Silibinin Preferentially Radiosensitizes Prostate Cancer by Inhibiting DNA Repair Signaling

High-definition FT-IR reveals a synergistic effect on lipid accumulation in prostate cancer cells induced by a combination of X-rays and radiosensitizing drugs

Radiotherapy is one of the most commonly used cancer therapies with many benefits including low toxicity to healthy tissues. However, a major problem in radiotherapy is cancer radioresistance. To enhance the effect of this kind of therapy several approaches have been proposed such as the use of radiosensitizers. A combined treatment of radiotherapy and radiosensitizing drugs leads to a greater effect on cancer cells than anticipated from the addition of both responses (synergism). In this study, high-definition FT-IR imaging was applied to follow lipid accumulation in prostate cancer cells as a response to X-ray irradiation, radiosensitizing drugs, and a combined treatment of X-rays and the drugs. Lipid accumulation induced in the cells by an increasing X-ray dose and the presence of the drugs was analyzed using Principal Component Analysis and lipid staining. Finally, the synergistic effect of the combined therapy (X-rays and radiosensitizers) was confirmed by calculations of the integral intensity of the 2850 cm-1 band.

Simulated microgravity induces DNA damage concurrent with impairment of DNA repair and activation of cell-type specific DNA damage response in microglial and glioblastoma cells

Long-term spaceflights affect the structural changes in brain, alter motor or cognitive function and associated development of neuro-optic syndrome in astronauts. Studies addressing the impact of microgravity on brain cells are very limited. Herein, we employed microglial (CHME3) and glioblastoma (U87MG and A172) cells to study their molecular and functional adaptations under simulated microgravity (SMG) exposure. A reduction in cell viability and proliferation with decreased levels of PCNA were observed in these cells. SMG caused extensive DNA damage with an increase in γH2A.X (ser139) phosphorylation and differential activation/expression of DNA damage response (DDR) proteins including ATM, ATR, Chk1, Chk2 and p53 in all the three cell lines. Unlike CHME3, the ATM/Chk2-dependent DDR pathway was activated in glioblastoma cells suggesting a marked difference in the adaptation between normal and cancer cells to SMG. Five different classes of DNA repair pathways including BER, NER, MMR, NHEJ and HR were suppressed in both cell lines with the notable exception of NHEJ (Ku70/80 and DNA-PK) activation in U87MG cells. SMG induced mitochondrial apoptosis with increased expression of Bax, cleaved caspase-3 and cleaved poly-(ADP-ribose) polymerase, and reduced Bcl-2 level. SMG triggered apoptosis simultaneously via ERK1/2 and AKT activation, and inhibition of GSK3β activity which was reversed by MEK1 and PI3K inhibitors. Taken together, our study revealed that microgravity is a strong stressor to trigger DNA damage and apoptosis through activation of ERK1/2 and AKT, and impairment of DNA repair capacity, albeit with a cell-type difference in DDR and NHEJ regulation, in microglial and glioblastoma cells.

Role of heat shock protein 70 in silibinin-induced apoptosis in bladder cancer

Hsp70 (heat shock protein 70) plays critical roles in cancer cell proliferation and apoptosis. Recently, accumulating evidences have demonstrated the cancer promoting effects of Hsp70 in bladder cancer. The development of novel therapeutic approaches targeting Hsp70 thus received great attention from researchers. In this study, we demonstrated that silibinin, a natural polyphenolic flavonoid isolated from the milk thistle, targeted Hsp70 by inhibiting its transcription in bladder cancer cells. We also demonstrated that knockdown of endogenous Hsp70 enhanced silibinin-induced apoptosis, while overexpression of exogenous Hsp70 could partially reverse the effects of silibinin-induced cell apoptosis. Furthermore, we found that silibinin could activate HSF1/Hsp70-regulated mitochondrial apoptotic pathway. Mechanically, silibinin inhibited the interaction between Apaf-1 and Hsp70, thus increasing the recruitment of pro caspase-9. Results from in vivo study demonstrated that silibinin suppressed the growth of bladder cancer xenografts, which was accompanied with the activation of caspase-3 and downregulation of HSF1 and Hsp70. Taken together, our data indicates that silibinin induces mitochondrial apoptosis via inhibiting HSF1/Hsp70 pathway and also suggests the therapeutic potential of silibinin in the treatment of bladder cancer.

