Search tips
Search criteria

Results 1-15 (15)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  A Method for Choosing the Smoothing Parameter in a Semi-parametric Model for Detecting Change-points in Blood Flow 
Journal of applied statistics  2013;41(1):26-45.
In a smoothing spline model with unknown change-points, the choice of the smoothing parameter strongly influences the estimation of the change-point locations, and the function at the change-points. In a tumor biology example, where change-points in blood flow in response to treatment were of interest, choosing the smoothing parameter based on minimizing generalized cross validation, GCV, gave unsatisfactory estimates of the change-points. We propose a new method, aGCV, that re-weights the residual sum of squares and generalized degrees of freedom terms from GCV. The weight is chosen to maximize the decrease in the generalized degrees of freedom as a function of the weight value, while simultaneously minimizing aGCV as a function of the smoothing parameter and the change-points. Compared to GCV, simulation studies suggest that the aGCV method yields improved estimates of the change-point and the value of the function at the change-point.
PMCID: PMC3896242  PMID: 24459325
Change-points; Smoothing spline; Partial spline; Generalized Cross Validation; Generalized Degrees of Freedom
2.  Photodynamic Therapy of Disseminated Non-Small Cell Lung Carcinoma in a Murine Model 
Lasers in surgery and medicine  2011;43(7):663-675.
Background and Objective
Photodynamic therapy (PDT) of thoracic malignancies involving the pleural surfaces is an active area of clinical investigation. The present report aims to characterize a model for PDT of disseminated non-small cell lung carcinoma grown orthotopically in nude mice, and to evaluate PDT effect on tumor and normal tissues.
Study Design
H460 human non-small cell lung carcinoma (NSCLC) cells were injected percutaneously into the thoracic cavity of nude mice. HPPH-PDT (1 mg/kg, 24 h) was performed via the interstitial delivery (150 mW/cm) of 661 nm light to the thoracic cavity at fluences of 25-200 J/cm.
H460 tumors exhibited exponential growth within the thoracic cavity consisting of diffuse, gross nodular disease within 9 days after intrathoracic injection. Tumor volume, measured by magnetic resonance imaging (MRI), was highly correlated with the aggregate tumor mass extracted from the corresponding animal. Intrathoracic PDT at fluences of ≥ 50 J/cm produced significant decreases in tumor burden as compared to untreated controls, however mortality increased with rising fluence. Accordingly, 50 J/cm was selected for MRI studies to measure intra-animal PDT effects. Tumor distribution favored the ventral (vs. dorsal), caudal (vs. cranial), and right (vs. left) sides of the thoracic cavity by MRI; PDT did not change this spatial pattern despite an overall effect on tumor burden. Histopathology revealed edema and fibrin deposition within the pulmonary interstitium and alveoli of the PDT-treated thoracic cavity, as well as occasional evidence of vascular disruption. Prominent neutrophil infiltration with a concomitant decline in the lymphocyte compartment was also noted in the lung parenchyma within 24 hours after PDT.
HPPH-PDT of an orthotopic model of disseminated NSCLC is both feasible and effective using intracavitary light delivery. We establish this animal model, together with the treatment and monitoring approaches, as novel and valuable methods for the pre-clinical investigation of intrathoracic PDT of disseminated pleural malignancies.
PMCID: PMC3676899  PMID: 22057494
HPPH; Photochlor®; 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a; interstitial illumination; magnetic resonance imaging; non-small cell lung carcinoma; photodynamic therapy; pleural malignancy
3.  Tumor Vascular Microenvironment Determines Responsiveness to Photodynamic Therapy 
Cancer Research  2012;72(8):2079-2088.
