Chlorin e6 - polyvinylpyrrolidone mediated photosensitization is effective against human non-small cell lung carcinoma compared to small cell lung carcinoma xenografts

Accumulation of oncometabolite D-2-Hydroxyglutarate by SLC25A1 inhibition: A metabolic strategy for induction of HR-ness and radiosensitivity

Oncogenic mutations in metabolic genes and associated oncometabolite accumulation support cancer progression but can also restrict cellular functions needed to cope with DNA damage. For example, gain-of-function mutations in isocitrate dehydrogenase (IDH) and the resulting accumulation of the oncometabolite D-2-hydroxyglutarate (D-2-HG) enhanced the sensitivity of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 and radiotherapy (RT). In our hand, inhibition of the mitochondrial citrate transport protein (SLC25A1) enhanced radiosensitivity of cancer cells and this was associated with increased levels of D-2-HG and a delayed repair of radiation-induced DNA damage. Here we aimed to explore the suggested contribution of D-2-HG-accumulation to disturbance of DNA repair, presumably homologous recombination (HR) repair, and enhanced radiosensitivity of cancer cells with impaired SLC25A1 function. Genetic and pharmacologic inhibition of SLC25A1 (SLC25A1i) increased D-2-HG-levels and sensitized lung cancer and glioblastoma cells to the cytotoxic action of ionizing radiation (IR). SLC25A1i-mediated radiosensitization was abrogated in MEFs with a HR-defect. D-2-HG-accumulation was associated with increased DNA damage and delayed resolution of IR-induced γH2AX and Rad51 foci. Combining SLC25A1i with PARP- or the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs)-inhibitors further potentiated IR-induced DNA damage, delayed DNA repair kinetics resulting in radiosensitization of cancer cells. Importantly, proof of concept experiments revealed that combining SLC25A1i with IR without and with PARPi also reduced tumor growth in the chorioallantoic membrane (CAM) model in vivo. Thereby SLC25A1i offers an innovative strategy for metabolic induction of context-dependent lethality approaches in combination with RT and clinically relevant inhibitors of complementary DNA repair pathways.

Photodynamic therapy of prostate cancer using porphyrinic formulations

Prostate cancer (PCa) is the second most frequent cancer diagnosed in men worldwide. Among the common treatment options, photodynamic therapy (PDT) is being considered a promising local therapy to treat this cancer. Although PDT is an established treatment modality approved for several types of cancer, the low solubility, the reduced tumor selectivity, the absorption in the therapeutic window and the poor clearance from the body of the currently approved photosensitizers (PS) hampers its wide clinical application. In this regard, herein we synthesized three fluorinated porphyrinoid derivatives and entrapped them into polyvinylpyrrolidone (PVP) to prevent their aggregation and preserve their desirable photophysical properties under the physiological environment. In vitro studies revealed the negligible dark cytotoxicity of all PVP formulations (PS1@PVP, PS2@PVP and PS3@PVP) at the tested concentrations (5.0 to 20 μM), but also confirmed the significant photodynamic effect of PS2@PVP and PS3@PVP towards the PCa cell line PC-3, upon red light irradiation at an irradiance of 17.6 mW.cm^-2. To provide insight into the underlying mechanisms of cell death under PDT treatment induced by PS2@PVP and PS3@PVP, their intracellular localization in PC-3 cells was firstly investigated by confocal microscopy. Since both PS2@PVP and PS3@PVP nanoparticles were mainly localized in mitochondria, the involvement of this organelle in PDT-induced apoptosis mediated by both formulations was further explored. Western blot analysis revealed that PDT treatment of PC-3 cells with either PS2@PVP or PS3@PVP resulted in the reduction of the expression level of the anti-apoptotic protein Bcl-2. As the photodamage to Bcl-2 after PDT with PS2@PVP and PS3@PVP was accompanied by the further activation of pro-caspase-3, we assumed that upon irradiation the photogenerated reactive oxygen species (ROS) were able to activate a caspase-dependent apoptotic response as a consequence of a post-mitochondrial event. Taken together, these findings demonstrate that among the tested fluorinated porphyrinoids, PS2@PVP and, particularly, PS3@PVP, are significantly more effective in overall PC-3 cell killing than PS1@PVP, thus highlighting their great potential as therapeutic agents for PCa.