Silibinin Radiosensitizes EGF Receptor-knockdown Prostate Cancer Cells by Attenuating DNA Repair Pathways

Emergence of radioresistance in prostate cancer (PCa) cells is a major obstacle in cancer therapy and contributes to the relapse of the disease. EGF receptor (EGFR) signaling plays an important role in the development of radioresistance. Herein, we have assessed the modulatory effects of silibinin on radiation-induced resistance via DNA repair pathways in EGFR-knockdown DU145 cells. shRNA-based silencing of EGFR was done in radioresistant human PCa DU145 cells and effects of ionizing radiation (IR) and silibinin were assessed using clonogenic and trypan blue assays. Furthermore, radiosensitizing effects of silibinin on PCa in context with EGFR were analyzed using flow cytometry, comet assay, and immunoblotting. Silibinin decreased the colony formation ability with an increased death of DU145 cells exposed to IR (5 Gray), with a concomitant decrease in Rad51 protein expression. Silibinin (25 μM) augmented the IR-induced cytotoxic effect in EGFR-knockdown PCa cells, along with induction of G2/M phase cell cycle arrest. Further, we studied homologous recombination (HR) and non-homologous end joining (NHEJ) pathways in silibinin-induced DNA double-strand breaks in EGFR-knockdown DU145 cells. Silibinin down-regulated the expression of Rad51 and DNA-dependent protein kinase proteins without any considerable effect on Ku70 and Ku80 in IR-exposed EGFR-knockdown PCa cells. The pro-survival signaling proteins, phospho-extracellular signal-regulated kinases (ERK)1/2, phospho-Akt and phospho-STAT3 were decreased by silibinin in EGFR-deficient PCa cells. These findings suggest a novel mechanism of silibinin-induced radiosensitization of PCa cells by targeting DNA repair pathways, HR and NHEJ, and suppressing the pro-survival signaling pathways, ERK1/2, Akt and STAT3, in EGFR-knockdown PCa cells.

BNIP3 contributes to silibinin-induced DNA double strand breaks in glioma cells via inhibition of mTOR

BNIP3 is found to eliminate cancer cells via causing mitochondrial damage and endoplasmic reticulum stress, but it remains elusive of its role in regulating DNA double strand breaks (DSBs). In this study, we find that silibinin triggers DNA DSBs, ROS accumulation and expressional upregulation of BNIP3 in glioma cells. Mitigation of ROS with antioxidant GSH significantly inhibits silibinin-induced DNA DSBs and glioma cell death. Then, we find knockdown of BNIP3 with SiRNA obviously prevents silibinin-induced DNA DSBs and ROS accumulation. Mechanistically, BNIP3 knockdown not only reverses silibinin-triggered depletion of cysteine and GSH via maintaining xCT level, but also abrogates catalase decrease. Notably, silibinin-induced dephosphorylation of mTOR is also prevented when BNIP3 is knocked down. Given that activated mTOR could promote xCT expression and inhibit autophagic degradation of catalase, our data suggest that BNIP3 contributes to silibinin-induced DNA DSBs via improving intracellular ROS by inhibition of mTOR.

EGFR-mediated Rad51 expression potentiates intrinsic resistance in prostate cancer via EMT and DNA repair pathways

AIM

To study the role of EGFR signaling in regulation of intrinsic resistance in prostate cancer.

MATERIALS AND METHODS

Radioresistant prostate carcinoma DU145 and PC-3 cells were used to study the effect of shRNA-mediated knockdown of EGFR on intrinsic radioresistance mechanisms. Semi-quantitative PCR, western blotting, growth kinetics, colony formation, transwell migration, invasion and trypan blue assays along with inhibitors erlotinib, NU7441, B02, PD98059 and LY294002 were used.

