Cytotoxicity and Radiosensitizing Potentials of Pilosulin-3, a Recombinant Ant Venom, in Breast Cancer Cells.

Venom peptides are promising agents in the development of unconventional anticancer therapeutic agents. This study explored the potential of Pilosulin-3, a recombinant peptide from the venom of the Australian jack jumper ant "Myrmecia pilosula", as a cytotoxic and radiosensitizing agent in MCF-7 and MDA-MB-231 breast cancer (BC) cell lines. Pilosulin-3's cytotoxicity was evaluated across a wide range of concentrations using a proliferation assay. Cell cycle progression and apoptosis were examined at the inhibitory concentration 25% (IC25) and IC50 of Pilosulin-3, both with and without a 4Gy X-ray irradiation dose. Radiosensitivity was assessed at IC25 using the clonogenic survival assay. The study revealed that Pilosulin-3 exerted a concentration-dependent cytotoxic effect, with IC25 and IC50 values of 0.01 and 0.5 µM, respectively. In silico screening indicated high selectivity of Pilosulin-3 peptide, which was predicted to be the most likely anticancer agent (PROB = 0.997) with low hemolytic activity (PROP = 0.176). Although Pilosulin-3 exhibited a significant (p < 0.05) G2/M cell cycle arrest in combination with radiation, there was no discernible effect on apoptosis induction or cell survival following irradiation. In conclusion, Pilosulin-3 proved to be cytotoxic to BC cells and induced a cytostatic effect (G2/M arrest) when combined with radiation. However, it did not enhance the efficacy of cell killing by irradiation. While it holds potential as a cytotoxic agent in breast cancer treatment, its application as a radiosensitizer does not find support in these results.

Establishing a Reference Dose-Response Calibration Curve for Dicentric Chromosome Aberrations to Assess Accidental Radiation Exposure in Saudi Arabia.

In cases of nuclear and radiological accidents, public health and emergency response need to assess the magnitude of radiation exposure regardless of whether they arise from disaster, negligence, or deliberate act. Here we report the establishment of a national reference dose-response calibration curve (DRCC) for dicentric chromosome (DC), prerequisite to assess radiation doses received in accidental exposures. Peripheral blood samples were collected from 10 volunteers (aged 20-40 years, median = 29 years) of both sexes (three females and seven males). Blood samples, cytogenetic preparation, and analysis followed the International Atomic Energy Agency EPR-Biodosimetry 2011 report. Irradiations were performed using 320 kVp X-rays. Metafer system was used for automated and assisted (elimination of false-positives and inclusion of true-positives) metaphases findings and DC scoring. DC yields were fit to a linear-quadratic model. Results of the assisted DRCC showed some variations among individuals that were not statistically significant (homogeneity test, P = 0.66). There was no effect of age or sex (P > 0.05). To obtain representative national DRCC, data of all volunteers were pooled together and analyzed. The fitted parameters of the radiation-induced DC curve were as follows: Y = 0.0020 (±0.0002) + 0.0369 (±0.0019) *D + 0.0689 (±0.0009) *D2. The high significance of the fitted coefficients (z-test, P < 0.0001), along with the close to 1.0 p-value of the Poisson-based goodness of fit (χ2 = 3.51, degrees of freedom = 7, P = 0.83), indicated excellent fitting with no trend toward lack of fit. The curve was in the middle range of DRCCs published in other populations. The automated DRCC over and under estimated DCs at low (<1 Gy) and high (>2 Gy) doses, respectively, with a significant lack of goodness of fit (P < 0.0001). In conclusion, we have established the reference DRCC for DCs induced by 320 kVp X-rays. There was no effect of age or sex in this cohort of 10 young adults. Although the calibration curve obtained by the automated (unsupervised) scoring misrepresented dicentric yields at low and high doses, it can potentially be useful for triage mode to segregate between false-positive and near 2-Gy exposures from seriously irradiated individuals who require hospitalization.

Appraisal of mechanisms of radioprotection and therapeutic approaches of radiation countermeasures.

