Abstract SSY01-03: An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer

Introduction:

Head and neck cancer (HNC) is a challenging disease due to its heterogeneity and complexity. Despite continued advances in therapeutic options, treatment-associated toxicities and overall clinical outcomes have remained disappointing. Even with radiation therapy (RT), which remains the primary curative modality for HNC, the most effective regimens achieve local control rates of 50-70%, with disease free survival rates of only 30-40% for patients with locally advanced HNSCC. Thus, the development of novel strategies to enhance tumor cell killing, while minimizing damage to the surrounding normal tissues, is critical for improving cure rates with RT.

Methods:

A siRNA-based high-throughput screen (HTS) was performed for the large-scale identification of novel genes that will selectively sensitize HNC cells to ionizing radiation (IR). The Dharmacon Protein Kinase and Druggable Genome siRNA Libraries were screened using FaDu cells (human hypopharyngeal squamous cell cancer). Radiosensitizing targets were subjected to functional validation studies and in vitro characterization of mechanisms for radiosensitization. In vivo validation studies including tumor formation assays and the treatment of established HNC xenograft models were also conducted.

Results:

The HTS identified 67 target sequences with potential radiosensitizing effects; the validity of the screen was corroborated by the identification of known radiosensitizing targets (e.g. ATM, ATR, AURKA). Targets reducing the surviving fraction by >50% at 2 Gy relative to their un-irradiated counterparts were selected for further evaluation. A key regulator of the heme biosynthetic pathway was thus identified as a novel tumor-selective radiosensitizing target. Down-regulation of the enzyme plus IR induced caspase-mediated apoptosis and cell cycle arrest in vitro, while delaying tumor growth in vivo. Radiosensitization appeared to be mediated via enhancement of tumor oxidative stress from perturbation of iron homeostasis and increased reactive oxygen species production. This radiosensitizing target was significantly over-expressed in HNC patient biopsies, wherein lower pre-RT mRNA levels correlated with improved survival, suggesting that this enzyme could also be a potential predictor for radiation response. Down-regulation of the enzyme also radiosensitized several different human cancer models, while sparing normal cells.

Conclusion:

We have successfully developed an RNAi-based radiosensitizer HTS, and uncovered a key regulator of heme biosynthesis as a potent sensitizer for RT, with potentially broad implications in the management of many human malignancies.

Citation Format: Emma Ito, Shijun Yue, Eduardo H. Moriyama, Angela B. Hui, Inki Kim, Wei Shi, Nehad M. Alajez, Nirmal Bhogal, GuoHua Li, Alessandro Datti, Aaron D. Schimmer, Brian C. Wilson, Peter P. Liu, Daniel Durocher, Benjamin G. Neel, Brian O'Sullivan, Bernard Cummings, Rob Bristow, Fei-Fei Liu. An RNAi screen identifies a heme biosynthetic mediator as a novel radiosensitizing target for head and neck cancer [abstract]. In: Proceedings of the AACR 101st Annual Meeting 2010; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr SSY01-03

A low-risk ZnT-8 allele (W325) for post-transplantation diabetes mellitus is protective against cyclosporin A-induced impairment of insulin secretion

SLC30A8 encodes the β-cell-specific zinc transporter-8 (ZnT-8) expressed in insulin secretory granules. The single-nucleotide polymorphism rs13266634 of SLC30A8 is associated with susceptibility to post-transplantation diabetes mellitus (PTDM). We tested the hypothesis that the polymorphic residue at position 325 of ZnT-8 determines the susceptibility to cyclosporin A (CsA) suppression of insulin secretion. INS (insulinoma)-1E cells expressing the W325 variant showed enhanced glucose-stimulated insulin secretion (GSIS) and were less sensitive to CsA suppression of GSIS. A reduced number of insulin granule fusion events accompanied the decrease in insulin secretion in CsA-treated cells expressing ZnT-8 R325; however, ZnT-8 W325-expressing cells exhibited resistance to the dampening of insulin granule fusion by CsA, and transported zinc ions into secretory vesicles more efficiently. Both tacrolimus and rapamycin caused similar suppression of GSIS in cells expressing ZnT-8 R325. However, cells expressing ZnT-8 W325 were resistant to tacrolimus, but not to rapamycin. The Down's syndrome candidate region-1 (DSCR1), an endogenous calcineurin inhibitor, overexpression and subsequent calcineurin inhibition significantly reduced GSIS in cells expressing the R325 but not the W325 variant, suggesting that differing susceptibility to CsA may be due to different interactions with calcineurin. These data suggest that the ZnT-8 W325 variant is protective against CsA-induced suppression of insulin secretion. Tolerance of ZnT-8 W325 to calcineurin activity may account for its protective effect in PTDM.

