Astaxanthin increases radiosensitivity in esophageal squamous cell carcinoma through inducing apoptosis and G2/M arrest

Astaxanthin Synergizes with Ionizing Radiation (IR) in Oral Squamous Cell Carcinoma (OSCC)

Astaxanthin (ATX) is known for its antioxidant and anti-inflammation functions yet its role in cancers requires more research. This study is aimed to reveal the potential synergetic effect of ATX with ionizing radiation (IR) in OSCC. Cell survival was measured after human OSCC cells including CAL27 and SCC9, and normal human oral keratinocytes (NHOKs) were treated with different concentrations of ATX for 24 h. Colony formation assays were performed after OSCC cells were treated with IR, ATX (20 μ M), or combined and survival fraction was analyzed. Malondialdehyde (MDA), glutathione (GSH), and intercellular iron levels were measured. Western blot method was used to measure the ferroptosis-related proteins, GPX4, SLC7A11, and ACSL4. In xenograft mice model, we evaluated the tumor volumes, tumor growth, and examined the GPX4/ACSL4 proteins in tumor tissues using Immunohistochemistry (IHC). ATX inhibited viability of OSCC cells but not NHOK. In OSCC cells, ATX further enhanced the cell death induced by IR. In addition, ATX promoted the MDA content, Iron levels but inhibited the GSH regulated by IR in cells. ATX could synergize with IR, further inhibiting GPX4, SLC7A11 and promoting ACSL4 in OSCC cells. In vivo, ATX and IR treatment inhibited OSCC tumor growth and the group with combined treatment showed the most inhibitory effect. GPX4 was inhibited by IR and further inhibited in the combined group while ACSL4 was promoted by IR and enhanced more significantly in the combined group. ATX might synergize with IR treatment in OSCC partly via ferroptosis.

Curcumol β-cyclodextrin inclusion complex enhances radiosensitivity of esophageal cancer under hypoxic and normoxic condition

PURPOSE

Radiotherapy is an indispensable treatment for esophageal cancer (EC), but radioresistance is not uncommon. Curcumol, as an active extract from traditional Chinese medicines, has been reported to have antitumor activity in various types of human tumor cells. However, its reversal of radioresistance has been rarely reported.

MATERIALS AND METHODS

In the present study, curcumol was prepared as an inclusion complex with β-cyclodextrin. EC cell lines were treated with radiation and curcumol β-cyclodextrin inclusion complex (CβC), and the effect of radiosensitization of CβC was investigated in vitro and in vivo. The in vitro experiments included cell proliferation assay, clonogenic survival assay, apoptosis assay, cell cycle assay, and western blot assay.

RESULTS

The in vitro data revealed that CβC and irradiation synergistically inhibited the proliferation, reduced the colony formation, promoted the apoptosis, increased the G2/M phase, inhibited DNA damage repair, and reversed the hypoxia-mediated radioresistance of EC cells to a greater extent than did CβC alone or irradiation alone. The sensitization enhancement ratios (SERs) were 1.39 for TE-1 and 1.48 for ECA109 under hypoxia. The SERs were 1.25 for TE-1 and 1.32 for ECA109 under normoxia. The in vivo data demonstrated that the combination of CβC and irradiation could inhibit tumor growth to the greatest extent compared with either monotherapy alone. The enhancement factor was 2.45.

CONCLUSION

This study demonstrated that CβC could enhance radiosensitivity of EC cells under hypoxic and normoxic condition. Thus, CβC can be used as an effective radiosensitizer for EC.

ERK inhibitor: A candidate enhancing therapeutic effects of conventional chemo-radiotherapy in esophageal squamous cell carcinoma

For patients with esophageal squamous cell carcinoma (ESCC), standard therapeutic methods (cisplatin and radiotherapy) have been found to be ineffective and severely toxic. Targeted therapy emerges as a promising solution for this dilemma. It has been reported that targeted therapies are applied alone or in combination with standard conventional therapies for the treatment of a variety of cancers. To the best of our knowledge, in patients with ESCC, the combinational methods containing standard therapy and ERK-targeted therapy have yet to be explored. To analyze the prognostic role of p-ERK in ESCC patients, the Kaplan-Meier analysis and Cox regression model were used. To assess the effects of ERK-targeted therapy (GDC0994) on ESCC cells, in vitro studies including CCK-8 assay, colony formation assay, and scratch wound healing assay were conducted. In addition, the changes in cell cycle distribution and apoptosis were analyzed by flow cytometry. Besides, to assess the efficacy of different therapies in vivo, the xenograft tumor models were established by subcutaneously inoculating tumor cells into the flank/leg of mice. In patients with ESCC, a strong correlation between the high expression level of p-ERK and the poor prognosis (p < 0.01, Log-Rank test) has been identified. By analyzing the results from CCK-8 and scratch wound healing assays, we demonstrated that the ERK inhibitor repressed the viability and migration of ESCC cells. In addition, following the treatment of GDC0994, the volumes of xenograft tumors significantly decreased (p < 0.001, one-way ANOVA). Furthermore, blocking the mitogen-activated protein kinase (MAPK/ERK) pathway enhanced the therapeutic efficacy of both cisplatin and radiotherapy (p < 0.05). These findings imply the role of p-ERK in the prognosis of ESCC patients and the therapeutic value of ERK inhibitors in ESCC.

