Normal Tissue Protection Research Articles

Implications récentes des équipes françaises en oncologie radiothérapie et radiobiologie clinique

Many clinical studies have showed the key role of radiotherapy in anticancer treatment strategy. Radiations are delivered alone or in combination with systemic therapies. In recent years, the main goal of all clinical developments has focused on improving clinical benefit, with an increased tumour control and a higher normal tissue protection. This research was designed to reduce local recurrences, to increase recurrence-free or overall survival and to decrease acute and late effects. Technological and biological evolutions (or revolutions) accompanied clinicians to improve clinical benefit, namely with strong progress in radiology and better understanding of radiobiology, particularly at the molecular level. Differences in tumour and normal tissues radiosensitivity are nowadays integrated in daily clinical practice of radiation oncologists. The current report details the last 5-year developments of clinical and translational research in radiation oncology, especially the role of French teams in the development of personalized treatment.

Locoregional extension patterns of nasopharyngeal carcinoma and suggestions for clinical target volume delineation

Clinical target volume (CTV) delineation is crucial for tumor control and normal tissue protection. This study aimed to define the locoregional extension patterns of nasopharyngeal carcinoma (NPC) and to improve CTV delineation. Magnetic resonance imaging scans of 2366 newly diagnosed NPC patients were reviewed. According to incidence rates of tumor invasion, the anatomic sites surrounding the nasopharynx were classified into high-risk (>30%), medium-risk (5%–30%), and low-risk (<5%) groups. The lymph node (LN) level was determined according to the Radiation Therapy Oncology Group guidelines, which were further categorized into the upper neck (retropharyngeal region and level II), middle neck (levels III and Va), and lower neck (levels IV and Vb and the supraclavicular fossa). The high-risk anatomic sites were adjacent to the nasopharynx, whereas those at medium- or low-risk were separated from the nasopharynx. If the high-risk anatomic sites were involved, the rates of tumor invasion into the adjacent medium-risk sites increased; if not, the rates were significantly lower (P < 0.01). Among the 1920 (81.1%) patients with positive LN, the incidence rates of LN metastasis in the upper, middle, and lower neck were 99.6%, 30.2%, and 7.2%, respectively, and skip metastasis happened in only 1.2% of patients. In the 929 patients who had unilateral upper neck involvement, the rates of contralateral middle neck and lower neck involvement were 1.8% and 0.4%, respectively. Thus, local disease spreads stepwise from proximal sites to distal sites, and LN metastasis spreads from the upper neck to the lower neck. Individualized CTV delineation for NPC may be feasible.

Histone Deacetylase Inhibitors Influence Chemotherapy Transport by Modulating Expression and Trafficking of a Common Polymorphic Variant of the ABCG2 Efflux Transporter

Histone deacetylase inhibitors (HDI) have exhibited some efficacy in clinical trials, but it is clear that their most effective applications have yet to be fully determined. In this study, we show that HDIs influence the expression of a common polymorphic variant of the chemotherapy drug efflux transporter ABCG2, which contributes to normal tissue protection. As one of the most frequent variants in human ABCG2, the polymorphism Q141K impairs expression, localization, and function, thereby reducing drug clearance and increasing chemotherapy toxicity. Mechanistic investigations revealed that the ABCG2 Q141K variant was fully processed but retained in the aggresome, a perinuclear structure, where misfolded proteins aggregate. In screening for compounds that could correct its expression, localization, and function, we found that the microtubule-disrupting agent colchicine could induce relocalization of the variant from the aggresome to the cell surface. More strikingly, we found that HDIs could produce a similar effect but also restore protein expression to wild-type levels, yielding a restoration of ABCG2-mediated specific drug efflux activity. Notably, HDIs did not modify aggresome structures but instead rescued newly synthesized protein and prevented aggresome targeting, suggesting that HDIs disturbed trafficking along microtubules by eliciting changes in motor protein expression. Together, these results showed how HDIs are able to restore wild-type functions of the common Q141K polymorphic isoform of ABCG2. More broadly, our findings expand the potential uses of HDIs in the clinic.