Meal size and starch content affect gastric emptying in horses

REASONS FOR PERFORMING STUDY

Feeding practices have been associated with colic in horses. If meal size and composition have an effect on gastric emptying, this could be one of the mechanisms by which feeding practices are related to the occurrence of colic.

OBJECTIVES

To evaluate the effect of meal size and starch content on solid phase gastric emptying.

METHODS

Solid phase gastric emptying of 3 different radiolabelled meals, small low-starch (SmLS), small high-starch (SmHS) and large high-starch (LgHS) meals, was measured in 5 horses by scintigraphy using 99mTc-disofenin. Data were compared among meals using nonlinear mixed-effects models and paired t tests.

RESULTS

On a percentage basis, SmHS emptied significantly faster than LgHS and SmLS emptied significantly faster than SmHS meals. However, when meals of unequal size were compared by emptying rate in g/min and Kcal/min, LgHS emptied significantly faster than SmHS.

CONCLUSIONS

Meal size and composition affect gastric emptying.

POTENTIAL RELEVANCE

Further work needs to be performed in order to substantiate the possibility of a relationship between digestive functions and occurrence of colic and gastric ulcers.

Genetic associations of LYN with systemic lupus erythematosus

We targeted LYN, a src-tyosine kinase involved in B-cell activation, in case-control association studies using populations of European-American, African-American and Korean subjects. Our combined European-derived population, consisting of 2463 independent cases and 3131 unrelated controls, shows significant association with rs6983130 in a female-only analysis with 2254 cases and 2228 controls (P=1.1 x 10(-4), odds ratio (OR)=0.81 (95% confidence interval: 0.73-0.90)). This single nucleotide polymorphism (SNP) is located in the 5' untranslated region within the first intron near the transcription initiation site of LYN. In addition, SNPs upstream of the first exon also show weak and sporadic association in subsets of the total European-American population. Multivariate logistic regression analysis implicates rs6983130 as a protective factor for systemic lupus erythematosus (SLE) susceptibility when anti-dsDNA, anti-chromatin, anti-52 kDa Ro or anti-Sm autoantibody status were used as covariates. Subset analysis of the European-American female cases by American College of Rheumatology classification criteria shows a reduction in the risk of hematological disorder with rs6983130 compared with cases without hematological disorders (P=1.5 x 10(-3), OR=0.75 (95% CI: 0.62-0.89)). None of the 90 SNPs tested show significant association with SLE in the African American or Korean populations. These results support an association of LYN with European-derived individuals with SLE, especially within autoantibody or clinical subsets.

Generation of Mie size microdroplet aerosols with applications in laser-driven fusion experiments

We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti:Al2O3 laser focused to 2 x 10(19) W/cm2 was used to irradiate heavy water (D2O) aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2 x 10(3) fusion neutrons measured per joule of incident laser energy.

Impact of the income-based health service types on survival in patients with metastatic gastric cancer