The efficacy of photodynamic therapy (PDT) depends upon the delivery of both photosensitizing drug and oxygen. In this study, we hypothesized that local vascular microenvironment is a determinant of tumor response to PDT. Tumor vascularization and its basement membrane (collagen) were studied as a function of supplementation with basement membrane matrix (Matrigel) at the time of tumor cell inoculation. Effects on vascular composition with consequences to tumor hypoxia, photosensitizer uptake and PDT response were measured. Matrigel-supplemented tumors developed more normalized vasculature, composed of smaller and more uniformly-spaced blood vessels than their unsupplemented counterparts, but these changes did not affect tumor oxygenation or PDT-mediated direct cytotoxicity. However, PDT-induced vascular damage increased in Matrigel-supplemented tumors, following an affinity of the photosensitizer Photofrin for collagen-containing vascular basement membrane coupled with increased collagen content in these tumors. The more highly-collagenated tumors demonstrated more vascular congestion and ischemia after PDT, along with a higher probability of curative outcome that was collagen dependent. In the presence of photosensitizer-collagen localization, PDT effects on collagen were evidenced by a decrease in its association with vessels. Together, our findings demonstrate that photosensitizer localization to collagen increases vascular damage and improves treatment efficacy in tumors with greater collagen content. The vascular basement membrane is thus identified to be a determinant of therapeutic outcome in PDT of tumors.
PMCID: PMC3328659  PMID: 22374982
collagen; photodynamic therapy; microenvironment; normalization; vasculature
4.  Fluence Rate-Dependent Intratumor Heterogeneity in Physiologic and Cytotoxic Responses to Photofrin Photodynamic Therapy 
Photodynamic therapy (PDT) can lead to the creation of heterogeneous, response-limiting hypoxia during illumination, which may be controlled in part through illumination fluence rate. In the present report we consider 1) regional differences in hypoxia, vascular response, and cell kill as a function of tumor depth and 2) the role of fluence rate as a mediator of depth-dependent regional intratumor heterogeneity. Intradermal RIF murine tumors were treated with Photofrin-PDT using surface illumination at an irradiance of 75 or 38 mW/cm2. Regional heterogeneity in tumor response was examined through comparison of effects in the surface vs. base of tumors, i.e. along a plane parallel to the skin surface and perpendicular to the incident illumination. 75 mW/cm2-PDT created significantly greater hypoxia in tumor bases relative to their surfaces. Increased hypoxia in the tumor base could not be attributed to regional differences in Photofrin concentration nor effects of fluence rate distribution on photochemical oxygen consumption, but significant depth-dependent heterogeneity in vascular responses and cytotoxic response were detected. At a lower fluence rate of 38 mW/cm2, no detectable regional differences in hypoxia or cytotoxic responses were apparent, and heterogeneity in vascular response was significantly less than that during 75 mW/cm2-PDT. This research suggests that the benefits of low-fluence-rate-PDT are mediated in part by a reduction in intratumor heterogeneity in hypoxic, vascular and cytotoxic responses.
PMCID: PMC2834171  PMID: 20024165
photodynamic therapy; fluence rate; hypoxia; EF3; blood flow
5.  Motexafin lutetium-photodynamic therapy of prostate cancer: Short and long term effects on PSA 
The time course of serum PSA response to photodynamic therapy (PDT) of prostate cancer was measured.
Experimental Design:
Seventeen patients were treated in a Phase I trial of motexafin lutetium-PDT. PDT dose was calculated in each patient as the product of the ex vivo-measured pre-PDT photosensitizer level and the in situ-measured light dose. Serum PSA level was measured within two months prior to PDT (baseline), and at day 1; weeks 1-3; months 1, 2 and 3; months 4-6 and months 7-11 after PDT.
At 24h after PDT, serum PSA increased by 98±36% (mean ± SE) relative to baseline levels (p=0.007). When patients were dichotomized based on median PDT dose, those who received high PDT dose demonstrated a 119±52% increase in PSA compared to a 54±27% increase in patients treated at low PDT dose. Patients treated with high vs. low PDT dose demonstrated a median biochemical delay of 82 vs. 43 days (p=0.024), with biochemical delay defined as the length of time between PDT and a nonreversible increase in PSA to a value ≥baseline.
Results show PDT to induce large, transient increases in serum PSA levels. Patients who experienced high PDT dose demonstrated greater short-term increase in PSA and a significantly more durable PSA response (biochemical delay). These data strongly promote the need for individualized delivery of PDT dose and assessment of treatment effect in PDT of prostate cancer. Information gained from such patient-specific measurements could facilitate the introduction of multiple PDT sessions in patients who would benefit.
PMCID: PMC2680073  PMID: 18676760
motexafin lutetium; prostate; PSA; PDT dose; photosensitizer concentration
6.  Photodynamic therapy activated signaling from epidermal growth factor receptor and STAT3 
Cancer Biology & Therapy  2012;13(14):1463-1470.