KEY FINDINGS

EGFR knock-down induced morphological alterations along with reduction in clonogenic potential and cell proliferation in DU145 cells. Migratory potential of prostate cancer cells were reduced concomitant with upregulation of epithelial marker, E-cadherin and decreased expression of mesenchymal markers, vimentin and snail. Further, EGFR knock-down decreased the expression of Rad51 and DNA-PK at mRNA as well as protein levels. Likewise, erlotinib, an EGFR inhibitor, and NU7441, a DNA-PK inhibitor increased the expression of E-cadherin and decreased the level of vimentin. Both these inhibitors also decreased the levels of DNA damage regulatory protein Rad51. Further, Rad51 inhibitor, B02, inhibited the clonogenic potential, cell migration and reduced the expression of vimentin, Ku70 and Ku80, and also, B02 radiosensitized DU145 cells. EGFR-regulated expression of Rad51 was found to be mediated via PI3K/Akt and Erk1/2 pathways.

SIGNIFICANCE

EGFR was found to regulate DNA damage repair, survival and EMT responses in prostate cancer cells through transcriptional regulation of Rad51. A novel role of EGFR-Erk1/2/Akt-Rad51 axis through modulation of EMT and DNA repair pathways in prostate cancer resistance mechanisms is suggested.

Simulated microgravity triggers DNA damage and mitochondria-mediated apoptosis through ROS generation in human promyelocytic leukemic cells

The weightlessness or microgravity, a physical factor in space, may adversely affect the health of the space travellers or astronauts. The knowledge about the effect of microgravity on human cancer cells is very limited and poorly understood. Here, we employed rotary cell culture system (RCCS) to induce simulated microgravity (SMG) and examined its effects on human promyelocytic leukemic HL-60 cells. These cells were grown in normal gravity condition (1g) for control purpose. The 72 h exposure of cells to SMG decreased cell proliferation and viability which were accompanied by the reduced expression of PCNA and phosphorylated ERK1/2 and AKT proteins. SMG increased the DNA damage as well as the expression of DNA damage sensing proteins including ATM, ATR, Chk1, Chk2 and γH2A.X. The expression of AP1, XRCC1 and APEX1 regulating BER, XPC regulating NER and MLH1 and PMS2 regulating MMR were downregulated. However, SMG increased the expression of Ku70/80, DNA-PK and Rad51, regulating NHEJ and HR. SMG induced apoptosis and increased the levels of cleaved-poly-(ADP-ribose) polymerase and cleaved-caspase-3. An increase in Bax/Bcl-2 ratio and dissipation of mitochondrial membrane potential were also observed. SMG enhanced reactive oxygen species (ROS) formation which led to the enhanced DNA damage and apoptotic cell death. Overall, SMG induced ROS, DNA damage and differential expression of DNA repair genes, and altered the overall DNA repair capacity which may activate ATM/ATR-Chk1/2 and Ku70/80 and DNA-PK-mediated apoptotic cell death.

Revisiting prostate cancer metabolism: From metabolites to disease and therapy

Prostate cancer (PCa), one of the most commonly diagnosed cancers worldwide, still presents important unmet clinical needs concerning treatment. In the last years, the metabolic reprogramming and the specificities of tumor cells emerged as an exciting field for cancer therapy. The unique features of PCa cells metabolism, and the activation of specific metabolic pathways, propelled the use of metabolic inhibitors for treatment. The present work revises the knowledge of PCa metabolism and the metabolic alterations that underlie the development and progression of the disease. A focus is given to the role of bioenergetic sources, namely, glucose, lipids, and glutamine sustaining PCa cell survival and growth. Moreover, it is described as the action of oncogenes/tumor suppressors and sex steroid hormones in the metabolic reprogramming of PCa. Finally, the status of PCa treatment based on the inhibition of metabolic pathways is presented. Globally, this review updates the landscape of PCa metabolism, highlighting the critical metabolic alterations that could have a clinical and therapeutic interest.