Radio-sensitivities and angiogenic signaling pathways of irradiated normal endothelial cells derived from diverse human organs

The purpose of the present investigation was to study the effects of ionizing radiation on endothelial cells derived from diverse normal tissues. We first compared the effects of radiation on clonogenic survival and tube formation of endothelial cells, and then investigated the molecular signaling pathways involved in endothelial cell survival and angiogenesis. Among the different endothelial cells studied, human hepatic sinusoidal endothelial cells (HHSECs) were the most radio-resistant and human dermal microvascular endothelial cells were the most radio-sensitive. The radio-resistance of HHSECs was related to adenosine monophosphate-activated protein kinase and p38 mitogen-activated protein kinase-mediated expression of MMP-2 and VEGFR-2, whereas the increased radio-sensitivity of HDMECs was related to extracellular signal-regulated kinase-mediated generation of angiostatin. These observations demonstrate that there are distinct differences in the radiation responses of normal endothelial cells obtained from diverse organs, which may provide important clues for protection of normal tissue from radiation exposure.

Normal tissue protection for improving radiotherapy: Where are the Gaps?

Any tumor could be controlled by radiation therapy if sufficient dose were delivered to all tumor cells. Although technological advances in physical treatment delivery have been developed to allow more radiation dose conformity, normal tissues are invariably included in any radiation field within the tumor volume and also as part of the exit and entrance doses relevant for particle therapy. Mechanisms of normal tissue injury and related biomarkers are now being investigated, facilitating the discovery and development of a next generation of radiation protectors and mitigators. Bringing recent research advances stimulated by development of radiation countermeasures for mass casualties, to clinical cancer care requires understanding the impact of protectors and mitigators on tumor response. These may include treatments that modify cellular damage and death processes, inflammation, alteration of normal flora, wound healing, tissue regeneration and others, specifically to counter cancer site-specific adverse effects to improve outcome of radiation therapy. Such advances in knowledge of tissue and organ biology, mechanisms of injury, development of predictive biomarkers and mechanisms of radioprotection have re-energized the field of normal tissue protection and mitigation. Since various factors, including organ sensitivity to radiation, cellular turnover rate, and differences in mechanisms of injury manifestation and damage response vary among tissues, successful development of radioprotectors/mitigators/treatments may require multiple approaches to address cancer site specific needs. In this review, we discuss examples of important adverse effects of radiotherapy (acute and intermediate to late occurring, when it is delivered either alone or in conjunction with chemotherapy, and important limitations in the current approaches of using radioprotectors and/or mitigators for improving radiation therapy. Also, we are providing general concepts for drug development for improving radiation therapy.

Influence of robust optimization in intensity‐modulated proton therapy with different dose delivery techniques

The distal edge tracking (DET) technique in intensity-modulated proton therapy (IMPT) allows for high energy efficiency, fast and simple delivery, and simple inverse treatment planning; however, it is highly sensitive to uncertainties. In this study, the authors explored the application of DET in IMPT (IMPT-DET) and conducted robust optimization of IMPT-DET to see if the planning technique's sensitivity to uncertainties was reduced. They also compared conventional and robust optimization of IMPT-DET with three-dimensional IMPT (IMPT-3D) to gain understanding about how plan robustness is achieved. They compared the robustness of IMPT-DET and IMPT-3D plans to uncertainties by analyzing plans created for a typical prostate cancer case and a base of skull (BOS) cancer case (using data for patients who had undergone proton therapy at our institution). Spots with the highest and second highest energy layers were chosen so that the Bragg peak would be at the distal edge of the targets in IMPT-DET using 36 equally spaced angle beams; in IMPT-3D, 3 beams with angles chosen by a beam angle optimization algorithm were planned. Dose contributions for a number of range and setup uncertainties were calculated, and a worst-case robust optimization was performed. A robust quantification technique was used to evaluate the plans' sensitivity to uncertainties. With no uncertainties considered, the DET is less robust to uncertainties than is the 3D method but offers better normal tissue protection. With robust optimization to account for range and setup uncertainties, robust optimization can improve the robustness of IMPT plans to uncertainties; however, our findings show the extent of improvement varies. IMPT's sensitivity to uncertainties can be improved by using robust optimization. They found two possible mechanisms that made improvements possible: (1) a localized single-field uniform dose distribution (LSFUD) mechanism, in which the optimization algorithm attempts to produce a single-field uniform dose distribution while minimizing the patching field as much as possible; and (2) perturbed dose distribution, which follows the change in anatomical geometry. Multiple-instance optimization has more knowledge of the influence matrices; this greater knowledge improves IMPT plans' ability to retain robustness despite the presence of uncertainties.

