Radio-resistance

Now the main point is to define what we call radio resistance. According to Eq. 2 we could conventionally adopt as a measure of it the amount of radiation needed to be absorbed to produce a fixed value for I/I0 or correspondingly for vrC or vrkD. To achieve accuracy in the measurements and to assure the validity of the law involved, the value of 0.6 for ///a has been chosen, which cor-... 

Hypoxic cells are three times more radio-resistant than well-oxygenated cells (OER = 3) for low-LET radiation. The presence of a small percentage of hypoxic cells (1% or even 0.1%) can thus make the tumor radio-resistant. 

Fig. 8 illustrates how increasing LET reduces the differences in radiosensitivity related to the position of the cells in the mitotic cycle [31]. Cells in stationary phase and in S phase are significantly more radio-resistant than mitotic cells. 

In the solid state, the drugs are radio-resistant until the Standard Absorbed Dose (SAD) (25 kGy) but some changes in the organoleptic properties may be reported at this dose by decreasing the doses, some discoloration and/or smell may be reduced. 

Radio-resistant Ionizing radiation Fresh water and soil (13)... 

Yasuda, H. (2008). Solid tumor physiology and hypoxia-induced chemo/radio-resistance Novel strategy for cancer therapy Nitric oxide donor as a therapeutic enhancer. Nitric Oxide 19, 205-216. 

Modulation of Chemo-resistance and Radio-resistance by NO-Mimetic Agents... 

Among a plethora of other functions, NF-kB acts in an antiapoptotic manner and, therefore, confers drug- and radio-resistance (Ahmed and Li 2008 Nakanishi and Toi 2005). NF-kB is a complex consisting of p50, p65, and I-KBa (Aggarwal 2003). Phosphorylation and degradation of the inhibitory subunit, I- KBa, activate the complex, which then translocates from the cytosol into the nucleus (Kumar et al. 2004). As transcription factor, NF-kB induces the expression of many genes, including antiapoptotic ones, such as survivin, TRAF, cFLIP, Bcl-2, and Bcl-xL. Since NO donors inhibit p50 phosphorylation by 5-nitrosylation (Marshall and Stamler 2001), NO overcomes NF-KB-mediated therapy resistance. 

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