miR-302a-3p Promotes Radiotherapy Sensitivity of Hepatocellular Carcinoma by Regulating Cell Cycle via MCL1

Background. The relationship between tumor suppressor gene miR-302a-3p and radiotherapy for hepatocellular carcinoma (HCC) remains unclear. This study intended to illustrate the molecular mechanism how miR-302a-3p regulated radiotherapy sensitivity of HCC. Methods. miR-302a-3p expression in HCC tissues and cells was examined by qRT-PCR. The effect of miR-302a-3p on HCC radiotherapy sensitivity were detected by CCK-8, colony formation, and flow cytometry assays. The expression levels of cell cycle-related proteins were detected by Western blot. The influence of miR-302a-3p on radiotherapy sensitivity of HCC was further investigated via cell cycle inhibitor (Caudatin) treatment. The target gene (MCL1) of miR-302a-3p was obtained by bioinformatics analysis, and their binding relationship was confirmed by RNA-binding protein immunoprecipitation assay. The mechanisms of miR-302a-3p regulating cell cycle and affecting radiotherapy sensitivity of HCC cells through MCL1 were further explored through the rescue experiments. Results. miR-302a-3p expression was remarkably reduced in radiotherapy-resistant tissues and cells of HCC. miR-302a-3p overexpression restored sensitivity of radiotherapy-resistant HCC cells to radiotherapy. Treatment with cell cycle inhibitor Caudatin could reverse suppressive effect of miR-302a-3p downregulation on sensitivity of HCC to radiotherapy. Additionally, miR-302a-3p could restrain MCL1 expression. In vitro cell assays further revealed that miR-302a-3p/MCL1 axis could enhance radiotherapy sensitivity of HCC cells by inducing G0/G1 arrest. Conclusions. miR-302a-3p facilitated radiotherapy sensitivity of HCC cells by regulating cell cycle via MCL1, which provided a new underlying target for radiotherapy resistance of HCC patients.

Replication Stress: A Review of Novel Targets to Enhance Radiosensitivity-From Bench to Clinic

DNA replication is a process fundamental in all living organisms in which deregulation, known as replication stress, often leads to genomic instability, a hallmark of cancer. Most malignant tumors sustain persistent proliferation and tolerate replication stress via increasing reliance to the replication stress response. So whilst replication stress induces genomic instability and tumorigenesis, the replication stress response exhibits a unique cancer-specific vulnerability that can be targeted to induce catastrophic cell proliferation. Radiation therapy, most used in cancer treatment, induces a plethora of DNA lesions that affect DNA integrity and, in-turn, DNA replication. Owing to radiation dose limitations for specific organs and tumor tissue resistance, the therapeutic window is narrow. Thus, a means to eliminate or reduce tumor radioresistance is urgently needed. Current research trends have highlighted the potential of combining replication stress regulators with radiation therapy to capitalize on the high replication stress of tumors. Here, we review the current body of evidence regarding the role of replication stress in tumor progression and discuss potential means of enhancing tumor radiosensitivity by targeting the replication stress response. We offer new insights into the possibility of combining radiation therapy with replication stress drugs for clinical use.

Targeting RAS–RAF–MEK–ERK signaling pathway in human cancer: Current status in clinical trials

Molecular target inhibitors have been regularly approved by Food and Drug Administration (FDA) for tumor treatment, and most of them intervene in tumor cell proliferation and metabolism. The RAS-RAF-MEK-ERK pathway is a conserved signaling pathway that plays vital roles in cell proliferation, survival, and differentiation. The aberrant activation of the RAS-RAF-MEK-ERK signaling pathway induces tumors. About 33% of tumors harbor RAS mutations, while 8% of tumors are driven by RAF mutations. Great efforts have been dedicated to targeting the signaling pathway for cancer treatment in the past decades. In this review, we summarized the development of inhibitors targeting the RAS-RAF-MEK-ERK pathway with an emphasis on those used in clinical treatment. Moreover, we discussed the potential combinations of inhibitors that target the RAS-RAF-MEK-ERK signaling pathway and other signaling pathways. The inhibitors targeting the RAS-RAF-MEK-ERK pathway have essentially modified the therapeutic strategy against various cancers and deserve more attention in the current cancer research and treatment.