Curtailing side effects in chemotherapy: a tale of PKCδ in cisplatin treatment

The efficacy of chemotherapy is often limited by side effects in normal tissues. This is exemplified by cisplatin, a widely used anti-cancer drug that may induce serious toxicity in normal tissues and organs including the kidneys. Decades of research have delineated multiple signaling pathways that lead to kidney cell injury and death during cisplatin treatment. However, the same signaling pathways may also be activated in cancer cells and be responsible for the chemotherapeutic effects of cisplatin in tumors and, as a result, blockade of these pathways is expected to reduce the side effects as well as the anti-cancer efficacy. Thus, to effectively curtail the side effects, it is imperative to elucidate and target the cell killing mechanisms that are specific to normal (and not cancer) tissues. Our recent work identified protein kinase C δ (PKCδ) as a new and critical mediator of cisplatin-induced kidney cell injury and death. Importantly, inhibition of PKCδ enhanced the chemotherapeutic effects of cisplatin in several tumor models while alleviating the side effect in kidneys, opening a new avenue for normal tissue protection during chemotherapy.

P2-02-10: Differential Targeting of the RB-Pathway To Expand the Therapeutic Index in the Treatment of Triple Negative Breast Cancer.

Abstract Background: The retinoblastoma tumor suppressor (RB) is inactivated in a significant fraction of triple negative breast cancers (TNBC). RB loss is believed to contribute to tumor initiation and progression, and provocative data suggest that RB loss is associated with improved response to cytotoxic chemotherapy. Unfortunately, such therapies have significant side effects that impinge on patient quality of life. Here we explored the ability to specifically target RB loss in TNBC to expand the therapeutic index by protecting against undesired side-effects of chemotherapy. Experimental Design: A combination of cell culture and xenograft models of triple negative breast cancer were used to evaluate how RB-status impinges on sensitivity to chemotherapy. These models were complemented by the analyses of clinical specimens from patients treated with chemotherapy. Parallel use of agents that activate RB function with high specificity were interrogated as potential tissue protectors to ameliorate side effect of chemotherapy. Results: RB loss in preclinical models is associated with increased sensitivity to conventional cytotoxic chemotherapies that are frequently employed in the treatment of TNBC. The findings were recapitulated through the analyses of clinical specimens, and suggest that the loss of RB could be particularly useful in defining TNBC patients with improved response to chemotherapy. Combination studies of pharmacological activation of the RB pathway and cytotoxic chemotherapies commonly used to treat TNBC demonstrated that activation of RB can modulate the efficacy of cytotoxic compounds in the treatment of TNBC. Importantly, functional studies indicated that RB pathway activation limits cardiotoxicity associated with anthracycline based treatments and correspondingly improve cardiac function in animal studies. Conclusions: Combined, these studies indicate that RB pathway status could be utilized in the clinic to direct combination treatments that would exploit the sensitivity of RB-deficient tumors to cytotoxic chemotherapies while simultaneously providing protection for normal tissues. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-02-10.