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Background: Subscription to National Health Insurance (NHI) is a national obligation for South Korean people. For low-income citizens (about lower 3% of population), Medicaid is applied. Many recipients of Medicaid are vulnerable people such as old age singles, the homeless or the handicapped. These populations are suspected to have worse prognosis. According to one report, on the other hand, patients with Medicaid were more likely to receive chemotherapy than patients with NHI despite the uniform health insurance coverage within the two types of health cost financing. Owing to these conflicting findings, we investigated the relationship between health insurance type and prognosis. Methods: Patients are stage IV advanced gastric cancer patients who received palliative chemotherapy. Medical records were reviewed from January 2006 to November 2008 in Seoul Medical Center (municipal teaching hospital). Results: Total 37 patients were found. Median age was 61 years (range 31–85) and male constituted 75.7%. Platinum (cisplatin or oxaliplatin) combined with 5-FU was the most frequently used regimen (78.4%). Twelve patients (32.4%) were recipients of Medicaid. Median PFS and OS of NHI group were 6.9 (95% CI, 1.7–12.0) and 7.8 (95% CI, 3.4–12.1). And that of Medicaid were 5.6 (95% CI, 2.6–8.6) and 7.8 (95% CI, 3.4–12.2) months. The difference from two groups were not statistically different (p = 0.739 for PFS and 0.466 for OS). When patients were divided into longer or shorter survivors according to mean OS (14.1 ±2.6 months), NHI recipients had more probability for survival (odds ratio 0.72, 95% CI 0.56–0.92). Conclusions: The question is raised whether recipients of Medicaid have poorer prognosis than patients with NHI in metastatic gastric cancer in South Korea. Although it seems that NHI recipients has better prognosis, still we cannot sure. It should be cleared in large scale cohort study whether this is related to low socio-economic status or other uncontrolled confounder.

No significant financial relationships to disclose.

The clinical significance of oophorectomy in gastric patients

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Background: The oophorectomy in isolated metastasis of ovary can lead to long term survival in patients with gastric cancer, but the clinical significance of oophorectomy in stage IV gastric cancer patients is not known well in this time. Methods: We reviewed the medical record of the 55 gastric cancer patients who were metastasis or recurrent in ovary at Dongsan Medical Center, Kimyung University School of Medicine, Daegu, Korea from 1985 to 2008. Results: Twenty-one patients were metastasis to ovary at the time of diagnosis of gastric cancer, and 34 patients were recurrent in ovary after the gastric resection. The mean age was 45.3 ± 11.6 years in metastatic cancer and 46.8 ±12.6 years in recurrent cancer patients. The stage at the time of gastric resection in 34 recurrent patients were I in 3, II in 1, III in 18, and IV in 10. Adjuvant chemotherapy were performed in 26 (76.5%) patients. Oophorectomy were performed in 33 (97.1%) of recurrent cancer, and 17 (81.0%) of metastatic cancer. The 1-year and 2-year survival rate of metastatic cancer were 14.7%, and 0%, and 1-year, 2-year, and 3-year survival rate of recurrent cancer were 47.2%, 18.1%, and 0%, respectively. The median survival duration of metastatic cancer were 8.9 ±1.0 months, and recurrent cancer were 11.4 ±2.3 months. Recurrent cancer were better survival than metastatic cancer patients (p=0.014). The long-term survival (over 2 years) was noted in 5 patients of recurrent cancer patients. The stage of gastric cancer was correlated to overall survival time in total patients (p=0.028). But, the relapse-free survival time after gastrectomy is the only factor to predict survival duration after oophorectomy in recurrent cancer patients (p=0.029). Age, stage of gastric cancer, extent of involvement of ovary, and systemic chemotherapy were not related to survival time of recurrent cancer patients. Conclusions: The survival time in patients with oophorectomy in recurrent gastric cancer was correlated to relapse-free survival time after gastric resection.

No significant financial relationships to disclose.

Prognostic significance of histological grade in clear-cell carcinoma of the ovary: a retrospective study of Korean Gynecologic Oncology Group

BACKGROUND

This study was to investigate the prognostic significance of clinicopathologic characteristics in patients with clear-cell carcinoma (CCC) of the ovary.

MATERIALS AND METHODS

Two hundred and one patients with CCC of the ovary were registered in the Korean Gynecologic Oncology Group. The Korean Gynecologic Pathology Study Group reviewed the pathological slides centrally, using a universal grading system. The prognostic significances of clinicopathologic factors were evaluated by multivariate analysis.

RESULTS

Most of the patients were diagnosed at an early stage (stage I, 61.3%), and the overall 5-year survival rate was 57%. Early-stage disease showed a favorable prognosis, but advanced diseases showed poor prognosis. Stage of disease was the only significant prognostic factor on multivariate analysis (P < 0.001). However, universal grade and residual tumor also showed prognostic significance on the forward stepwise likelihood ratio test. There was no survival difference observed between patients treated with paclitaxel-based and those treated with platinum-based combination chemotherapy.

