Browsing by Subject "Ionizing radiation"

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    NQO1-dependent, tumor-selective radiosensitization of non-small cell lung cancers
    (American Association for Cancer Research, 2019-04-15) Motea, Edward A.; Huang, Xiumei; Singh, Naveen; Kilgore, Jessica; Williams, Noelle; Xie, Xian-Jin; Gerber, David E.; Beg, Muhammad Shaalan; Bey, Erik A.; Boothman, David A.; Biochemistry and Molecular Biology, School of Medicine
    Purpose: Development of tumor-specific therapies for the treatment of recalcitrant non-small cell lung cancers (NSCLCs) are urgently needed. Here, we investigated the ability of ß-lapachone (ß-lap, ARQ761 in clinical form) to selectively potentiate the effects of ionizing radiation (IR, 1–3 Gy) in NSCLCs that over-express NAD(P)H:Quinone Oxidoreductase 1 (NQO1). Experimental Design: The mechanism of lethality of low dose IR in combination with sublethal doses of ß-lap were evaluated in NSCLC lines in vitro and validated in subcutaneous and orthotopic xenograph models in vivo. Pharmacokinetics and pharmacodynamics (PK/PD) studies comparing single versus co-treatments were performed to validate therapeutic efficacy and mechanism of action. Results: ß-Lap administration after IR treatment hyperactivated PARP, greatly lowered NAD+/ATP levels, and increased DSB lesions over time in vitro. Radiosensitization of orthotopic, as well as subcutaneous, NSCLCs occurred with high apparent cures (>70%), even though 1/8 ß-lap doses reach subcutaneous versus orthotopic tumors. No methemoglobinemia or long-term toxicities were noted in any normal tissues, including mouse liver that expresses the highest level of NQO1 (~12 Units) of any normal tissue. PK/PD responses confirm that IR + ß-lap treatments hyperactivate PARP activity, greatly lower NAD+/ATP levels and dramatically inhibit DSB repair in exposed NQO1+ cancer tissue, while low NQO1 levels and high levels of Catalase in associated normal tissue were protective. Conclusion: Our data suggest that combination of sublethal doses of ß-lap and IR is a viable approach to selectively treat NQO1-overexpressing NSCLC and warrant a clinical trial using low-dose IR + ß-lapachone against patients with NQO1+ NSCLCs.
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    Understanding, justifying, and optimizing radiation exposure for CT imaging in nephrourology
    (Springer Nature, 2019-04) Ferrero, Andrea; Takahashi, Naoki; Vrtiska, Terri J.; Krambeck, Amy E.; Lieske, John C.; McCollough, Cynthia H.; Urology, School of Medicine
    An estimated 4-5 million CT scans are performed in the USA every year to investigate nephrourological diseases such as urinary stones and renal masses. Despite the clinical benefits of CT imaging, concerns remain regarding the potential risks associated with exposure to ionizing radiation. To assess the potential risk of harmful biological effects from exposure to ionizing radiation, understanding the mechanisms by which radiation damage and repair occur is essential. Although radiation level and cancer risk follow a linear association at high doses, no strong relationship is apparent below 100 mSv, the doses used in diagnostic imaging. Furthermore, the small theoretical increase in risk of cancer incidence must be considered in the context of the clinical benefit derived from a medically indicated CT and the likelihood of cancer occurrence in the general population. Elimination of unnecessary imaging is the most important method to reduce imaging-related radiation; however, technical aspects of medically justified imaging should also be optimized, such that the required diagnostic information is retained while minimizing the dose of radiation. Despite intensive study, evidence to prove an increased cancer risk associated with radiation doses below ~100 mSv is lacking; however, concerns about ionizing radiation in medical imaging remain and can affect patient care. Overall, the principles of justification and optimization must remain the basis of clinical decision-making regarding the use of ionizing radiation in medicine.