Determination of Optical Properties and Photodynamic Threshold of Lung Tissue for Treatment Planning of In Vivo Lung Perfusion Assisted Photodynamic Therapy

BACKGROUND

Isolated lung metastases in sarcoma and colorectal cancer patients are inadequately treated with current standard therapies. In Vivo Lung Perfusion, a novel platform, could overcome limitations to photodynamic therapy treatment volumes by using low cellular perfusate, removing blood, theoretically allowing greater light penetration. To develop personalized photodynamic therapy protocols requires in silico light propagation simulations based on optical properties and maximal permissible photodynamic threshold dose of lung tissue. This study presents quantification of optical properties for two perfusates and the photodynamic threshold for 5-ALA and Chlorin e6.

METHODS

Porcine and human lungs were placed on Ex Vivo Lung Perfusion, and perfused with acellular solution or blood. Isotropic diffusers were placed within bronchi and on lung surface for light transmission measurements, from which absorption and light scattering properties were calculated at multiple wavelengths. Separately, pigs were injected with 5-ALA or Chlorin e6, and lung tissue was irradiated at increasing doses. Resultant lesion sizes were measured by CT and histology to quantify the photodynamic threshold.

RESULTS

Low cellular perfusate reduced the tissue absorption coefficient significantly, increasing penetration depth of light by 3.3 mm and treatment volumes 3-fold. The photodynamic threshold for lung exposed to 5-ALA was consistent with other malignancies. Chlorin e6 levels were undetectable in lung tissue and did not demonstrate photodynamic-induced necrosis.

CONCLUSIONS

Light penetration with low cellular perfusate is significantly greater and could enable treatments for diffuse disease. This data aids photodynamic treatment planning and will guide clinical translation of photodynamic therapy protocols in the lung, especially during lung perfusion.

Broad-spectrum antibacterial and pro-regenerative effects of photoactivated Photodithazine-Pluronic F127-Chitosan polymer system: In vivo study

Emerging global danger of multidrug resistant microbes makes it essential to explore new approaches to treat infections. We studied antibacterial and pro-regenerative effects of photodynamic therapy (PDT) performed with water solutions of photodithazine and its complexes with Pluronic F127 and chitosan in rat model of full thickness wound (n = 24) infected by an associated Gram-negative and Gram-positive bacteria culture. Laboratory rats were exposed to PDT 24 and 72 h after the injury. Exudate samples were collected before and after PDT for a microbiological study. Autopsy tissues were excised and fixed in formalin on day 4 of the experiment. Fixed tissues were processed and poured into paraffin. Paraffin sections were stained with hematoxylin and eosin and studied by an experienced pathologist. Microbiological analysis revealed that the photoactivation of photodithazine and its complexes suppressed the associated microflora in vivo and inhibited suppurative inflammation in the wounds. The triple Photodithazine-Pluronic F127-Chitosan system possessed the highest antibacterial activity. The morphological study revealed that PDT with photodithazine polymer complexes accelerated wound healing, promoted restoration of microcirculation, facilitated proliferation of fibroblast and vessels and stimulated collagen synthesis. The Photodithazine-Pluronic F127-Chitosan complex may be successfully applied for PDT to prevent and treat suppurative inflammatory diseases of the skin and soft tissues.

Ultrasound-assisted interaction between chlorin-e6 and human serum albumin: pH dependence, singlet oxygen production, and formulation effect

The interaction between chlorin e6 (Ce6) and human serum albumin (HSA) in the presence and absence of ultrasound have been investigated by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy. Ce6 is found to bind strongly to HSA at or near physiological pH conditions, but the strength of the binding is significantly weakened at lower pHs. The intrinsic fluorescence of HSA is incrementally quenched with increasing concentration of Ce6, and the quenching is enhanced after exposure to high-frequency ultrasound. Our experimental results suggest that Ce6-induced sonodynamic oxidation of HSA is mainly mediated by singlet oxygen. The formulation of Ce6 by high molecular weight polyvinylpyrrolidone (PVP) increased its stability in aqueous solutions and its quantum yield of singlet oxygen under ultrasound irradiation.