Patients with serosal (pleural or peritoneal) spread of malignancy have few definitive treatment options and consequently have a very poor prognosis. We have previously shown that photodynamic therapy (PDT) can be an effective treatment for these patients, but that the therapeutic index is relatively narrow. Here, we test the hypothesis that EGFR and STAT3 activation increase survival following PDT, and that inhibiting these pathways leads to increased PDT-mediated direct cellular cytotoxicity by examining BPD-PDT in OvCa and NSCLC cells. We found that BPD-mediated PDT stimulated EGFR tyrosine phosphorylation and nuclear translocation, and that EGFR inhibition by erlotinib resulted in reduction of PDT-mediated EGFR activation and nuclear translocation. Nuclear translocation and PDT-mediated activation of EGFR were also observed in response to BPD-mediated PDT in multiple cell lines, including OvCa, NSCLC and head and neck cancer cells, and was observed to occur in response to porfimer sodium-mediated PDT. In addition, we found that PDT stimulates nuclear translocation of STAT3 and STAT3/EGFR association and that inhibiting STAT3 signaling prior to PDT leads to increased PDT cytotoxicity. Finally, we found that inhibition of EGFR signaling leads to increased PDT cytotoxicity through a mechanism that involves increased apoptotic cell death. Taken together, these results demonstrate that PDT stimulates the nuclear accumulation of both EGFR and STAT3 and that targeting these survival pathways is a potentially promising strategy that could be adapted for clinical trials of PDT for patients with serosal spread of malignancy.
PMCID: PMC3542238  PMID: 22986230
PDT; EGFR; STAT3; lung cancer; ovarian cancer; pleural; peritoneal
7.  Two New “Protected” Oxyphors for Biological Oximetry: Properties and Application in Tumor Imaging 
Analytical chemistry  2011;83(22):8756-8765.
We report the synthesis, calibration, and examples of application of two new phosphorescent probes, Oxyphor R4 and Oxyphor G4, optimized specifically for in vivo oxygen imaging by phosphorescence quenching. These “protected” dendritic probes can operate in either albumin-rich (blood plasma) or albumin-free (interstitial space) environments at all physiological oxygen concentrations, from normoxic to deep hypoxic conditions. Oxyphors R4 and G4 are derived from phosphorescent Pd-meso-tetra-(3,5-dicarboxyphenyl)-porphyrin (PdP) or Pd-meso-tetra-(3,5-dicarboxyphenyl)-tetrabenzoporphyrin (PdTBP), respectively, and possess features common for protected dendritic probes, i.e., hydrophobic dendritic encapsulation of phosphorescent metalloporphyrins and hydrophilic PEGylated periphery. The new Oxyphors are highly soluble in aqueous environments and do not permeate biological membranes. The probes were calibrated under physiological conditions (pH 6.4–7.8) and temperatures (22–38 °C), showing high stability, reproducibility of signals, and lack of interactions with biological solutes. Oxyphor G4 was used to dynamically image intravascular and interstitial oxygenation in murine tumors in vivo. The physiological relevance of the measurements was demonstrated by dynamically recording changes in tissue oxygenation during application of anesthesia (isofluorane). These experiments revealed that changes in isofluorane concentration significantly affect tissue oxygenation.
PMCID: PMC3617485  PMID: 21961699
8.  Radiation mitigating properties of the lignan component in flaxseed 
BMC Cancer  2013;13:179.
Wholegrain flaxseed (FS), and its lignan component (FLC) consisting mainly of secoisolariciresinol diglucoside (SDG), have potent lung radioprotective properties while not abrogating the efficacy of radiotherapy. However, while the whole grain was recently shown to also have potent mitigating properties in a thoracic radiation pneumonopathy model, the bioactive component in the grain responsible for the mitigation of lung damage was never identified. Lungs may be exposed to radiation therapeutically for thoracic malignancies or incidentally following detonation of a radiological dispersion device. This could potentially lead to pulmonary inflammation, oxidative tissue injury, and fibrosis. This study aimed to evaluate the radiation mitigating effects of FLC in a mouse model of radiation pneumonopathy.