Radiation countermeasures are radioprotective agents that reduce the harmful effects of ionizing radiation. They have wide range of applications extending from protection of normal tissues of cancer patients during radiotherapy to safeguard people aftermath of radiologic or nuclear accidents. Despite the screening of thousands of natural and synthetic compounds, only few found place in clinic with limited tolerance. Therefore, mechanistic understanding is essential in the development of more suitable and customized radiation countermeasure agents. This review focuses on the mechanisms of radioprotection imparted by these agents. Radioprotectors are diverse and act through widely varying mechanisms that can be classified in 10 categories: 1) scavenging of free radicals; 2) enhancing DNA repair; 3) synchronizing of cells; 4) modulating redox sensitive genes; 5) modulating growth factors and cytokines; 6) inhibiting apoptosis; 7) repurposing of drug; 8) interacting and chelating of radionuclides; and therapeutic methods of tissue regeneration such as 9) gene therapy; and 10) stem cell therapy. The most common mechanism of radioprotection is the scavenging of free radicals whereas, modulation of growth factors, cytokines and redox genes emerge as effective strategies. Gene and stem cell therapies as therapeutic radiation countermeasures are being developed and can be applied in the near future to minimize the side effects of radiation exposure through tissues regenerations. Thus, the management of radiation exposure may require a holistic multi-mechanistic approaches to achieve optimal radiation protection during radiotherapy of cancer patients and in cases of nuclear eventualities.

Genetic Predisposition to Cervical Cancer and the Association With XRCC1 and TGFB1 Polymorphisms.

OBJECTIVE: Cervical carcinoma (CC), a multifactorial cancer, is assumed to have a host genetic predisposition component that modulates its susceptibility in various populations. We investigated the association between CC risk in Saudi women and 6 single-nucleotide polymorphisms (SNPs) in hypothesis-driven candidate genes. METHODS: A total of 545 females were included, comprising 232 CC patients and 313 age-/sex-matched control subjects. Six SNPs (CDKN1A C31A, ATM G1853A, HDM2 T309G, TGFB1 T10C, XRCC1 G399A, and XRCC3 C241T) were genotyped by direct sequencing. RESULTS: Of the 6 SNPs studied, TGFB1 T10C (odds ratio, 0.74; 95% confidence interval, 0.57-0.94) and XRCC1 G399A (odds ratio, 1.45; 95% confidence interval, 1.11-1.90) displayed different frequencies in cancer patients and control subjects and showed statistically significant association in univariate (P = 0.017, P = 0.005, respectively) analysis. The Cochran-Armitage trend test had confirmed the results (P = 0.027 and P = 0.006, respectively), indicating an ordering in the effect of the risk alleles in CC patients. The 2 SNPs, TGFB1 T10C and XRCC1 G399A, showed also degrees of deviation from Hardy-Weinberg equilibrium in cancer patients (P = 0.001 and P = 0.083, respectively) but not in the control subjects. Furthermore, correction for multiple testing using multivariate logistic regression to assess the joint effect of all SNPs has sustained significant statistical association (P = 0.025 and P = 0.009, respectively). CONCLUSIONS: TGFB1 T10C and XRCC1 G399A SNPs were associated with CC risk in univariate and multivariate analysis and displayed allele-dosage effects and coselection in cancer patients. Patients harboring the majority allele TGFB1 T10 (Leu) or the variant allele XRCC1 399A (Gln) have approximately 1.5-fold increased risk to develop CC. Host SNPs genotyping may provide relevant biomarkers for CC risk assessment in personalized preventive medicine.

Reduced rate of human papillomavirus infection and genetic overtransmission of TP53 72C polymorphic variant lower cervical cancer incidence.

