Ras activation promotes the survival of tumor cells after DNA damage. To reverse this survival advantage, Ras signaling has been targeted for inhibition. Other contributors to Ras-mediated DNA damage survival have been identified using pharmacologic inhibition of signaling, but this approach is limited by the specificity of the inhibitors used and their toxicity. To better define components of Ras signaling that could be inhibited in a clinical setting, RNA interference was used to selectively block expression of specific isoforms of Ras, phosphoinositide 3 (PI3) kinase, and Akt. Inhibition of oncogenic Ras expression decreased both phospho-Akt and phospho-p42/44 mitogenactivated protein (MAP) kinase levels and reduced clonogenic survival. Because pharmacologic inhibition of PI3 kinases and Akt radiosensitized cell lines with active Ras signaling, whereas inhibition of the MAP/extracellular signal-regulated kinase (ERK) kinase/ERK pathway did not, we examined the contribution of PI3 kinases and Akts to radiation survival. Selective inhibition the PI3 kinase P110A + p85B isoforms reduced Akt phosphorylation and radiation survival. Similarly, inhibition of Akt-1 reduced tumor cell radiation survival. Inhibition of Akt-2 or Akt-3 had less effect. Retroviral transduction and overexpression of mouse Akt-1 was shown to rescue cells from inhibition of endogenous human Akt-1 expression. This study shows that Ras signaling to the PI3 kinase-Akt pathway is an important contributor to survival, whether Ras activation results from mutation of ras or overexpression of epidermal growth factor receptor. This study further shows that selective inhibition of the PI3 kinase P110A + p85B isoforms or Akt-1 could be a viable approach to sensitizing many tumor cells to cytotoxic therapies. (Cancer Res 2005; 65(17): 7902-10)

Preprotachykinin-I gene (PPT-I) encodes several peptides with organ-specific functions that link the neuroendocrine-immune-hemopoietic axis. We cloned upstream of the initiation site of human PPT-I promoter and identified consensus sequences for two cAMP response elements (CRE). PPT-I is induced by cytokines including those that signal through the cAMP pathway. Therefore, we studied the role of the two CRE in IL-1α and stem cell factor (SCF) stimulation of bone marrow stroma because both cytokines induce endogenous PPT-I in these cells and activate the cAMP pathway. Furthermore, bone marrow stroma expresses the transcription factors regulated by the cAMP pathways such as the repressor (ICERIIγ) and activator (CREMτ). Mutagenesis of the two CRE and/or cotransfection with vectors that express ICERIIγ or CREMτ indicated that the two CRE have major roles in PPT-I expression. The two CRE are also required for optimal promoter activity by SCF and IL-1α. A particular cytokine could concomitantly induce PPT-I and the high affinity G protein-coupled receptor for PPT-I peptides, NK-1R. We showed that SCF, a representative cytokine, induced PPT-I and NK-1R leading to autocrine and/or paracrine cell activation. Because NK-1R activates cAMP through the G protein, the results suggest that the presence of CRE sequences within PPT-I promoter could be important in the regulation of PPT-I expression by cytokines, irrespective of their ability to signal through cAMP. As PPT-I is implicated in hemopoietic regulation, immune responses, breast cancer, and other neural functions, these studies add to the basic biology of these processes and could provide targets for drug development.

Objectives: The cancer burden in low- and middle-income countries (LMIC) is substantial. The purpose of this study was to identify and describe country and region-specific patterns of radiotherapy (RT) facilities in LMIC.Methods: A systematic review of the literature was undertaken. A search strategy was developed to include articles on radiation capacity in LMIC from the following databases: PubMed, Embase, CINAHL Plus, Global Health, and the Latin American and Caribbean System on Health Sciences Information. Searches included all literature up to April 2013.Results: A total of 49 articles were included in the review. Studies reviewed were divided into one of four regions: Africa, Asia, Eastern Europe, and South America. The African continent has the least amount of resources for RT. Furthermore, a wide disparity exists, as 60% of all machines on the continent are concentrated in Egypt and South Africa while 29 countries in Africa are still lacking any RT resource. A significant heterogeneity also exists across Southeast Asia despite a threefold increase in megavoltage teletherapy machines from 1976 to 1999, which corresponds with a rise in economic status. In LMIC of the Americas, only Uruguay met the International Atomic Energy Agency recommendations of 4 MV/million population, whereas Bolivia and Venezuela had the most radiation oncologists (>1 per 1000 new cancer cases). The main concern with the review of RT resources in Eastern Europe was the lack of data.Conclusion: There is a dearth of publications on RT therapy infrastructure in LMIC. However, based on limited published data, availability of RT resources reflects the countries’ economic status. The challenges to delivering radiation in the discussed regions are multidimensional and include lack of physical resources, lack of human personnel, and lack of data. Furthermore, access to existing RT and affordability of care remains a large problem.

Radiation does not seem to increase the risk of cardiac mortality or secondary malignancy in patients with malignant thymoma. Although the routine use of postoperative radiotherapy in malignant thymoma does not appear warranted, high-risk patients may benefit from adjuvant radiation. This study can help to design prospective trials to further establish the role of radiotherapy in malignant thymoma.

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