CONCLUSIONS

The stage, residual tumor, and universal grade were significant prognostic factors in patients with CCC of the ovary. The universal grading system is applicable in determining prognosis of CCC of the ovary. Further clinical trials for optimal chemotherapy are in need.

High-strength nitrogenous wastewater treatment in biofilm and granule anammox processes

Biofilm and granule reactors were employed to remove nitrogen via an anammox reaction applying synthetic nitrogen wastewater, whose concentration was in the range of 20 to 1,400 mg N/L as total nitrogen. A biofilm reactor was packed with non-woven fabric and a granule reactor was filled with anaerobic granular sludge taken from the brewery wastewater treatment plant. Both reactors were seeded with Planctomycetes KSU-1 and operated for 450 days. The biofilm reactor showed high NH(4) (+)-N and NO(2) (-)-N removal efficiencies of over 88% and 94%, respectively, until total nitrogen concentration was reached at 800 mg N/L. However, the biofilm reactor showed severe inhibition at over 1,000 mg N/L of total nitrogen due to nitrogen overloading. The granule reactor revealed better nitrogen removal performance than the biofilm reactor, showing high NH(4) (+)-N and NO(2) (-)-N removal efficiencies of over 90%, even at a total nitrogen concentration of 1,400 mg N/L. However, aggregation of anammox bacteria grown in the sludge bed after long-term operation resulted in the deterioration of nitrogen. The removal ratio of NH(4) (+)-N and NO(2) (-)-N was close to 1:1, suggesting other reactions related to ammonium oxidation could occur simultaneously. Free ammonia inhibition as well as NO(2) (-)-N could be significant when high-strength nitrogenous wastewater was applied.

Fluoresceinated peanut agglutinin (PNA) is a marker for live O(2) sensing glomus cells in rat carotid body

Experiments using live dissociated carotid body (CB) cells for patch clamping, [Ca(++)](i) or other measurements require positive identification of the cell being recorded. At present, cell morphology is usually employed, but several cell types within the carotid body evidence similar morphologic characteristics. Therefore, we sought to develop a method utilizing a vital dye to identify glomus cells before and during experiments that require live cells, such as patch clamp studies. It was previously reported that the binding sites for peanut agglutinin (PNA) were highly expressed by all neuroendocrine-derivatives of the sympathoadrenal neural crest, including glomus cells, small, intensely fluorescent cells, PC-12 cells, and adrenal chromaffin cells in situ (katz et al. 1995). By utilizing the binding characteristics of galactose-specific lectin peanut agglutinin (PNA) on the outer cell membrane, we tested the possibility that the fluoresceinated PNA may preferentially bind to CB glomus cells. The results to date show: (1) Rhodamine tagged PNA (Rhod-PNA) binds to the live dissociated glomus cells in less than one hour incubation and can be visualized in superfused cells; (2) Rhod-PNA labeled cells are perfectly matched with tyrosine hydroxylase (TH) positive glomus cells; (3) Rhod-PNA did not interfere with Fura-2 for Ca(++) imaging; (4) Rhod-PNA bound to glomus cells in [Ca(++)](i) studies does not affect O(2) response of glomus cells. Thus fluoresceinated PNA may be a useful marker for live CB glomus studies, without adversely affecting their physiologic response.

Cell death and endoplasmic reticulum stress: disease relevance and therapeutic opportunities

The accumulation of unfolded proteins in the endoplasmic reticulum (ER) represents a cellular stress induced by multiple stimuli and pathological conditions. These include hypoxia, oxidative injury, high-fat diet, hypoglycaemia, protein inclusion bodies and viral infection. ER stress triggers an evolutionarily conserved series of signal-transduction events, which constitutes the unfolded protein response. These signalling events aim to ameliorate the accumulation of unfolded proteins in the ER; however, when these events are severe or protracted they can induce cell death. With the increasing recognition of an association between ER stress and human diseases, and with the improved understanding of the diverse underlying molecular mechanisms, novel targets for drug discovery and new strategies for therapeutic intervention are beginning to emerge.