Soy isoflavones radiosensitize lung cancer while mitigating normal tissue injury

BackgroundWe have demonstrated that soy isoflavones radiosensitize cancer cells. Prostate cancer patients receiving radiotherapy (RT) and soy tablets had reduced radiation toxicity to surrounding organs. We have now investigated the combination of soy with RT in lung cancer (NSCLC), for which RT is limited by radiation-induced pneumonitis. MethodsHuman A549 NSCLC cells were injected i.v. in nude mice to generate lung tumor nodules. Lung tumor-bearing mice were treated with left lung RT at 12Gy and with oral soy treatments at 1mg/day for 30days. Lung tissues were processed for histology. ResultsCompared to lung tumor nodules treated with soy isoflavones or radiation, lung tissues from mice treated with both modalities showed that soy isoflavones augmented radiation-induced destruction of A549 lung tumor nodules leading to small residual tumor nodules containing degenerating tumor cells with large vacuoles. Soy isoflavones decreased the hemorrhages, inflammation and fibrosis caused by radiation in lung tissue, suggesting protection of normal lung tissue. ConclusionsSoy isoflavones augment destruction of A549 lung tumor nodules by radiation, and also mitigate vascular damage, inflammation and fibrosis caused by radiation injury to normal lung tissue. Soy could be used as a non-toxic complementary approach to improve RT in NSCLC.

SU‐E‐T‐857: Comparison of Nasopharyngeal Carcinoma IMRT Plans from Four Commercial Treatment Planning Systems (TPS)

Purpose: Different treatment planning systems (TPS) use different treatment optimization and leaf sequencing algorithms. This work compares nasopharyngeal carcinoma (NPC) IMRT plans optimized with four commercial TPSs to investigate the plan quality in terms of target conformity and delivery efficiency. Methods: Five nasopharyngeal carcinoma cases were planned with the Corvus, Monaco, Pinnacle and Xio TPSs by experienced planners using appropriate optimization parameters and dose constraints to meet the clinical acceptance criteria. Plans were normalized for at least 95% of PTV to receive the prescription dose (Dp). Dose‐volume histograms and isodose distributions were compared. Other quantities such as Dmin (the minimum dose received by 99% of CTV/PTV), Dmax (the maximum dose received by 1% of CTV/PTV), D100, D95, D90, V110%, V105%, V100% (the volume of GTV/CTV/PTV receiving 110%, 105%, 100% of Dp), conformity index(CI), homogeneity index (HI), the Dmax of spinal cord, brain stem, nerves and lens&amp;#65292;the volume of receiving 30Gy (V30) and the mean dose to parotids (Dmean) were evaluated. Total segments and MUs were also compared. Results: While all plans meet target dose specifications and normal tissue constraints, the maximum GTVCI of Pinnacle plans was up to 0.43 and the minimum of Corvus plans was only 0.17, these four TPSs PTVCI had comparable and no difference. The GTVHI, CTVHI and PTVHI of Pinnacle plans are all very low and show a very good dose distribution. Corvus plans provided the lower, better protection of normal tissue. The Monaco and Pinnacle plans require significantly less segments and MUs to deliver than the Corvus plans. Conclusions: To deliver on a Varian linear‐accelerator, the Pinnacle plans show a very good dose distribution. Corvus plans provided the lower, better protection of normal tissue. The Monaco and Pinnacle plans have faster beam delivery.

SU‐E‐T‐845: Benefits from Achillesˈ Heel of Intensity‐Modulated Proton Therapy via Worst‐Case Robust Optimization