Targeting DNA Damage Response in Prostate and Breast Cancer

Steroid hormone signaling induces vast gene expression programs which necessitate the local formation of transcription factories at regulatory regions and large-scale alterations of the genome architecture to allow communication among distantly related cis-acting regions. This involves major stress at the genomic DNA level. Transcriptionally active regions are generally instable and prone to breakage due to the torsional stress and local depletion of nucleosomes that make DNA more accessible to damaging agents. A dedicated DNA damage response (DDR) is therefore essential to maintain genome integrity at these exposed regions. The DDR is a complex network involving DNA damage sensor proteins, such as the poly(ADP-ribose) polymerase 1 (PARP-1), the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the ataxia-telangiectasia-mutated (ATM) kinase and the ATM and Rad3-related (ATR) kinase, as central regulators. The tight interplay between the DDR and steroid hormone receptors has been unraveled recently. Several DNA repair factors interact with the androgen and estrogen receptors and support their transcriptional functions. Conversely, both receptors directly control the expression of agents involved in the DDR. Impaired DDR is also exploited by tumors to acquire advantageous mutations. Cancer cells often harbor germline or somatic alterations in DDR genes, and their association with disease outcome and treatment response led to intensive efforts towards identifying selective inhibitors targeting the major players in this process. The PARP-1 inhibitors are now approved for ovarian, breast, and prostate cancer with specific genomic alterations. Additional DDR-targeting agents are being evaluated in clinical studies either as single agents or in combination with treatments eliciting DNA damage (e.g., radiation therapy, including targeted radiotherapy, and chemotherapy) or addressing targets involved in maintenance of genome integrity. Recent preclinical and clinical findings made in addressing DNA repair dysfunction in hormone-dependent and -independent prostate and breast tumors are presented. Importantly, the combination of anti-hormonal therapy with DDR inhibition or with radiation has the potential to enhance efficacy but still needs further investigation.

Epithelial to Mesenchymal Transition: A Mechanism that Fuels Cancer Radio/Chemoresistance

Epithelial to mesenchymal transition (EMT) contributes to tumor progression, cancer cell invasion, and therapy resistance. EMT is regulated by transcription factors such as the protein products of the SNAI gene family, which inhibits the expression of epithelial genes. Several signaling pathways, such as TGF-beta1, IL-6, Akt, and Erk1/2, trigger EMT responses. Besides regulatory transcription factors, RNA molecules without protein translation, micro RNAs, and long non-coding RNAs also assist in the initialization of the EMT gene cluster. A challenging novel aspect of EMT research is the investigation of the interplay between tumor microenvironments and EMT. Several microenvironmental factors, including fibroblasts and myofibroblasts, as well as inflammatory, immune, and endothelial cells, induce EMT in tumor cells. EMT tumor cells change their adverse microenvironment into a tumor friendly neighborhood, loaded with stromal regulatory T cells, exhausted CD8⁺ T cells, and M2 (protumor) macrophages. Several EMT inhibitory mechanisms are instrumental in reversing EMT or targeting EMT cells. Currently, these mechanisms are also significant for clinical use.

Anti-Tumor Effects of Osthole on Different Malignant Tissues: A Review of Molecular Mechanisms

Cancer management and/or treatment require a comprehensive understanding of the molecular and signaling pathways involved. Recently, much attention has been directed to these molecular and signaling pathways, and it has been suggested that a number of biomolecules/players involved in such pathways, such as PI3K/Akt, NF-kB, STAT, and Nrf2 contribute to the progression, invasion, proliferation, and metastasis of malignant cells. Synthetic anti-tumor agents and chemotherapeutic drugs have been a mainstay in cancer therapy and are widely used to suppress the progression and, hopefully, halt the proliferation of malignant cells. However, these agents have some undesirable side-effects and, therefore, naturally-occurring compounds with high potency and fewer side-effects are now of great interest. Osthole is a plant-derived chemical compound that can inhibit the proliferation of malignant cells and provide potent anti-cancer effects in various tissues. Therefore, in this review, we presented the main findings concerning the potential anti-tumor effects of osthole and its derivatives and described possible molecular mechanisms by which osthole may suppress malignant cell proliferation in different tissues.