Nimotuzumab increases the anti-tumor effect of photodynamic therapy in an oral tumor model

Oral squamous cell carcinoma (OSCC) represents 90% of all oral cancers and is characterized with poor prognosis and low survival rate. Epidermal growth factor receptor (EGFR) is highly expressed in oral cancer and is a target for cancer therapy and prevention. In this present work, we evaluate the efficacy of photodynamic therapy (PDT) in combination with an EGFR inhibitor, nimotuzumab in oral cancer cell lines and OSCC xenograft tumor model. PDT is a promising and minimally invasive treatment modality that involves the interaction of a photosensitizer, molecular oxygen and light to destroy tumors. We demonstrated that EGFR inhibitors nimotuzumab and cetuximab exhibits anti-angiogenic properties by inhibiting the migration and invasion of oral cancer cell lines and human endothelial cells. The EGFR inhibitors also significantly reduced tube formation of endothelial cells. Chlorin e6-PDT in combination with nimotuzumab and cetuximab reduced cell proliferation in different oral cancer and endothelial cells. Furthermore, our in vivo studies showed that the combination therapy of PDT and nimotuzumab synergistically delayed tumor growth when compared with control and PDT treated tumors. Downregulation of EGFR, Ki-67 and CD31 was observed in the tumors treated with combination therapy. Analysis of the liver and kidney function markers showed no treatment related toxicity. In conclusion, PDT outcome of oral cancer can be improved when combined with EGFR inhibitor nimotuzumab.

Computer modeling of the complexes of Chlorin e6 with amphiphilic polymers

Recently it has been shown that Chlorin e6 (Ce6) when complexed with Pluronics (hydrophilic ethylene and propylene oxide block copolymers) and poly(N-vinylpyrrolidone) (PVP) exhibits considerably higher phototoxicity towards tumor cells than free Ce6. The present work aimed to model Ce6 interactions with hydrophilic Pluronic F127 and PVP and find out the nature of intermolecular forces stabilizing these complexes. Modeling included 3 steps: (i) application of molecular dynamics to study polymer folding using AMBER 8 program, (ii) evaluation of partial charges in the Ce6 molecule using different quantum mechanical, semi-empirical and topological approaches and (iii) docking analysis of Ce6 interactions with polymer coils using AUTODOCK 4.2. It was found that the folding in regular polymers does not occur stochastically, but involves the formation of "primary" helical structures, which further combined to form hairpin-like "secondary" structures. The latter in turn associated to form coils with minimal solvent accessible hydrophobic area. The Ce6 ring lies flat on the surface of the polymer coil at the interface between hydrophobic and hydrophilic regions. Calculations showed higher affinity of Ce6 for PVP in comparison to Pluronic and revealed marginal contribution of Coulomb forces to the stabilization of both complexes, which are mainly stabilized by van der Waals and hydrogen interactions.

Specific features of early stage of the wound healing process occurring against the background of photodynamic therapy using fotoditazin photosensitizer-amphiphilic polymer complexes

There is a growing demand on the studies of the wound healing potentials of photodynamic therapy. Here we analyze the effects of Fotoditazin, an e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. A skin excision wound model with prevented contraction was developed in male albino rats divided into eight groups according to the treatment mode. All animals received injections of one of the studied compositions into their wound beds and underwent low-intensity laser irradiation or stayed un-irradiated. The clinical monitoring and histological examination of the wounds were performed. It has been found that all the Fotoditazin formulations have significant effects on the early stage of wound healing. The superposition of the inflammation and regeneration was the main difference between groups. The aqueous solution of Fotoditazin alone induced a significant capillary hemorrhage, while its combinations with amphiphilic polymers did not. The best clinical and morphological results were obtained for the Fotoditazin-Pluronic F127 composition. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably, have a great potential for therapy of wounds. Their effects can be attributed to the increased regeneration and suppressed reactions changes at the early stages of repair.

Complexes of Chlorin e6 with Pluronics and Polyvinylpyrrolidone: Structure and Photodynamic Activity in Cell Culture

Polymeric carriers are extensively used in photodynamic therapy (PDT) for increase of efficacy of photosensitizers. Here, we report the influence of nine Pluronic copolymers on phototoxicity of chlorin e6 (Ce6), in particular 5- to 7-fold rise in the phototoxicity caused by hydrophilic Pluronics F127, F108, F68 and F87 and practically no influence on Ce6 of more hydrophobic polymers. The revealed value of 0.2 mg mL(-1) of Pluronic F127 concentration sufficient for half-of-maximal increase of Ce6 photodynamic activity proved to be close to 0.16 mg mL(-1) inherent in well-documented carrier poly(N-vinylpyrrolidone) (PVP). The dissociation constants of Ce6 complexes with Pluronic F127 and PVP that were estimated from UV spectra were 0.252 and 0.036 mg mL(-1) , respectively, indicating higher stability of Ce6 complex with PVP. According to the results of (1) H-NMR studies of Ce6 complexes, the porphyrin interacts not only with hydrophobic regions but also with hydrophilic sides of both polymers.