Purpose: to minimize the influence of ranger and patient setup uncertainties in intensity‐modulated proton therapy (IMPT), thus achieving the goal of “what you see is what you get” results in IMPT. Methods: A new efficient optimization scheme, which uses memory‐distributed parallelization on a multi‐processor system, is devised. Our method minimizes the possible hot spots in target volumes by penalizing not only underdosing but also overdosing in the target volumes in the objective function. Range and setup uncertainties are considered simultaneously with some simplifications. The optimization is done using the L‐BFGS method and parallelized with beamlet domain decomposition. Our approach is essentially not restrained by the memory available at one computing node and can easily be expanded to address more demanding problems in the future. Results: Compared with conventional treatment plans optimized based on planning target volumes (PTVs), our method yields plans that are considerably less sensitive to range and setup uncertainties and provides better protection for organs at risk. After robust optimization, the dose distribution is static to the CTV regardless of range and/or setup uncertainties, therefore reducing the sensitivity of the CTV coverage. This unique characteristic allows that the dose distribution is not necessarily conformal inside the whole volume of PTV, but rather a much smaller volume enclosing the CTV. Better normal tissue protection is thus accomplished by underdosing the margin of the PTV while not compromising the CTV coverage. Conclusions: Our results demonstrate the importance of robust optimization and challenge the effectiveness of the use of PTV to account for uncertainties in IMPT planning. Actually we can get some benefits rather than impediments from the sensitive dose distribution to uncertainties of IMPT. Thus, ideally all IMPT plans should be robustly optimized and our approach has great potential to make previously unreliable IMPT plans reliable.

Abstract LB-160: Dual application of TLR5 agonist in cancer treatment: A single agent combines supporting care and antitumor activities

Abstract We have previously shown the strong radioprotective properties of TLR5 agonist flagellin in both mouse and non-human primate models (Burdelya et al., 2008, Science 320: 226–230). A pharmacologically optimized flagellin derivative, Protectan CBLB502, is currently at an advanced stage of development as a prospective radiation antidote for biodefense applications. By testing CBLB502 in combination with radiation treatment of experimental mouse tumors in vivo, we demonstrated that its tissue protection properties are limited to normal tissues with no tumor protection detected in any of numerous mouse tumor models. For example, injections of CBLB502 significantly reduced the severity of mucositis and dermatitis associated with local fractioned irradiation of the head and neck area of mice with syngeneic orthotopically grown head and neck carcinoma with no reduction of antitumor effect of experimental radiotherapy. On the contrary, use of CBLB502 led to enhanced tumor suppression by radiation and produced a detectable tumor suppressive effect even without irradiation. Similar results were obtained in s.c. grown syngeneic colon Wart tumors in rats. In this model, administration of CBLB502 reduced the severity of irinotecan-induced diarrhea, but did not interfere with the anti-tumor effect of the drug. Moreover, use of CBLB502 as a single agent had a pronounced antitumor effect in the majority of Wart tumor-carrying rats. Comparison of the effect of CBLB502 on in vivo growth of isogenic pairs of tumor cell lines differing in their TLR5 status showed that the antitumor effect of the TLR5 agonist is TLR5 dependent and is associated with tumor infiltration by immunocytes, presumably attracted following activation of TLR5 signaling in the tumor cells. Remarkably, CBLB502 caused an immunotherapeutic effect in TLR5-negative tumors growing as experimental metastases in the liver which was found to be the primary target of TLR5 agonist. The liver responds to CBLB502 injection by massive and rapid activation of NF-kB in all hepatocytes. This results in dramatic changes in the content of secreted factors, attraction of immunocytes and a strong reversible increase in liver resistance to a variety of toxic agents. Based on these results, we project clinical applications of CBLB502 as a bi-functional therapeutic agent with supporting care (protection of normal tissues from radio- and chemotherapy side effects) and immunotherapeutic activities. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-160. doi:10.1158/1538-7445.AM2011-LB-160

Abstract 4317: Low dose arsenic-induced transient p53 inhibition: A novel strategy for chemotherapy protection

