α-TEA as a stimulator of tumor autophagy and enhancer of antigen cross-presentation.

Stimulation of apoptosis has been reported as the primary mechanism of tumor cell death induced by alpha-tocopheryloxyacetic acid (α-TEA), an esterase-resistant, semi-synthetic derivative of vitamin E (R-R-R-α-tocopherol). New information now shows that α-TEA also triggers tumor cell autophagy and promotes antigen cross-presentation. Autophagosome-enriched fractions of α-TEA-treated tumor cells (α-TAGS) efficiently cross-primed antigen-specific CD8 (+) T cells and vaccination with dendritic cells (DC) pulsed with α-TAGS reduced lung metastases and increased survival of tumor-bearing mice. Taken together, these observations suggest that both autophagy and apoptosis signaling programs are activated in tumor cells by α-TEA treatment and may contribute to tumor cell death. We propose that autophagy-dependent enhancement of cross-presentation is a novel mechanism of α-TEA-mediated tumor immunity and that α-TEA can be exploited as an adjuvant to enhance the antitumor response.

The vitamin E analogue α-TEA stimulates tumor autophagy and enhances antigen cross-presentation.

The semisynthetic vitamin E derivative alpha-tocopheryloxyacetic acid (α-TEA) induces tumor cell apoptosis and may offer a simple adjuvant supplement for cancer therapy if its mechanisms can be better understood. Here we report that α-TEA also triggers tumor cell autophagy and that it improves cross-presentation of tumor antigens to the immune system. α-TEA stimulated both apoptosis and autophagy in murine mammary and lung cancer cells and inhibition of caspase-dependent apoptosis enhanced α-TEA-induced autophagy. Cell exposure to α-TEA generated double-membrane-bound vesicles indicative of autophagosomes, which efficiently cross-primed antigen-specific CD8(+) T cells. Notably, vaccination with dendritic cells pulsed with α-TEA-generated autophagosomes reduced lung metastases and increased the survival of tumor-bearing mice. Taken together, our findings suggest that both autophagy and apoptosis signaling programs are activated during α-TEA-induced tumor cell killing. We suggest that the ability of α-TEA to stimulate autophagy and enhance cross-priming of CD8(+) T cells might be exploited as an adjuvant strategy to improve stimulation of antitumor immune responses.

Repeat dose study of the novel proapoptotic chemotherapeutic agent alpha-tocopheryloxy acetic acid in mice.

Alpha-tocopheryloxy acetic acid (α-TEA) is an ether derivative of vitamin E and has been shown to suppress tumor growth in various murine and human xenograft tumor models, including melanoma, breast, lung, prostate, and ovarian cancers. The purpose of this study was to assess its safety and pharmacokinetics after repeat dosing in a preclinical murine model. Male and female mice received α-TEA doses of 100, 300, or 1500 mg/kg/day by daily oral gavage for 28 days. α-TEA serum levels were determined weekly by high-performance liquid chromatography with mass spectrometric detection. After 28 days of dosing, complete blood counts were taken, blood chemistry was analyzed, and histology was performed. Pharmacokinetic parameters were determined after single dosing. There was no mortality, and we found no clinical signs of toxicity in any of the α-TEA doses tested. Histopathological evaluation of major organs (heart, lung, kidney, liver, spleen, jejunum, ileum, and cecum) revealed no significant α-TEA treatment-related lesions. Blood counts revealed low-grade anemia but no other significant differences between treatment and control groups. Blood chemistry revealed moderate liver toxicity that was dose dependent and was absent in the lowest dose group. There were no significant sex-specific differences in the toxicity profile. The half-life of orally administered α-TEA was determined to be 52 h. This is the first report comprehensively evaluating the toxicity profile of this novel anticancer drug and will facilitate the design of clinical trials to evaluate the safety and antitumor efficacy of α-TEA in patients with cancer.

Visualization and quantification of intestinal transit and motor function by real-time tracking of 19F labeled capsules in humans.

A combined (19)F and (1)H MRI framework for the assessment of human intestinal transit and motor function is presented. This framework consists of silicone coated polychlorotrifluoroethylene capsules filled with perfluoro-[15]-crown-5-ether as (19)F marker, a flexible (19)F surface coil and a (19)F projection imaging sequence, allowing for real-time tracking of a single or multiple capsules. The capsules (length 11.5 mm, Ø 7.2 mm) contain 140 µL perfluoro-[15]-crown-5-ether and were tested for cytotoxicity and leakage prior to oral administration. A balanced SSFP projection sequence was implemented, yielding a temporal resolution of 133 ms. Optional multi-frequency excitation, allowing for interleaved tracking of differently labeled (19)F capsules, was incorporated. The passage of the (19)F capsules through intestinal sections was monitored in two healthy volunteers. Capsule coordinates were successfully coregistered with anatomical reference scans. Intestinal motility, residence times, lengths and forward velocities were determined. Simultaneous tracking of two capsules allowed for the assessment of peristaltic patterns with correction for respiratory motion. By providing the means for real-time multiple capsule tracking and high resolution anatomical imaging, the presented multinuclear imaging framework has the potential to provide important supplemental information for physiological and pharmaceutical research.

Vesiculated alpha-tocopheryl succinate enhances the anti-tumor effect of dendritic cell vaccines.

Alpha tocopheryl succinate (alpha-TOS) is a non-toxic vitamin E analog under study for its anti-cancer properties. In an earlier study, we showed that alpha-TOS, when used in combination with non-matured dendritic cells (nmDC) to treat pre-established tumors, acts as an effective adjuvant. In this study, we have used vesiculated alpha-TOS (Valpha-TOS), a more soluble form of alpha-TOS that is relevant for clinical use, in combination with dendritic cells to treat pre-established murine tumors. We demonstrate that Valpha-TOS kills tumor cells in vitro and inhibits the growth of pre-established murine lung carcinoma (3LLD122) as effectively as alpha-TOS. The combination of Valpha-TOS plus non-matured or TNF-alpha-matured DC is more effective at inhibiting the growth of established tumors than Valpha-TOS alone. We also observed that Valpha-TOS induces expression of heat shock proteins in tumor cells and that co-incubation of non-matured DC with lysate derived from Valpha-TOS-treated tumor cells leads to DC maturation evidenced by up-regulation of co-stimulatory molecules and secretion of IL-12p70. This study therefore demonstrates the immunomodulatory properties of Valpha-TOS that may account for its adjuvant effect when combined with DC vaccines to treat established tumors.