Protonation-deprotonation equilibria in tetrapyrroles Part 3: Mono- and diprotonations of the trimethyl esters of chlorin e6 and the 71-acetal of rhodin g7 in methanolic hydrochloric acid

Spectrophotometric protonation titrations were performed for the trimethyl esters (TME) of chlorin e6 (31,32-didehydrorhodochlorin-15-acetic acid) and the 71-acetal of rhodin g7 (31,32-didehydrorhodochlorin-71-oxo-15-acetic acid) using HCl as the acid and methanol as the solvent. For rhodin g7 TME, the 71-acetal formation could be clearly detected as the first step in the titration. Only two spectroscopically different protonated species were observed for each chlorin derivative in addition to the neutral forms. The two protonated species were assigned to the monocation and dication of each chlorin derivative. The following p K a values were obtained: p K3 = 4.63 and p K4 = 0.62 for chlorin e6 TME and p K3 = 4.40 and p K4 = 0.60 for the acetal of rhodin g7 TME. The protonation titration for chlorin e6 TME with HCl in acetic acid afforded UV-vis spectra similar to those obtained with HCl in methanol. The UV-vis spectrometric parameters are given for the neutral forms of chlorin e6 TME, rhodin g7 TME and its 71-acetal, as well as for the mono- and diprotonated species of chlorin e6 TME and rhodin g7 TME acetal. The protonation titration results of the chlorin e6 derivatives are compared with those previously obtained for phytyl/methyl pyropheophorbide a.

Oxidative stress effects of fullerene-porphyrin derivatives in photodynamic therapy

Due to their special and growing medical recent interest, the fullerenes started to be a very studied class of chemical compounds. In order to improve their water solubility and to reduce their cytotoxic characteristics, the fullerenes have been coupled in a system fullerene/PVP/porphyrin (C60/PVP/TPP) and its application in photodynamic therapy will be evaluated in this paper. The oxidative stress effects on photodynamic therapy with systems fullerene/poly-N-vinylpirrolidone/5,10,15,20-tetrakis(4-phenyl)porphyrin (C60/PVP/TPP) were tested on Wistar rats sub-cutaneously inoculated with Walker 256 carcinoma. The animals were irradiated with red light (λ = 685 nm; D = 50 J/cm2; 15 minutes) 24 h after intra-peritoneal administration of 10 mg/kg body weight of the system C60/PVP/TPP. After photodynamic therapy, the free radicals in tumors have been indirectly evaluated by lipid peroxides level (measured as thiobarbituric reactive substances) and protein carbonyls (indices of oxidative effects produced on susceptible biomolecules), both of them increasing in tumor tissues of animals 24 h after treatment. The levels of thiol groups and total antioxidant capacity have been determined in tumors, too, their decreasing values being the effect of the strong tumoral oxidative process.

Assembly of aptamer switch probes and photosensitizer on gold nanorods for targeted photothermal and photodynamic cancer therapy

An aptamer switch probe (ASP) linking chlorin e6 (Ce6), a photosensitizer molecule, to the surface of gold nanorods (AuNRs) was used to target cancer cells for photodynamic therapy (PDT) and photothermal therapy (PTT). In the presence of target cancer cells, the ASP changes conformation to drive Ce6 away from the gold surface, thereby producing singlet oxygen for PDT upon light irradiation. Since each AuNR is modified with many ASP-Ce6 molecules, the AuNR-ASP-Ce6 conjugate yields enhanced binding and therapeutic effect by the added ability to carry many photosensitizers. In addition, absorption of radiation by the gold nanorods enables further cell destruction by the photothermal effect. Consequently, this multimodal AuNR-ASP-Ce6 conjugate offers a remarkably improved and synergistic therapeutic effect compared to PTT or PDT alone, providing high specificity and therapeutic efficiency, which can be generalized to other types of cancer therapies.