Abstract Because of its effectiveness in killing cancer cells, chemotherapy remains to be one of the common modalities for cancer treatment, but the resulting severe side effects often pose a significant threat to cancer patients. Recognizing p53 activation in the sensitive tissues as the primary mechanism for chemotherapy-induced acute toxicity and the universal p53 inactivation in human cancers, we exploited the use of low dose arsenic to inhibit p53 for a selective protection of normal tissues from chemotherapeutics-induced damages. Colon carcinoma cell line SW-480 was used to generate a mouse xenograft model. Treatments were initiated three weeks after implantation when the tumor size reached approximately 100 mm3. Arsenic pretreatment was carried out by feeding sex-matched mice (4-6 weeks of age) with water (1.0 mg/L) for three days. As expected, treatment of tumor-bearing mice with 5FU for 7 days resulted in 77% decrease in tumor volume when compared with the untreated group. The brief treatment with low doses of arsenic did not affect the ability of 5FU to induce tumor regression as evidenced by an 80% reduction of tumor size. However, arsenic treatment was associated with a marked alleviation of 5FU-induced systemic toxicity as demonstrated by the finding that arsenic pretreatment reduced 5FU-induced body weight loss from 25% to 4%. The protecting effect of arsenic was also clearly evident in reducing 5FU-induced damage in gastrointestinal (GI) track and hematopoietic (HP) system, two of the most sensitive tissues. Using mutant p53 expressing mice, we demonstrate that arsenic-mediated protection primarily depends on functional p53. Our preclinical study implicates that the brief use of low doses arsenic to inhibit p53 is an effective approach of chemotherapy protection. If successfully validated in clinical studies, this strategy may not only minimize side effects, but would also allow escalated therapeutic doses to improve treatment efficacy in a safe and effective approach for cancer therapy protection. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4317. doi:10.1158/1538-7445.AM2011-4317

Abstract 591: Expanding the therapeutic window through pharmacological activation of the RB pathway in breast cancer treatment

Abstract Triple negative breast cancer (TNBC) is a highly aggressive disease that is most often treated with cytotoxic chemotherapies, such as anthracyclines and platinum compounds. While effective for certain tumors, these therapies are known to cause severe toxicities in numerous tissues. Thus, targeting pathways to both exploit therapy-sensitive tumors and ameliorate tissue toxicity is of utmost significance. Loss of the retinoblastoma tumor suppressor (RB) protein is a frequent event in TNBC, and is expected to alter therapeutic sensitivity by perturbing cell cycle checkpoints and yielding a predilection towards cell death. Conversely, it is possible that the same principles that drive sensitivity to cytotoxic agents in an RB-deficient setting could be used to prevent toxicities in an RB-proficient setting (i.e. normal tissues). Thus, modulation of the RB pathway could be critical for expanding the therapeutic window in the treatment of breast cancer. To address this hypothesis, combination studies of pharmacological activation of the RB pathway and cytotoxic chemotherapies commonly used to treat TNBC were performed in vitro and in vivo. Results indicate that activation of the RB pathway can modulate the efficacy of cytotoxic compounds in the treatment of TNBC. The mechanisms behind these observations were attributed directly to RB-mediated regulation of DNA damage and repair signaling pathways, as well as apoptosis. RB-deficiency resulted in bypass of these mechanisms and thus enhanced sensitivity to cytotoxic therapies. These results were supported by in silico data demonstrating that RB-deficient TNBC is associated with better clinical outcome in response to chemotherapy. Importantly, functional studies indicated that RB pathway activation can provide protection against the toxicity of frequently used chemotherapeutic compounds in normal tissue. Combined, these studies suggest that RB pathway status could be utilized in the clinic to direct combination treatments that would exploit the sensitivity of RB-deficient tumors to cytotoxic chemotherapies while simultaneously providing protection for normal tissues. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 591. doi:10.1158/1538-7445.AM2011-591

Abstract 2610: Histone deacetylase inhibitors mediate pharmacological rescue of the ABCG2 Q141K variant: Potential for therapeutics in cancer and gout