Fruit and vegetable consumption and risk of esophageal cancer in the Asian region: a systematic review and meta-analysis

The consumption of fruit and vegetables was reported to be associated with a reduced risk of esophageal cancer (EC) in many studies of esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC) from different regions worldwide. Therefore, to provide precise information to reduce the risk of EC in Asia, we performed a systematic review and meta-analysis of studies conducted in the Asian region about fruit and vegetable consumption and the risk of EC. We searched the MEDLINE (PubMed) and ICHUSHI (Japana Centra Revuo Medicina) databases from January 2010 to December 2020. The summary relative risk (SRR) and 95% CI were calculated using a random-effects model. In addition, I² statistics were used to detect heterogeneity. Twenty-two studies were eligible for meta-analysis (16 case-control studies and 6 cohort studies). The SRR for the lowest versus highest fruit consumption was 0.64 (95% CI 0.53-0.77, I² = 82%). That for the lowest versus highest vegetable consumption was 0.61 (95% CI 0.50-0.74, I² = 81%). Based on subgroup analysis, a validated Food Frequency Questionnaire (FFQ) was significantly associated (SRR for fruit: 0.54; 95% CI 0.40-0.74, SRR for vegetable: 0.60; 95% CI 0.48-0.76) with low heterogeneity (I² = 48% for fruit, I² = 0% for vegetables). Egger's funnel plot asymmetry test demonstrated publication bias (P < 0.001 for fruit, P = 0.009 for vegetables). Fruit and vegetable consumption might be associated with a lower risk of EC in the Asian region. However, further substantial prospective studies with a validated FFQ and well-controlled important confounding factors are required to confirm the association.

Radiation induces NORAD expression to promote ESCC radiotherapy resistance via EEPD1/ATR/Chk1 signalling and by inhibiting pri-miR-199a1 processing and the exosomal transfer of miR-199a-5p

BACKGROUND

Radioresistance, a poorly understood phenomenon, results in the failure of radiotherapy and subsequent local recurrence, threatening a large proportion of patients with ESCC. To date, lncRNAs have been reported to be involved in diverse biological processes, including radioresistance.

METHODS

FISH and qRT-PCR were adopted to examine the expression and localization of lncRNA-NORAD, pri-miR-199a1 and miR-199a-5p. Electron microscopy and nanoparticle tracking analysis (NTA) were conducted to observe and identify exosomes. High-throughput microRNAs sequencing and TMT mass spectrometry were performed to identify the functional miRNA and proteins. A series of in vitro and in vivo experiments were performed to investigate the biological effect of NORAD. ChIP, RIP-qPCR, co-IP and dual-luciferase reporter assays were conducted to explore the interaction of related RNAs and proteins.

RESULTS

We show here that DNA damage activates the noncoding RNA NORAD, which is critical for ESCC radioresistance. NORAD was expressed at high levels in radioresistant ESCC cells. Radiation treatment promotes NORAD expression by enhancing H3K4me2 enrichment in its sequence. NORAD knockdown cells exhibit significant hypersensitivity to radiation in vivo and in vitro. NORAD is required to initiate the repair and restart of stalled forks, G2 cycle arrest and homologous recombination repair upon radiation treatment. Mechanistically, NORAD inhibits miR-199a-5p expression by competitively binding PUM1 from pri-miR-199a1, inhibiting the processing of pri-miR-199a1. Mature miR-199a-5p in NORAD knockdown cells is packaged into exosomes; miR-199a-5p restores the radiosensitivity of radioresistant cells by targeting EEPD1 and then inhibiting the ATR/Chk1 signalling pathway. Simultaneously, NORAD knockdown inhibits the ubiquitination of PD-L1, leading to a better response to radiation and anti-PD-1 treatment in a mouse model.

CONCLUSIONS

Based on the findings of this study, lncRNA-NORAD represents a potential treatment target for improving the efficiency of immunotherapy in combination with radiation in ESCC.