We evaluated FLC-supplemented diets containing SDG lignan levels comparable to those in 10% and 20% whole grain diets. 10% or 20% FLC diets as compared to an isocaloric control diet (0% FLC) were given to mice (C57/BL6) (n=15-30 mice/group) at 24, 48, or 72-hours after single-dose (13.5 Gy) thoracic x-ray treatment (XRT). Mice were evaluated 4 months post-XRT for blood oxygenation, lung inflammation, fibrosis, cytokine and oxidative damage levels, and survival.
FLC significantly mitigated radiation-related animal death. Specifically, mice fed 0% FLC demonstrated 36.7% survival 4 months post-XRT compared to 60–73.3% survival in mice fed 10%-20% FLC initiated 24–72 hours post-XRT. FLC also mitigated radiation-induced lung fibrosis whereby 10% FLC initiated 24-hours post-XRT significantly decreased fibrosis as compared to mice fed control diet while the corresponding TGF-beta1 levels detected immunohistochemically were also decreased. Additionally, 10-20% FLC initiated at any time point post radiation exposure, mitigated radiation-induced lung injury evidenced by decreased bronchoalveolar lavage (BAL) protein and inflammatory cytokine/chemokine release at 16 weeks post-XRT. Importantly, neutrophilic and overall inflammatory cell infiltrate in airways and levels of nitrotyrosine and malondialdehyde (protein and lipid oxidation, respectively) were also mitigated by the lignan diet.
Dietary FLC given early post-XRT mitigated radiation effects by decreasing inflammation, lung injury and eventual fibrosis while improving survival. FLC may be a useful agent, mitigating adverse effects of radiation in individuals exposed to incidental radiation, inhaled radioisotopes or even after the initiation of radiation therapy to treat malignancy.
PMCID: PMC3636021  PMID: 23557217
Flaxseed lignan complex; Radiation pneumonopathy; Radiation dispersion device; Mitigation; Lung fibrosis; Antioxidant; Nitrotyrosine; TBARS; TGF-beta 1; SDG; SARRP; ROS
9.  Evaluation of phototoxicity of dendritic porphyrin-based phosphorescent oxygen probes: an in vitro study† 
Biological oxygen measurements by phosphorescence quenching make use of exogenous phosphorescent probes, which are introduced directly into the medium of interest (e.g. blood or interstitial fluid) where they serve as molecular sensors for oxygen. The byproduct of the quenching reaction is singlet oxygen, a highly reactive species capable of damaging biological tissue. Consequently, potential probe phototoxicity is a concern for biological applications. Herein, we compared the ability of polyethyleneglycol (PEG)-coated Pd tetrabenzoporphyrin (PdTBP)-based dendritic nanoprobes of three successive generations to sensitize singlet oxygen. It was found that the size of the dendrimer has practically no effect on the singlet oxygen sensitization efficiency in spite of the strong attenuation of the triplet quenching rate with an increase in the dendrimer generation. This unexpected result is due to the fact that the lifetime of the PdTBP triplet state in the absence of oxygen increases with dendritic generation, thus compensating for the concomitant decrease in the rate of quenching. Nevertheless, in spite of their ability to sensitize singlet oxygen, the phosphorescent probes were found to be non-phototoxic when compared with the commonly used photodynamic drug Photofrin in a standard cell-survival assay. The lack of phototoxicity is presumably due to the inability of PEGylated probes to associate with cell surfaces and/or penetrate cellular membranes. In contrast, conventional photosensitizers bind to cell components and act by generating singlet oxygen inside or in the immediate vicinity of cellular organelles. Therefore, PEGylated dendritic probes are safe to use for tissue oxygen measurements as long as the light doses are less than or equal to those commonly employed in photodynamic therapy.
PMCID: PMC3607943  PMID: 21409208
10.  Photodynamic Therapy in the Management of Pre-Malignant Head and Neck Mucosal Dysplasia and Microinvasive Carcinoma 
The management of head and neck mucosal dysplasia and microinvasive carcinoma is an appealing strategy to prevent the development of invasive carcinomas. While surgery remains the standard of care, photodynamic therapy (PDT) offers several advantages including the ability to provide superficial yet wide field mucosal ablative treatment. This is particularly attractive where defining the extent of the dysplasia can be difficult. PDT can also retreat the mucosa without any cumulative fibrotic complications affecting function. To date, clinical experience suggests that this treatment approach can be effective in obtaining a complete response for the treated lesion but long term follow-up is limited. Further research efforts are needed to define not only the risk of malignant transformation with PDT but to develop site specific treatment recommendations that include the fluence, fluence rate and light delivery technique.