Abstract ABCG2 is an ATP-binding cassette half-transporter that has garnered interest in pharmacogenomics as a modulator of oral drug absorption, drug excretion, and drug distribution through expression at the blood-brain barrier and the maternal-fetal barrier. A single nucleotide polymorphism (SNP) C421A in ABCG2, resulting in a glutamic acid to lysine mutation at amino acid 141 (Q141K), confers impaired protein expression and function. Pharmacogenomic studies have linked the SNP to increased exposure to substrate drugs including irinotecan, topotecan, sunitinib and gefitinib. Moreover, it has been shown that 10 % of gout cases can be attributed to the Q141K variant. We have studied the biology underlying altered expression and function of the ABCG2 variant. Q141K protein was resistant to degradation by Endo H, suggesting that it was fully processed and folded. Q141K ABCG2 expression was increased by the lysosome inhibitor bafilomycin, indicating that some of the protein reached the cell surface, although at reduced levels. But the largest fraction of the Q141K variant was retained in an intracellular compartment where a part was eliminated through the proteasomal pathway while the undegraded ABCG2 accumulated in the aggresomes, as shown by colocalization of the transporter with the centrosome marker, γ-tubulin. The ability of several agents to impact ABCG2 trafficking to the cell surface was evaluated. Mitoxantrone, an ABCG2 substrate previously noted to act as a pharmacological chaperone, induced a 2-fold increase in Q141K ABCG2 expression at the cell surface but only slightly enhanced ABCG2-related efflux. Romidepsin and other histone deacetylase inhibitors (HDIs), known to increase levels of ABCG2 mRNA, were also assayed. A significant increase in total protein, surface expression, and function was seen in Q141K ABCG2 variant when exposed to various HDIs. Immunofluorescence analysis by confocal microscopy showed a dramatic shift to the plasma membrane following exposure to the HDIs, whereas the localization of α-tubulin, HDAC6 and vimentin, involved in aggresome formation and structure, were unchanged. These results support the notion that Q141K ABCG2 variant is trapped in the aggresome and that HDIs aid localization to the surface. Some supplementary experiments showed that the Q141K ABCG2 states of phosphorylation, acetylation and dimerization were unmodified after HDIs treatment, and that the chaperones BiP, Hsp70 or Hsp90 were not involved in rescue. Investigations into the HDI-mediated mechanisms are underway. In addition to non-oncologic indications, the restoration of ABCG2 function has potential applications in oncology, in improving normal tissue protection and drug elimination, as well as in cancer prevention since several carcinogens are substrates for ABCG2. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2610. doi:10.1158/1538-7445.AM2011-2610

A Phase I Study of Concurrent Chemotherapy (Paclitaxel and Carboplatin) and Thoracic Radiotherapy with Swallowed Manganese Superoxide Dismutase Plasmid Liposome Protection in Patients with Locally Advanced Stage III Non-Small-Cell Lung Cancer

Manganese superoxide dismutase (MnSOD) is a genetically engineered therapeutic DNA/liposome containing the human MnSOD transgene. Preclinical studies in mouse models have demonstrated that the expression of the human MnSOD transgene confers protection of normal tissues from ionizing irradiation damage. This is a phase I study of MnSOD plasmid liposome (PL) in combination with standard chemoradiation in surgically unresectable stage III non-small-cell lung cancer. Chemotherapy (carboplatin and paclitaxel) was given weekly (for 7 weeks), concurrently with radiation. MnSOD PL was swallowed twice a week (total 14 doses), at three dose levels: 0.3, 3, and 30 mg. Dose escalation followed a standard phase I design. Esophagoscopy was done at baseline, day 4, and 6 weeks after radiation with biopsies of the squamous lining cells. DNA was extracted and analyzed by PCR for the detection of the MnSOD transgene DNA. Ten patients with AJCC stage IIIA (three) and IIIB (seven) completed the course of therapy. Five had squamous histology, two adenocarcinoma, one large cell, and two not specified. Patients were treated in three cohorts at three dose levels of MnSOD PL: 0.3 (three patients), 3 (three patients), and 30 mg (four patients). The median dose of radiation was 77.7 Gy (range 63-79.10 Gy). Overall response rate for the standard chemoradiation regimen was 70% (n = 10). There were no dose-limiting toxicities reported in all three dosing tiers. It is concluded that the oral administration of MnSOD PL is feasible and safe. The phase II recommended dose is 30 mg.