BACKGROUND: Cervical cancer is a predominantly human papillomavirus (HPV)-driven disease worldwide. However, its incidence is unexplainably low in western Asia, including Saudi Arabia. Using this paradigm, we investigated the role of HPV infection rate and host genetic predisposition in TP53 G72C single nucleotide polymorphism (SNP) presumed to affect cancer incidence. METHODS: Patients treated between 1990 and 2012 were reviewed, and a series of 232 invasive cervical cancer cases were studied and compared with 313 matched controls without cancer. SNP was genotyped by way of direct sequencing. HPV linear array analysis was used to detect and genotype HPV in tumor samples. RESULTS: The incidence of cervical cancer revealed bimodal peaks at 42.5 years, with a slighter rebound at 60.8 years. Among all cases, 77% were HPV-positive and 16 HPV genotypes were detected-mostly genotypes 16 (75%) and 18 (9%)-with no difference by age, histology, or geographical region. Although the TP53 G72C genotype was not associated with overall cervical cancer risk, it was significantly associated with HPV positivity (odds ratio, 0.57; 95% confidence interval, 0.36-0.90; P = .016). Furthermore, the variant C allele was significantly overtransmitted in the population (P < .0003). CONCLUSION: Cervical cancer incidence displays bimodal curve peaking at a young age with secondary rebound at older age. The combination of relative low HPV infection and variant TP53 72C allele overtransmission provide a plausible explanation for the low incidence of cervical cancer in our population. Therefore, HPV screening and host SNP genotyping may provide more relevant biomarkers to gauge the risk of developing cervical cancer. Cancer 2017;123:2459-66. © 2017 American Cancer Society.

Involvement of single-nucleotide polymorphisms in predisposition to head and neck cancer in Saudi Arabia.

AIM: Individuals differ in their inherited tendency to develop cancer. This has been suggested to be due to genetic variations between individuals. Single-nucleotide polymorphisms (SNPs) are the most common form of genetic variations found in the human population. The aim of this study was to investigate the association between 10 SNPs in genes involved in cell cycle control and DNA repair (p21 C31A, p53 G72C, ATM G1853A, XRCC1 G399A, XRCC3 C241T, Ku80 A2790G, DNA Ligase IV C9T, DNA-PKcs A3434G, TGF-beta T10C, MDM2 promoter T309G) and the risk to develop head and neck cancer. MATERIALS AND METHODS: A cohort of 407 individuals (156 cancer patients and 251 controls) was included. DNA was extracted from peripheral blood. SNPs were genotyped by direct sequencing. RESULTS: Data showed significant allelic associations for p21 C31A (p=0.04; odds ratio [OR]=1.44; confidence interval [CI]: 1.02-2.03), Ku80 A2790G (p=0.04; OR=1.5; CI: 1.01-2.23), and MDM2 T309G (p=0.0003; OR=0.58; CI: 0.43-0.78) and head and neck cancer occurrence. Both cancer cases and controls were in Hardy-Weinberg equilibrium. CONCLUSION: SNPs can be associated with head and neck cancer in the Saudi population. The p21 C31A, Ku80 A2790G, and MDM2 T309G SNPs could be used as genetic biomarkers to screen individuals at high cancer risk.

Involvement of mitochondrial DNA sequence variations and respiratory activity in late complications following radiotherapy.

PURPOSE: Mitochondria and ionizing radiation overlap in a number of features; for instance, both generate harmful reactive oxygen species, and that radiation can induce cell death through the intermediary of mitochondria. Because a number of genetic variations in nuclear genes are frequently associated with response to cancer treatment, the aim of this case-control study was to test the hypothesis that mitochondrial DNA (mtDNA) genetic variations can contribute to patient-to-patient variability in normal tissue response to radiotherapy. EXPERIMENTAL DESIGN: Thirty-two nasopharyngeal carcinomas patients treated with definitive radiotherapy were included. The grade (G) of s.c. and deep tissue fibrosis was scored according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer grading system. Coding and RNA mtDNA (between 611 and 15,978 bp) were sequenced, and genetic variations were scored. Mitochondrial respiratory activity was measured by resazurin reduction assay. RESULTS: Data showed a significantly (P = 0.003) higher number of nonsynonymous genetic variations in the radiosensitive (G(2)-G(3); 16 patients) as compared with the control (G(0)-G(1); 16 patients) groups. The nonsynonymous A10398G variation in the ND3 gene was significantly associated with fibrotic reaction (P = 0.01). The radiosensitive patients had a 7-fold (95% confidence interval, 1.16-51.65) higher risk of developing moderate to severe fibrosis (G(2)-G(3)) following radiotherapy. This was significantly correlated with lower mitochondrial respiratory activity (P = 0.001). CONCLUSION: Mitochondria contribute to radiation sensitivity, and genetic variations can be associated with late reactions to radiotherapy. Predictive markers of radiosensitivity should take into account mtDNA genetic variations in addition to variations in nuclear genes.