Role of elevated pressure in TRAIL-induced apoptosis in human lung carcinoma cells

TNF-related apoptosis-inducing ligand (TRAIL, Apo2L) is a promising anticancer agent with high specificity for cancer cells. Many strategies have been proposed to enhance the sensitivity of cancer cells to TRAIL-mediated apoptosis, including the use of combination treatment with conventional cancer therapies. However, few reports have evaluated the effects of TRAIL in combination with mechanical stress, which can also cause apoptosis of cancer cells. In the present study, we describe a custom-designed culture system that delivers two atmospheres of elevated pressure (EP) by using compressed air, and which enhances the sensitivity of cancer cells to TRAIL-mediated apoptosis. The combination of TRAIL and EP significantly increased apoptosis of human H460 lung cancer cells more than hyperbaric normoxia or normobaric mild hyperoxia. EP-potentiating TRAIL-mediated apoptosis of H460 cells was accompanied by up-regulated death receptor 5 (DR5), activation of caspases, decreased mitochondrial membrane potential, and reactive oxygen species production. We also observed EP-induced sensitization of TRAIL-mediated apoptosis in other cancer cell types. In contrast, human normal cells showed no DNA damage or cell death when exposed to the combined treatment. In a chicken chorioallantoic membrane model, EP enhanced TRAIL-mediated apoptosis of tumors that developed from transplanted H460 cells. Collectively, EP enhanced TRAIL-induced apoptosis of human lung carcinoma cells in vitro and in vivo. These findings suggest that EP is a mechanical and physiological stimulus that might have utility as a sensitizing tool for cancer therapy.

Chlorin e6-polyvinylpyrrolidone mediated photodynamic therapy--A potential bladder sparing option for high risk non-muscle invasive bladder cancer

BACKGROUND

Bladder sparing treatment options for high risk non-muscle invasive blader cancer (NMIBC) after intravesical Bacillus Calmette-Guerin (BCG) failure are limited.

OBJECTIVE

To evaluate photodynamic therapy (PDT) using chlorin e6-polyvinylpyrrolidone (Ce6-PVP) as a bladder sparing therapy for NMIBC refractory to intravesical BCG therapy.

MATERIALS AND METHODS

Between July 2004 and June 2009, patients with recurrent NMIBC after induction intravesical BCG therapy were treated with PDT performed with a 665nm laser and light dosimetry of 10-24J/cm(2). The patients underwent cystoscopic surveillance for tumour recurrence post PDT. Post treatment lower urinary tract symptoms and bladder capacity were also monitored. Serum and urine samples were collected for spectrometric quantification of photosensitizer levels.

RESULTS

Five patients underwent PDT, with a total of seven treatments performed. One patient received intravenous Ce6-PVP, while the rest received intravesical Ce6-PVP.The median age was 80 years (mean 79 years, range 72-88 years). There were three patients with primary CIS of the bladder and two with T1 high grade TCC and CIS of the bladder. At a median follow-up of 29 months (mean 25 months, range 6-36 months), two patients were disease free, two patients developed recurrence and one patient progressed to muscle invasive disease. There were no immediate adverse effects. The patient receiving intravenous Ce6-PVP developed an enterovesical fistula 16 months post PDT.

CONCLUSIONS

Despite being a small pilot study, intravesical Ce6-PVP mediated PDT is a feasible bladder sparing treatment option for recurrent high risk non-muscle invasive bladder carcinoma in selected individuals.

Bifunctional agents for imaging and therapy

Multiple, complementary techniques for tumor detection, including magnetic resonance, nuclear and optical imaging, are under active development; each approach has particular strengths and advantages. Efforts are also currently underway to develop bifunctional agents, so that a single molecule can be used for imaging, therapy, and monitoring the long-term tumor response. This chapter is mainly focused on illustrating the utility of certain tumor-avid photosensitizers in developing agents for tumor imaging [fluorescence, magnetic resonance imaging (MRI), positron emission tomography (PET)] and photodynamic therapy. Recent approaches for developing target-specific agents for photodynamic therapy (PDT) and in vivo tumor imaging are also briefly discussed.

Screening of nanoparticulate delivery systems for the photodetection of cancer in a simple and cost-effective model

AIMS

In urology, fluorescence-based imaging methods have been proven to significantly improve the detection of small, barely visible tumors and reduce the recurrence rate. Under ethical and economical pressure, new effective screening systems have to be developed to exploit and assess novel strategies for fluorescence photodetection in other areas. For this purpose, the chorioallantoic membrane (CAM) of the developing chick embryo is an attractive alternative model to the mammalian models.

MATERIALS & METHODS

Hypericin encapsulated into nanoparticles for the photodetection of ovarian metastases was evaluated in the CAM model with respect to vascular extravazation and tumor targeting and compared with free drug following intravenous administration.

RESULTS

To validate the CAM model as a valuable screening system for photodetection of cancer, we drew a comparison with results obtained on a conventional rodent model.