Flavonoids sensitize tumor cells to radiation: molecular mechanisms and relevance to cancer radiotherapy

Purpose: Radiobiological research continues to focus on finding newer strategies for enhanced killing of tumor cells by ionizing radiation. In recent years, chemotherapeutic drugs have been found to possess the capabilities to sensitize tumor cells without affecting the normal cells. There have been increasing research efforts to identify novel and nontoxic compounds which cause minimal or no harm to normal cells but maximize tumor toxicity response to radiation exposure. Extensive researches on flavonoids that are compounds derived from plants have shown that these have promising abilities as radioprotectors and radiosensitizers.Conclusions: In this review, we examine the role of flavonoids as potential radiosensitizers, review the underlying molecular mechanisms and discuss their potential usefulness in improving cancer radiotherapy. It is emphasized that obtaining a deeper insight into the molecular mechanisms underlying the combined action of flavonoids and ionizing radiation may provide new directions for radiobiological research applicable to the much needed enhanced selective tumor cytotoxicity to treatment agents.

Usnic acid induces apoptosis in human gastric cancer cells through ROS generation and DNA damage and causes up-regulation of DNA-PKcs and γ-H2A.X phosphorylation

Usnic acid, a dibenzofuran derivative found in many lichen species, is reported to have anticancer activity against human gastric cancer. We investigated the molecular alterations associated with anticancer effects of usnic acid against human gastric adenocarcinoma AGS and gastric carcinoma SNU-1 cells. Usnic acid (10-25 μM) treatment to these cells caused a significant increase in mitochondrial membrane depolarization and apoptotic cells. Apoptosis induction was accompanied by an increase in the ratio of Bax:Bcl-2 expression and cleaved-PARP. Usnic acid increased the comet tail length and tail DNA in alkaline comet assay indicating DNA double-strand breaks which was also evidenced by an increase in γH2A.X (Ser139) phosphorylation. The expression of DNA damage response proteins including DNA-PKcs, pATM (Ser1981), Chk-2 and p53 were increased. Further, N-acetyl cysteine, a known reactive oxygen species (ROS) scavenger, reversed the effects of usnic acid on expression of DNA damage response proteins and γH2A.X (Ser139) phosphorylation. This reversal was also observed in comet assay in a time and dose-dependent manner suggesting that usnic acid-induced DNA damage was caused by ROS. In addition, the non-toxic concentrations (1-10 μM) of usnic acid inhibited colony forming potential of AGS cells indicating its anti-proliferation activity. More importantly, the concentration of usnic acid that caused significant death in gastric cancer cells, did not show any considerable toxicity to normal human embryonic kidney HEK293 cells, human keratinocyte HaCaT cells and mouse primary gastric cells. Collectively, these results for the first time demonstrated the selective apoptotic effect of usnic acid (10-25 μM) through ROS generation and DNA damage on human gastric cancer cells accompanied with upregulation of γH2A.X (Ser139) phosphorylation, DNA-PKcs and p53.

Sulfonyl chromen-4-ones (CHW09) shows an additive effect to inhibit cell growth of X-ray irradiated oral cancer cells, involving apoptosis and ROS generation