PMCID: PMC3598575  PMID: 21497298
head and neck premalignant dysplasia; microinvasive carcinoma; photodynamic therapy; PDT; review
11.  Interference with the Jaffé Method for Creatinine Following 5-Aminolevulinic Acid Administration 
The photosensitizer pro-drug 5-aminolevulinic acid (5-ALA) has been administered systemically for photodynamic therapy. Although several toxicities have been reported, nephrotoxicity has never been observed.
Materials and Methods
Patients with head and neck mucosal dysplasia have been treated on a phase 1 study of escalating light doses in combination with 60 mg/kg of oral 5-ALA. Serum creatinine was measured with the modified Jaffe method or an enzymatic method in the first 24 hours after 5-ALA. Interference by 5-ALA, as well as by its photosensitizing product protoporphyrin IX, was assessed.
Among 11 subjects enrolled to date, 9 of 11 had blood chemistries collected within the first 5 hours with 7 demonstrating significant grade 3 creatinine elevations (p=0.030). There was no additional evidence of compromised renal function or increased PDT-induced mucositis. Creatinine levels measured by the Jaffe assay increased linearly as a function of the ex-vivo addition of ALA (p<.0001). The exogenous addition of PpIX did not alter creatinine levels. ALA did not interfere with creatinine levels as measured by an enzymatic assay. A total of 4 of the 11 subjects had creatinine levels prospectively measured by both the Jaffe and the enzymatic assays. Only the Jaffe method demonstrated significant elevations as a function of time after ALA administration.
The transient increase in creatinine after systematic ALA can be attributed, in part, if not entirely, to interference of ALA in the Jaffe reaction. Alternative assays should be employed in situations calling for monitoring of kidney function after systemic ALA.
PMCID: PMC3598580  PMID: 21112550
Levulan; photodynamic therapy; side-effect; creatinine; Jaffe method
12.  Tumor Blood Flow Differs between Mouse Strains: Consequences for Vasoresponse to Photodynamic Therapy 
PLoS ONE  2012;7(5):e37322.
Fluctuations in tumor blood flow are common and attributed to factors such as vasomotion or local vascular structure, yet, because vessel structure and physiology are host-derived, animal strain of tumor propagation may further determine blood flow characteristics. In the present report, baseline and stress-altered tumor hemodynamics as a function of murine strain were studied using radiation-induced fibrosacomas (RIF) grown in C3H or nude mice. Fluctuations in tumor blood flow during one hour of baseline monitoring or during vascular stress induced by photodynamic therapy (PDT) were measured by diffuse correlation spectroscopy. Baseline monitoring revealed fluctuating tumor blood flow highly correlated with heart rate and with similar median periods (i.e., ∼9 and 14 min in C3H and nudes, respectively). However, tumor blood flow in C3H animals was more sensitive to physiologic or stress-induced perturbations. Specifically, PDT-induced vascular insults produced greater decreases in blood flow in the tumors of C3H versus nude mice; similarly, during baseline monitoring, fluctuations in blood flow were more regular and more prevalent within the tumors of C3H mice versus nude mice; finally, the vasoconstrictor L-NNA reduced tumor blood flow in C3H mice but did not affect tumor blood flow in nudes. Underlying differences in vascular structure, such as smaller tumor blood vessels in C3H versus nude animals, may contribute to strain-dependent variation in vascular function. These data thus identify clear effects of mouse strain on tumor hemodynamics with consequences to PDT and potentially other vascular-mediated therapies.
PMCID: PMC3356280  PMID: 22624014
13.  Evaluation of bacteriochlorophyll-reconstituted low-density lipoprotein nanoparticles for photodynamic therapy efficacy in vivo 
Nanomedicine (London, England)  2011;6(3):475-487.
