We have investigated the molecular features of recombinant membranes that are necessary for the photochemical function of rhodopsin. The magnitude of the metarhodopsin I to metarhodopsin II phototransient following a 25% +/- 3% bleaching flash was used as a criterion of photochemical activity at 28 degrees C and pH 7.0. Nativelike activity of rhodopsin can be reconstituted with an extract of total lipids from rod outer segment membranes, demonstrating that the protein is minimally perturbed by the reconstitution protocol. Rhodopsin photochemical activity is enhanced by phosphatidylethanolamine head groups and docosahexaenoyl (22:6 omega 3) acyl chains. An equimolar mixture of phosphatidylethanolamine and phosphatidylcholine containing 50 mol% docosahexaenoyl chains results in optimal photochemical function. These results suggest the importance of both the head-group and acyl chain composition of the rod outer segment lipids in the visual process. The extracted rod lipids and those lipid mixtures favoring the conformational change from metarhodopsin I to II can undergo lamellar (L alpha) to inverted hexagonal (HII) phase transitions near physiological temperature. Interaction of rhodopsin with membrane lipids close to a L alpha to HII (or cubic) phase boundary may thus lead to properties which influence the energetics of conformational states of the protein linked to visual function.

Lung cancer (specifically, non-small cell lung cancer; NSCLC) is the leading cause of cancer-related deaths in the United States. Poor response rates and survival with current treatments clearly indicate the urgent need for developing an effective means to treat NSCLC. Magnetic hyperthermia is a non-invasive approach for tumor ablation, and is based on heat generation by magnetic materials, such as superparamagnetic iron oxide (SPIO) nanoparticles, when subjected to an alternating magnetic field. However, inadequate delivery of magnetic nanoparticles to tumor cells can result in sub-lethal temperature change and induce resistance while non-targeted delivery of these particles to the healthy tissues can result in toxicity. In our studies, we evaluated the effectiveness of tumor-targeted SPIO nanoparticles for magnetic hyperthermia of lung cancer. EGFR-targeted, inhalable SPIO nanoparticles were synthesized and characterized for targeting lung tumor cells as well as for magnetic hyperthermia-mediated antitumor efficacy in a mouse orthotopic model of NSCLC. Our results show that EGFR targeting enhances tumor retention of SPIO nanoparticles. Further, magnetic hyperthermia treatment using targeted SPIO nanoparticles resulted in significant inhibition of in vivo lung tumor growth. Overall, this work demonstrates the potential for developing an effective anticancer treatment modality for the treatment of NSCLC based on targeted magnetic hyperthermia.

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This investigation is part of an effort to develop chemoprevention for carcinogenesis of the lung. It focuses on the efficacy of low doses of synthetic glucocorticoids administered either as single agents or in combination with a second compound, myo-inositol. Glucocorticoids are potent inhibitors of carcinogenesis. The use of low doses is important to avoid potential side-effects. The synthetic glucocorticoid budesonide, administered by aerosol for 20 s three times a week, was studied to determine its effects on benzo[a]pyrene-induced pulmonary adenoma formation in female A/J mice. Two dose levels were employed, 10 and 25 microg/kg body wt. The lower dose produced a 34% reduction in lung tumor formation and the higher dose level a 60% reduction in lung tumors. In additional groups of mice, the effects of 0.3% myo-inositol added to the diet was found to reduce pulmonary tumor formation by 53%. The two agents given in combination resulted in a greater inhibition of lung tumor formation than either by itself. Budesonide at 10 microg/kg body wt plus 0.3% myo-inositol reduced the number of tumors by 60% and budesonide at 25 microg/kg body wt plus 0.3% myo-inositol reduced lung tumor formation by 79%. To determine whether a glucocorticoid other than budesonide would have inhibitory effects in this experimental model, beclomethasone dipropionate administered by aerosol for 20 s three times a week was studied as a single agent and showed almost identical inhibitory properties to budesonide. The doses of the glucocorticoids calculated on a daily basis are within the range of those used widely for control of chronic allergic respiratory diseases in the human. The capacity of low doses of inhaled glucocorticoids to prevent pulmonary neoplasia and the enhancement of this preventive effect by myo-inositol, an essentially non-toxic compound, are findings that should encourage further work to evaluate the applicability of these agents to the prevention of neoplasia of the lung in the human.

Cancer stem cells (CSCs) are a subpopulation of cancer cells that have stem cell-like properties and are thought to be responsible for tumor drug resistance and relapse. Therapies that can effectively eliminate CSCs will, therefore, likely inhibit tumor recurrence. The objective of our study was to determine the susceptibility of CSCs to magnetic hyperthermia, a treatment that utilizes superparamagnetic iron oxide nanoparticles placed in an alternating magnetic field to generate localized heat and achieve selective tumor cell kill. SPIO NPs having a magnetite core of 12 nm were used to induce magnetic hyperthermia in A549 and MDA-MB-231 tumor cells. Multiple assays for CSCs, including side population phenotype, aldehyde dehydrogenase expression, mammosphere formation, and in vivo xenotransplantation, indicated that magnetic hyperthermia reduced or, in some cases, eliminated the CSC subpopulation in treated cells. Interestingly, conventional hyperthermia, induced by subjecting cells to elevated temperature (46 °C) in a water bath, was not effective in eliminating CSCs. Our studies show that magnetic hyperthermia has pleiotropic effects, inducing acute necrosis in some cells while stimulating reactive oxygen species generation and slower cell kill in others. These results suggest the potential for lower rates of tumor recurrence after magnetic hyperthermia compared to conventional cancer therapies.