Purpose: This study evaluates the growth inhibiting potential of our previously described sulfonyl chromen-4-ones (CHW09) compound in X-ray irradiated oral cancer cells. Materials and methods: The growth inhibiting effect and mechanism of combined CHW09/X-ray treatment was examined by analyzing cell viability, cell cycle, apoptosis, reactive oxygen species (ROS), and DNA damage. Results: Individual treatments of CHW09 (10 μg/mL) and X-ray irradiation (12 Gy) slightly decreased cell viability of oral cancer Ca9-22 (87.25% and 86.54%) and CAL 27 (80.00% and 74.01%) cells and normal oral HGF-1 cells (92.76% and 87.56%) at 24 h-MTS assay, respectively. In a combined treatment (CHW09/X-ray), the cell viability in Ca9-22 and CAL 27 cells was significantly decreased to 73.48% and 59.07%, whereas HGF-1 cells maintained 84.97% viability in 24 h-MTS assay. For CAL 27 cells, both 72 h-MTS assay and clonogenic assay showed that CHW09/X-ray resulted in more growth inhibition than other treatments. Intracellular ROS levels of CHW09/X-ray were higher than for CHW09, X-ray and control. CHW09/X-ray and X-ray alone had higher G2/M arrest than the control and CHW09 alone. Moreover, flow cytometry and western blotting showed that CHW09/X-ray treatment caused higher apoptosis levels. Levels of H2A histone family member X (γH2AX)-based DNA damage and 8-oxo-2'-deoxyguanosine (8-oxodG)-oxidative DNA damage of CHW09/X-ray were higher than for CHW09, X-ray and control. Conclusion: CHW09/X-ray treatment had additive growth inhibiting effects against X-ray irradiated oral cancer cells, partly attributing to apoptosis and ROS generation.

Natural Product Interventions for Chemotherapy and Radiotherapy-Induced Side Effects

Cancer is the second leading cause of death in the world. Chemotherapy and radiotherapy are the common cancer treatments. However, the development of adverse effects resulting from chemotherapy and radiotherapy hinders the clinical use, and negatively reduces the quality of life in cancer patients. Natural products including crude extracts, bioactive components-enriched fractions and pure compounds prepared from herbs as well as herbal formulas have been proved to prevent and treat cancer. Of significant interest, some natural products can reduce chemotherapy and radiotherapy-induced oral mucositis, gastrointestinal toxicity, hepatotoxicity, nephrotoxicity, hematopoietic system injury, cardiotoxicity, and neurotoxicity. This review focuses in detail on the effectiveness of these natural products, and describes the possible mechanisms of the actions in reducing chemotherapy and radiotherapy-induced side effects. Recent advances in the efficacy of natural dietary supplements to counteract these side effects are highlighted. In addition, we draw particular attention to gut microbiotan in the context of prebiotic potential of natural products for the protection against cancer therapy-induced toxicities. We conclude that some natural products are potential therapeutic perspective for the prevention and treatment of chemotherapy and radiotherapy-induced side effects. Further studies are required to validate the efficacy of natural products in cancer patients, and elucidate potential underlying mechanisms.

Osthole enhances antitumor activity and irradiation sensitivity of cervical cancer cells by suppressing ATM/NF‑κB signaling

Osthole (7-methoxy-8-isopentenoxycoumarin) is an O-methylated coumarin, originally extracted from Chinese herbal medicine. It has been demonstrated that osthole has antitumor effects in various cancer cells in vitro. The present study assessed the effects of osthole on the regulation of cervical cancer cell viability, apoptosis, and radiation sensitization. HeLa, SiHa, C-33A and CaSki cervical cancer cell lines were cultured and treated with osthole and/or irradiation and then subjected to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide cell viability, colony formation, apoptosis, acridine orange/ethidium bromide fluorescence staining, wound-healing, Transwell migration and invasion, immunofluorescence, Comet and western blot assays. The data showed that osthole dose-dependently reduced cervical cancer cell viability, proliferation, and migration and invasion, but induced apoptosis. At the protein level, osthole affected the expression of cervical cancer cell epithelial-mesenchymal transition markers, which showed that the expression of E-cadherin was increased, whereas that of vimentin was decreased. Osthole treatment also sensitized cervical cancer cells to irradiation, showing increased DNA damage as assessed by the Comet assay, and inhibited nuclear factor-κB signaling. In conclusion, osthole is an herbal agent that may offer potential for used as an adjuvant treatment for cervical cancer.

Sensitization of prostate cancer to radiation therapy: Molecules and pathways to target

Radiation therapy is used to treat cancer by radiation-induced DNA damage. Despite the best efforts to eliminate cancer, some cancer cells survive irradiation, resulting in cancer progression or recurrence. Alteration in DNA damage repair pathways is common in cancers, resulting in modulation of their response to radiation. This article focuses on the recent findings about molecules and pathways that potentially can be targeted to sensitize prostate cancer cells to ionizing radiation, thereby achieving an improved therapeutic outcome.

