures of pancreatic cancer cells in overlay geometry on extracellular matrix beds and obtained digital holograms at multiple timepoints throughout the duration of growth. The holograms were digitally processed and the unwrapped phase images were obtained to quantify nodule thickness over time under normal growth, and in cultures subject to chemotherapy treatment. In this manner total nodule volumes are rapidly estimated and demonstrated here to show contrasting time dependent changes during growth and in response to treatment. This work suggests the utility of DHM to quantify changes in 3D structure over time and suggests the further development of this approach for time-lapse monitoring of 3D morphological changes during growth and in response to treatment that would otherwise be impractical to visualize.
The dismal survival statistics for pancreatic cancer are due in large part to the notoriously poor response of these tumors
to conventional therapies. Here we examine the ability of photodynamic therapy (PDT), using the photosensitizer
verteporfin to enhance of the efficacy of traditional chemotherapy agents and/or eradicate populations that are nonresponsive
to these agents. Using an in vitro 3D tumor model of pancreatic cancer combined with an imaging-based
methodology for quantifying therapeutic response, we specifically examine PDT combination treatments with
gemcitabine and oxaliplatin. We show that our 3D cell culture model recapitulates a more clinically-relevant dose
response to gemcitabine, with minimal cytotoxic response even at high doses. The same cultures exhibit modest response
to PDT treatments, but are also less responsive to this modality relative to our previous reports of monolayer dose
response in the same cells. In combination we found no evidence of any enhancement in efficacy of either PDT or
gemcitabine treatment regardless of dose or sequence (PDT before gemcitabine, or gemcitabine before PDT). However,
when oxaliplatin chemotherapy was administered immediately after treatment with 2.5J/cm2 verteporfin PDT, there was
an observable enhancement in response that appears to exceed the additive combination of either treatment alone and
suggesting there may be a synergistic interaction. This observation is consistent with previous reports of enhanced
efficacy in combinations of PDT with platinum-based chemotherapy. The contrast in results between the combinations
examined here underscores the need for rational design of mechanism-based PDT combinations.
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