William McLaughlin

211At radiocolloid therapy: Further observations and comparison with radiocolloids of 32P, 165Dy, and 90Y

We compared the therapeutic efficacy of alpha and beta emitting radiocolloids for the treatment of experimental malignant ascites. 211At is an almost pure alpha-emitter. As 211At-tellurium colloid, the dose survival curve is linear and extrapolates through the origin in a manner similar to other high linear energy transfer radiations. Doses of 25 microCi were curative. Less than curative doses showed a graded prolongation of median survival. In cured mice, long term histological changes were seen in thyroid tissue. Acute changes were seen in the gastrointestinal tract as early as 2 hr after radiocolloid administration; these changes reached a plateau at 6 hr and were essentially gone 36 hr later. By comparison, radiocolloids of the beta emitters 32P, 165Dy and 90Y were not curative, but relatively large doses did substantially prolong median survival. The doses for maximal effect were 150 microCi 32P-chromic phosphate, 8000 microCi ++165Dy-ferric hydroxide macroaggregates and 200 microCi 90Y-citrate. The most compelling reason for the increased therapeutic efficacy of 211At-tellurium colloid is the direct and densely ionizing character of the emitted alpha radiations.

The oil-microcentrifuge assay: A rapid and sensitive method for analyzing specific [3H]estradiol binding in cultured cells

We have developed an oil- microcentrifuge assay system for analyzing the binding of [3H]estradiol in metabolically active MCF-7 and MDA human breast cancer cells. Complete separation of 2 X 10(6) cells from radioactive media can be achieved within 5 s of centrifugation at 12,000 rpm. The [3H]estradiol binding sites in MCF-7 cells are filled within 20 min of radioligand exposure. Using this assay, our MCF-7 cells contain approximately 15,000 high affinity and saturable binding sites. Binding is inhibited by estradiol and tamoxifen but not progesterone. There is no specific binding of [3H]estradiol in MDA cells. This assay is a rapid, sensitive and reproducible method for investigating hormone-receptor binding and ligand specificity in cultured cells; results compare favorably with those obtained by more complex and lengthy techniques.

Experimental Therapeutics Using Alpha Particles

Because of their limited path length and the high LET nature of the emitted radiations, alpha emitters are particularly wellsuited for selective cell destruction if appropriate carrier molecules can be identified. Among the potential carriers for alpha emitters are steroid hormones and melanin precursors. The development of rapid stereo-specific labeling and separation procedures for astatine labeled radiopharmaceuticals will play a critical role in implementing these strategies.

Abstract 2864: Molecular imaging of early inflammatory response during hyperplasia and/or colitis in response to bacterial infection.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Inflammatory diseases such as ulcerative colitis recruit myeloid cells and result in inflammatory responses such as generation of reactive oxygen species (ROS). Development of non-invasive luminescence imaging approaches is needed to evaluate these inflammatory responses. We developed methodologies to show that vibration induced gut inflammation can be determined using luminescence imaging approach in a non-invasive fashion (Papineni and Vizard, World Molecular Imaging Congress 2012). Citrobacter rodentium (CR) is a natural bacterial pathogen that infects the distal colon of mice and induces transmissible murine colonic hyperplasia (TMCH). Here we determined the early inflammatory response (ROS activity) to intestinal infection by CR in a longitudinal study. We further assessed the effects of allelic variation on murine chromosome 11 (B6.CAST. 11) on the inflammatory response. The ROS activity was monitored in real-time in vivo using L-012 (8-amino-5-chloro-7-phenylpyridol [3,4-d]pyridazine-1,4(2H,3H) dione), a chemiluminescence reporter, using planar multimodal imaging system. 0.1 ml of 1 mg/ml L-012 probe was injected (i.p.) in control and the experimental mice that were subjected to CR infection. Necrosis was imaged (post-infection day-19) using a fluorescent probe containing a bis (zinc2+dipicolylamine, Zn- DPA) motif which binds with high affinity to apoptotic, necrotic, and bacterial surfaces. Significant difference in the basal gut ROS activity was found in mice with allelic variation on chromosome 11 compared to the wild type littermates. Robust elevation in ROS activity was observed in both the wild type and B6.CAST.11mice that were infected with CR (post infection 9, 12, 19 days). The variation in the levels of ROS activity however was very distinct between the wild type and B6.CAST.11 mice indicating the contribution of molecular determinants at the chromosome 11. The potential advantages in these real-time ROS monitoring methodologies by in vivo imaging, in understanding mechanisms of infection, inflammation, and development of better intervention strategies will be elaborated. Citation Format: Rao Papineni, Ishfaq Ahmed, Steven LeVine, Kenneth Bradley, William Mclaughlin, John Pizzonia, Shahid Umar. Molecular imaging of early inflammatory response during hyperplasia and/or colitis in response to bacterial infection. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2864. doi:10.1158/1538-7445.AM2013-2864