Flavonoid silybin improves the response to radiotherapy in invasive bladder cancer

Conservative treatment for invasive bladder cancer (BC) involves a complete transurethral tumor resection combined with chemotherapy (CT) and radiotherapy (RT). The major obstacles of chemo-radiotherapy are the addition of the toxicities of RT and CT, and the recurrence due to RT and CT resistances. The flavonoid Silybin (Sb) inhibits pathways involved in cell survival and resistance mechanisms, therefore the purpose of this paper was to study in vitro and in vivo, the ability of Sb to improve the response to RT, in two murine BC cell lines, with different levels of invasiveness, placing emphasis on radio-sensitivity, and pathways involved in radio-resistance and survival. In vitro, Sb radio-sensitized murine invasive cells through the inhibition of RT-induced NF-κB and PI3K pathways, and the increase of oxidative stress, while non-invasive cells did not show to be sensitized. In vivo, Sb improved RT-response and overall survival in invasive murine tumors. As Sb is already being tested in clinical trials for other urological cancers and it improves RT-response in invasive BC, these results could have translational relevance, supporting further research.

Pituitary-Directed Therapies for Cushing's Disease

Cushing's disease (CD) is caused by a pituitary corticotroph neuroendocrine tumor inducing uncontrolled hypercortisolism. Transsphenoidal surgery is the first-line treatment in most cases. Nonetheless, some patients will not achieve cure even in expert hands, others may not be surgical candidates and a significant percentage will experience recurrence. Many patients will thus require medical therapy to achieve disease control. Pharmacologic options to treat CD have increased in recent years, with an explosion in knowledge related to pathophysiology at the molecular level. In this review, we focus on medications targeting specifically pituitary adrenocorticotropic hormone-secreting tumors. The only medication in this group approved for the treatment of CD is pasireotide, a somatostatin receptor ligand. Cabergoline and temozolomide may also be used in select cases. Previously studied and abandoned medical options are briefly discussed, and emphasis is made on upcoming medications. Mechanism of action and available data on efficacy and safety of cell cycle inhibitor roscovitine, epidermal growth factor receptor inhibitor gefitinib, retinoic acid, and silibinin, a heat shock protein 90 inhibitor are also presented.

Silibinin attenuates radiation-induced intestinal fibrosis and reverses epithelial-to-mesenchymal transition

Radiotherapy is a common treatment for cancer patients, but its use is often restricted by the tolerance of normal tissue. As cancer patients live longer, delayed radiation effects on normal tissue have become a concern. Radiation-induced enteropathy, including inflammatory bowel disease and fibrosis, are major issues for long-term cancer survivors. To investigate whether silibinin attenuates delayed radiation-induced intestinal injury in mice, we focused on intestinal fibrotic changes. Silibinin improved delayed radiation injuries in mice in association with decreased collagen deposition within the intestines and deceased transforming growth factor (TGF)-β1 levels in the intestine and plasma. Treating mice bearing CT26 mouse colon cancer tumors with both silibinin and radiation stimulated tumor regression more than radiation alone. We also investigated the effect of silibinin on the radiation-induced epithelial-to-mesenchymal transition (EMT), the primary mechanism of fibrosis. We assessed changes in E-cadherin, N-cadherin, and α-smooth muscle actin expression, and demonstrated that silibinin attenuates radiation-induced EMT. Irradiating intestinal epithelial cells increased TGF-β1 levels, but silibinin suppressed TGF-β1 expression by inhibiting Smad2/3 phosphorylation. These results suggest silibinin has the potential to serve as a useful therapeutic agent in patients with radiation-induced intestinal fibrosis.