The effect of acetylsalicylic acid as a radioprotector

Ionizing radiation cell injury occurs by means of oxidative/ nitrosative stress mediators. Protection of normal tissues from damage might increase the therapeutic ratio. It is shown that acetylsalicylic acid (ASA), a member of the non-steroidal antiinflammatory group, can inhibit the release of prostaglandins that play a role in many forms of tissue damages and might prevent tissue/cell damages in various diseases with its similar anti-oxidant properties. With clinical/preclinical studies, it is demonstrated that ASA can reduce oxidative damage/injury and that it has a place in protection from cancer. It might be stated that it reduces radiation/irradiation-based geno-cytotoxicity. ASA is an agent that has not yet been used as a radioprotector in the clinic, and it is worth being supported with more advanced studies. In this examination, it is intended to discuss the current role of ASA as a radioprotector.

Hypothermia postpones DNA damage repair in irradiated cells and protects against cell killing

Hibernation is an established strategy used by some homeothermic organisms to survive cold environments. In true hibernation, the core body temperature of an animal may drop to below 0°C and metabolic activity almost cease. The phenomenon of hibernation in humans is receiving renewed interest since several cases of victims exhibiting core body temperatures as low as 13.7°C have been revived with minimal lasting deficits. In addition, local cooling during radiotherapy has resulted in normal tissue protection. The experiments described in this paper were prompted by the results of a very limited pilot study, which showed a suppressed DNA repair response of mouse lymphocytes collected from animals subjected to 7-Gy total body irradiation under hypothermic (13°C) conditions, compared to normothermic controls. Here we report that human BJ-hTERT cells exhibited a pronounced radioprotective effect on clonogenic survival when cooled to 13°C during and 12h after irradiation. Mild hypothermia at 20 and 30°C also resulted in some radioprotection. The neutral comet assay revealed an apparent lack on double strand break (DSB) rejoining at 13°C. Extension of the mouse lymphocyte study to ex vivo-irradiated human lymphocytes confirmed lower levels of induced phosphorylated H2AX (γ-H2AX) and persistence of the lesions at hypothermia compared to the normal temperature. Parallel studies of radiation-induced oxidatively clustered DNA lesions (OCDLs) revealed partial repair at 13°C compared to the rapid repair at 37°C. For both γ-H2AX foci and OCDLs, the return of lymphocytes to 37°C resulted in the resumption of normal repair kinetics. These results, as well as observations made by others and reviewed in this study, have implications for understanding the radiobiology and protective mechanisms underlying hypothermia and potential opportunities for exploitation in terms of protecting normal tissues against radiation.

TBI during BM and SCT: review of the past, discussion of the present and consideration of future directions

TBI has been used widely in the setting of BMT over the past 3 decades. Early research demonstrated feasibility and efficacy in the myeloablative setting, in preparation first for allogenic BMT and later for autologous stem cell rescue. As experience with TBI increased, its dual roles of myeloablation and immunosuppression came to be recognized. Toxicity associated with myeloablative TBI remains significant, and this treatment is generally reserved for younger patients with excellent performance status. Reduced intensity conditioning regimens may be useful to provide immunosuppression for patients who are not candidates for myeloablative treatment. Efforts to reduce toxicity through protection of normal tissue using methods of normal tissue blocking and use of TLI, rather than TBI, continue. In the future, modalities such as helical tomotherapy, proton radiotherapy and radioimmunotherapy, may have roles in delivery of radiation to the BM and lymphoid structures with reduced normal tissue toxicity. With further investigation, these efforts may expand the therapeutic ratio associated with TBI, allowing safer delivery to a broader range of patients.

Amifostine in the Treatment of Head and Neck Cancer: Intravenous Administration, Subcutaneous Administration, or None of the Above

Amifostine in the Treatment of Head and Neck Cancer: Intravenous Administration, Subcutaneous Administration, or None of the Above