Multifunctional Liposomes for Image-Guided Intratumoral Chemo-Phototherapy.

Intratumoral (IT) drug injections reduce systemic toxicity, but delivered volumes and distribution can be inconsistent. To improve IT delivery paradigms, porphyrin-phospholipid (PoP) liposomes are passively loaded with three hydrophilic cargos: sulforhodamine B, a fluorophore; gadolinium-gadopentetic acid, a magnetic resonance (MR) agent; and oxaliplatin, a colorectal cancer chemotherapeutic. Liposome composition is optimized so that cargo is retained in serum and storage, but is released in less than 1 min with exposure to near infrared light. Light-triggered release occurs with PoP-induced photooxidation of unsaturated lipids and all cargos release concurrently. In subcutaneous murine colorectal tumors, drainage of released cargo is delayed when laser treatment occurs 24 h after IT injection, at doses orders of magnitude lower than systemic ones. Delayed light-triggering results in substantial tumor shrinkage relative to controls a week following treatment, although regrowth occurs subsequently. MR imaging reveals that over this time frame, pools of liposomes within the tumor migrate to adjacent regions, possibly leading to altered spatial distribution during triggered drug release. Although further characterization of cargo loading and release is required, this proof-of-principle study suggests that multimodal theranostic IT delivery approaches hold potential to both guide injections and interpret outcomes, in particular when combined with chemo-phototherapy.

Mild elevation of body temperature reduces tumor interstitial fluid pressure and hypoxia and enhances efficacy of radiotherapy in murine tumor models.

Human and rodent solid tumors often exhibit elevated interstitial fluid pressure (IFP). This condition is recognized as a prognostic indicator for reduced responses to therapy and decreased disease-free survival rate. In the present study, we tested whether induction of a thermoregulatory-mediated increase in tissue blood flow, induced by exposure of mice to mild environmental heat stress, could influence IFP and other vascular parameters within tumors. Using several murine tumor models, we found that heating results in a sustained reduction in tumor IFP correlating with increased tumor vascular perfusion (measured by fluorescent imaging of perfused vessels, laser Doppler flowmetry, and MRI) as well as a sustained reduction in tumor hypoxia. Furthermore, when radiation therapy was administered 24 hours postheating, we observed a significant improvement in efficacy that may be a result of the sustained reduction in tumor hypoxia. These data suggest, for the first time, that environmental manipulation of normal vasomotor function is capable of achieving therapeutically beneficial changes in IFP and microvascular function in the tumor microenvironment.

Hexylether derivative of pyropheophorbide-a (HPPH) on conjugating with 3gadolinium(III) aminobenzyldiethylenetriaminepentaacetic acid shows potential for in vivo tumor imaging (MR, Fluorescence) and photodynamic therapy.

Conjugates of 3-(1'-hexyloxyethyl)-3-devinyl pyropheophorbide-a (HPPH) with multiple Gd(III)aminobenzyl diethylenetriamine pentacetic acid (ADTPA) moieties were evaluated for tumor imaging and photodynamic therapy (PDT). In vivo studies performed in both mice and rat tumor models resulted in a significant MR signal enhancement of tumors relative to surrounding tissues at 24 h postinjection. The water-soluble (pH: 7.4) HPPH-3Gd(III) ADTPA conjugate demonstrated high potential for tumor imaging by MR and fluorescence. This agent also produced long-term tumor cures via PDT. An in vivo biodistribution study with the corresponding (14)C-analogue also showed significant tumor uptake 24 h postinjection. Toxicological evaluations of HPHH-3Gd(III)ADTPA administered at and above imaging/therapeutic doses did not show any evidence of organ toxicity. Our present study illustrates a novel approach for the development of water-soluble "multifunctional agents", demonstrating efficacy for tumor imaging (MR and fluorescence) and phototherapy.