To evaluate the novel nanoparticle reconstituted bacteriochlorin e6 bisoleate low-density lipoprotein (r-Bchl-BOA-LDL) for its efficacy as a photodynamic therapy agent delivery system in xenografts of human hepatoblastoma G2 (HepG2) tumors.
Materials & methods
Bchl-BOA was encapsulated in the nanoparticle low-density lipoprotein (LDL), a native particle whose receptor’s overexpression is a cancer signature for a number of neoplasms. Evaluation of r-Bchl-BOA-LDL as a potential photosensitizer was performed using a tumor response and foot response assay.
Results & discussion
When compared with controls, tumor regrowth was significantly delayed at injected murine doses of 2 µmole/kg r-Bchl-BOA-LDL after illumination at fluences of 125, 150 or 175 J/cm2. Foot response assays showed that although normal tissue toxicity accompanied the higher fluences it was significantly reduced at the lowest fluence tested.
This research demonstrates that r-Bchl-BOA-LDL is an effective photosensitizer and a promising candidate for further investigation.
PMCID: PMC3137792  PMID: 21542686
bacteriochlorophyll; low-density lipoprotein; nanoparticle; photodynamic therapy; xenograft hepatoma
14.  Increasing Damage to Tumor Blood Vessels during Motexafin Lutetium-PDT through Use of Low Fluence Rate 
Radiation research  2010;174(3):331-340.
Photodynamic therapy (PDT) with low light fluence rate has rarely been studied in protocols that use short drug–light intervals and thus deliver illumination while plasma concentrations of photosensitizer are high, creating a prominent vascular response. In this study, the effects of light fluence rate on PDT response were investigated using motexafin lutetium (10 mg/kg) in combination with 730 nm light and a 180-min drug–light interval. At 180 min, the plasma level of photosensitizer was 5.7 ng/μl compared to 3.1 ng/mg in RIF tumor, and PDT-mediated vascular effects were confirmed by a spasmodic decrease in blood flow during illumination. Light delivery at 25 mW/cm2 significantly improved long-term tumor responses over that at 75 mW/cm2. This effect could not be attributed to oxygen conservation at low fluence rate, because 25 mW/cm2 PDT provided little benefit to tumor hemoglobin oxygen saturation. However, 25 mW/cm2 PDT did prolong the duration of ischemic insult during illumination and was correspondingly associated with greater decreases in perfusion immediately after PDT, followed by smaller increases in total hemoglobin concentration in the hours after PDT. Increases in blood volume suggest blood pooling from suboptimal vascular damage; thus the smaller increases after 25 mW/cm2 PDT provide evidence of more widespread vascular damage, which was accompanied by greater decreases in clonogenic survival. Further study of low fluence rate as a means to improve responses to PDT under conditions designed to predominantly damage vasculature is warranted.
PMCID: PMC2995951  PMID: 20726728
15.  Explicit dosimetry for photodynamic therapy: macroscopic singlet oxygen modeling 
Journal of biophotonics  2010;3(5-6):304-318.
Singlet oxygen (1O2) is the major cytotoxic agent responsible for cell killing for type-II photodynamic therapy (PDT). An empirical four-parameter macroscopic model is proposed to calculate the “apparent reacted 1O2 concentration”, [1O2]rx, as a clinical PDT dosimetry quantity. This model incorporates light diffusion equation and a set of PDT kinetics equations, which can be applied in any clinical treatment geometry. We demonstrate that by introducing a fitting quantity “apparent singlet oxygen threshold concentration” [1O2]rx,sd, it is feasible to determine the model parameters by fitting the computed [1O2]rx to the Photofrin-mediated PDT-induced necrotic distance using interstitially-measured Photofrin concentration and optical properties within each mouse. After determining the model parameters and the [1O2]rx,sd, we expect to use this model as an explicit dosimetry to assess PDT treatment outcome for a specific photosensitizer in an in vivo environment. The results also provide evidence that the [1O2]rx, because it takes into account the oxygen consumption (or light fluence rate) effect, can be a better predictor of PDT outcome than the PDT dose defined as the energy absorbed by the photosensitizer, which is proportional to the product of photosensitizer concentration and light fluence.
PMCID: PMC3071971  PMID: 20222102
photodynamic therapy; explicit dosimetry; singlet oxygen; mathematical modeling

Results 1-15 (15)