CONCLUSION

Rodent and CAM models led to the same conclusion regarding the benefits of nanoencapsulation to improve selective accumulation of drug in ovarian micrometastases.

In-vivo optical detection of cancer using chlorin e6--polyvinylpyrrolidone induced fluorescence imaging and spectroscopy

Background

Photosensitizer based fluorescence imaging and spectroscopy is fast becoming a promising approach for cancer detection. The purpose of this study was to examine the use of the photosensitizer chlorin e6 (Ce6) formulated in polyvinylpyrrolidone (PVP) as a potential exogenous fluorophore for fluorescence imaging and spectroscopic detection of human cancer tissue xenografted in preclinical models as well as in a patient.

Methods

Fluorescence imaging was performed on MGH human bladder tumor xenografted on both the chick chorioallantoic membrane (CAM) and the murine model using a fluorescence endoscopy imaging system. In addition, fiber optic based fluorescence spectroscopy was performed on tumors and various normal organs in the same mice to validate the macroscopic images. In one patient, fluorescence imaging was performed on angiosarcoma lesions and normal skin in conjunction with fluorescence spectroscopy to validate Ce6-PVP induced fluorescence visual assessment of the lesions.

Results

Margins of tumor xenografts in the CAM model were clearly outlined under fluorescence imaging. Ce6-PVP-induced fluorescence imaging yielded a specificity of 83% on the CAM model. In mice, fluorescence intensity of Ce6-PVP was higher in bladder tumor compared to adjacent muscle and normal bladder. Clinical results confirmed that fluorescence imaging clearly captured the fluorescence of Ce6-PVP in angiosarcoma lesions and good correlation was found between fluorescence imaging and spectral measurement in the patient.

Conclusion

Combination of Ce6-PVP induced fluorescence imaging and spectroscopy could allow for optical detection and discrimination between cancer and the surrounding normal tissues. Ce6-PVP seems to be a promising fluorophore for fluorescence diagnosis of cancer.

Membrane transport enhancement of chlorin e6-polyvinylpyrrolidone and its photodynamic efficacy on the chick chorioallantoic model

We have determined the influences of polyvinylpyrrolidone (PVP) on the topical delivery of chlorin e6 (Ce6) in malignant bladder cells. The chick chorioallantoic membrane (CAM) was used to model the tumor spheroids that resemble small residual bladder tumors prior to vascularization. Macroscopic fluorescence imaging showed that Ce6-PVP-induced fluorescence had a higher sensitivity and specificity for delineating tumor from the adjacent normal CAM compared to Ce6 alone. Nonlinear regression analyses have shown that Ce6-PVP has a longer half-life in the tumor compared to Ce6. The uptake ratio of Ce6-PVP was found to have a 2-fold increase across the CAM when compared to that of Ce6, indicating that PVP was able to facilitate diffusion of Ce6 across the membrane. Confocal laser scanning microscopy further confirmed that Ce6-PVP has better penetration in the CAM as well as in the tumor cells compared to Ce6. The present work contributes to our understanding of the Ce6-PVP drug-polymer system by demonstrating for the first time that the presence of PVP facilitates the transport of Ce6 across the chorioallantoic membrane.

In vitro survival of nonsmall cell lung cancer cells following combined treatment with ionizing radiation and photofrin-mediated photodynamic therapy

It has been suggested that combination high dose rate (HDR) intraluminal brachytherapy and photodynamic therapy (PDT) in nonsmall cell lung cancer (NSCLC) may improve efficacy of treatment, reduce toxicity and enhance quality of life for patients. To provide a cellular basis for this we examined the in vitro sensitivity of MRC5 normal lung fibroblasts and four NSCLC cell lines following HDR radiation, PDT and combined HDR radiation and PDT. HDR radiation was cobalt-60 gamma rays (1.5-1.9 Gy min(-1)). For PDT treatment, cells were exposed to 2.5 microg mL(-1) Photofrin for 18-24 h followed by light exposure (20 mW cm(-2)). For combined treatment cells were exposed to Photofrin and then either exposed to light and 15-30 min later exposed to HDR radiation or exposed to HDR radiation and 15-30 min later exposed to light. D(37) values calculated from clonogenic survival curves indicated a six-fold difference in HDR radiation sensitivity and an eight-fold difference in PDT sensitivity. The effect of combined treatment was not significantly different from an additive effect of the individual treatment modalities for the NSCLC cells, but was significantly less than additive for the MRC5 cells. These results suggest an equivalent tumor cell kill may be possible at reduced systemic effects to patients.