Silibinin stimluates apoptosis by inducing generation of ROS and ER stress in human choriocarcinoma cells

Silibinin is a flavonolignan extracted from seeds of milk thistles. Traditionally, it has been used as a therapeutic agent for liver disorders, and now it is well-known for its anti-cancer effects. However, studies on anti-cancer effects of silibinin on choriocarcinoma are very limited. Therefore, we performed proliferation and apoptosis assays to determine effects of silibinin on the viability of human choriocarcinoma (JAR and JEG3) cells. Our results showed that silibinin significantly inhibited proliferation and induced apoptosis in both JAR and JEG3 cells, and significantly increased reactive oxygen species (ROS) and lipid peroxidation. Moreover, silibinin disrupted mitochondrial function by inducing permeabilization of mitochondrial membrane potential and calcium ion efflux in JAR and JEG3 cells. Furthermore, silibinin-induced apoptosis in choriocarcinoma cells via AKT, mitogen-activated protein kinases (MAPK) and unfolded protein response (UPR) signal transduction. Collectively, our results suggest that silibinin is a novel therapeutic agent or dietary supplement for management of human placental choriocarcinomas.

pATM and γH2AX are effective radiation biomarkers in assessing the radiosensitivity of 12C6+ in human tumor cells

Background

Tumour radiosensitivity would be particularly useful in optimizing the radiation dose during radiotherapy. The aim of the current study was to evaluate the potential value of phosphorylated H2AX (γH2AX) and ATM (pATM) in assessing ¹²C⁶⁺ radiosensitivity of tumour cells.

Methods

Human cervical carcinoma HeLa cells, hepatoma HepG2 cells, and mucoepidermoid carcinoma MEC-1 cells were irradiated with different doses of ¹²C⁶⁺. The survival fraction was assayed with clonogenic survival method and the foci of γH2AX and pATM was visualized using immunocytochemical methods. Flow cytometry was used to assay γH2AX, pATM and the cell cycle.

Results

The survival fraction decreased immediately in dose-dependent manner, but in turn, significantly increased during 24 h after ¹²C⁶⁺ irradiation. Both γH2AX and pATM foci accumulated linearly with doses and with a maximum induction at 0.5 h for γH2AX and 0.5 or 4 h for pATM, respectively, and a fraction foci kept for 24 h. The expression of γH2AX and pATM was in relation to cell cycle. The G0/G1 phase cells had the highest expression of γH2AX after 0.5 h irradiation and then decreased to a lower level at 24 h after irradiation. An obvious increase of pATM in G2/M phase was shown after 24 h of 2 and 4 Gy irradiation. The significant G2/M phase arrest was shown. There was a close relationship between the clonogenic survival and γH2AX and pATM expression both in timing and dose in response to ¹²C⁶⁺.

Conclusions

The rate of γH2AX and pATM formation and loss may be an important factor in the response of cells to ¹²C⁶⁺. pATM and γH2AX are effective radiation biomarkers in assessing the radiosensitivity of ¹²C⁶⁺ in human tumor cells.

Silibinin protects Staphylococcus aureus from UVC-induced bactericide via enhanced generation of reactive oxygen species

ROS produced by silibinin suppresses UVC-inducedStaphylococcus aureuscell death.

Herbal Medicine Offered as an Initiative Therapeutic Option for the Management of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common malignant cancer and is the third leading cause of death worldwide. Effective treatment of this disease is limited by the complicated molecular mechanism underlying HCC pathogenesis. Thus, therapeutic options for HCC management are urgently needed. Targeting the Wnt/β-catenin, Hedgehog, Notch, and Hippo-YAP signaling pathways in cancer stem cell development has been extensively investigated as an alternative treatment. Herbal medicine has emerged as an initiative therapeutic option for HCC management because of its multi-level, multi-target, and coordinated intervention effects. In this article, we summarized the recent progress and clinical benefits of targeting the above mentioned signaling pathways and using natural products such as herbal medicine formulas to treat HCC. Proving the clinical success of herbal medicine is expected to deepen the knowledge on herbal medicine efficiency and hasten the adoption of new therapies. Copyright © 2016 John Wiley & Sons, Ltd.