Antitumor Effects of Astaxanthin on Esophageal Squamous Cell Carcinoma by up-Regulation of PPARγ

Esophageal squamous cell carcinoma is a malignant tumor that is difficult to find and has a poor prognosis. The aim of this study is to explore the chemoprevention effect of Astaxanthin (AST) and reveal the possible mechanism of AST on the development of esophageal cancer based on PPARγ. We found that a stable and strong binding between PPARγ molecules and AST molecules using Autodock 4.0 software. AST significantly inhibited the viability of EC109 cells in a dose and time dependent manners (all P < 0.05), and up-regulated the protein expression level of PPARγ from the concentration of 6.25 µM (P < 0.05). Animal experiment showed that AST significantly decreased the incidences of NMBzA-induced esophageal carcinogenesis at 50 mg/kg AST in F344 rats (P < 0.05). AST inhibited the oxidative stress by improving the levels of superoxide dismutase (SOD), total antioxidant capacity (TAOC) and suppressing malondialdehyde (MDA) in serum, and increasing the protein of PPARγ, Bax/Bcl-2, Caspase-3 in esophagus tissue, especially in the 50 mg/kg of AST intervention group (all P < 0.05). In conclusion, our data suggested that protective effect of AST on esophageal cancer by inhibiting oxidative stress, up-regulating PPARγ, and activating the apoptotic pathway, which could provide a basis for clinical application of AST.

Synergic radiosensitization of sinomenine hydrochloride and radioiodine on human papillary thyroid carcinoma cells

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This is the first time to study and find out that sinomenine hydrochloride and iodine-131 synergic enhance the apoptosis and regulate DNA repair and cell cycle checkpoint on papillary thyroid carcinoma cells.

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This is the first time to study and find out that sinomenine hydrochloride increased the radiosensitivity of papillary thyroid carcinoma cells and normal thyroid cells.

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This is the first time to study and find out that sinomenine hydrochloride could be a potential therapeutic radiosensitizer in papillary thyroid carcinoma radiotherapy after total thyroidectomy .

Radioiodine (¹³¹I) therapy is an important treatment for thyroid carcinoma. The response to radiotherapy sometimes limited by the development of radioresistance. Sinomenine hydrochloride(SH), was reported as a prospective radiosensitizer. This study was aim to evaluate synergic radiosensitization of SH and ¹³¹I on papillary thyroid carcinoma (PTC). We evaluated HTori-3, BCPAP and TPC-1 cells, the cell viability was evaluated by MTT. The experiment was divided into 4 groups: control group, SH (0.8 mM) group, I (¹³¹I 14.8 MBq/ml) group and ISH (SH 0.8 mM plus ¹³¹I 14.8 MBq/ml) group. Flow cytometry was used to investigate cell cycle phases and cell apoptosis. RT-PCR and western blotting were performed to determine the molecular changes. Compared to control group, SH significantly increased apoptosis and enhanced radiosensitivity of HTori-3 and PTC cells were related to the ratio of Bcl-2 to Bax protein downregulation and Fas, p21, p-ATM, p-Chk1, p-Chk2 and p53 protein expression upregulation in the ISH group (P < 0.05). Our results indicate that synergic radiosensitization of SH and iodine-131 on PTC cells and SH could be a potential therapeutic radiosensitizer in PTC radio therapy after total thyroidectomy.

Knockdown of Ubiquitin-Specific Protease 53 Enhances the Radiosensitivity of Human Cervical Squamous Cell Carcinoma by Regulating DNA Damage-Binding Protein 2

Background:

Cervical cancer ranks fourth in incidence and mortality among women. Ubiquitin-specific protein 53 binds to damage-specific DNA binding protein 2 and affects the biological properties of colon cancer. Damage-specific DNA binding protein is involved in nucleotide excision repair, which can repair DNA damage. However, the mechanism by which ubiquitin-specific protein 53 regulates the radiosensitivity of cervical cancer through damage-specific DNA binding protein remains unclear.

Methods:

Tissue samples from 40 patients with cervical squamous cell carcinoma who received radiotherapy were examined by immunohistochemistry to detect the expression of ubiquitin-specific protein 53, and clinical data were collected for statistical analysis. The cell cycle was detected by flow cytometry in Siha cells transfected with Si-USP53 and exposed to 8 Gy irradiation. Cell viability was determined by the CCK8 method in cells transfected with Si-USP53 and exposed to 0, 2, 4, 6, 8, or 10 Gy. The expression of damage-specific DNA binding protein, cyclin-dependent kinase 1, and cell cycle checkpoint kinase 2 was detected in cells transfected with Si-USP53.

Results:

The expression of ubiquitin-specific protein 53 in the tissues of patients with cervical squamous cell carcinoma was correlated with the sensitivity to radiotherapy. Knockdown of ubiquitin-specific protein 53 in Siha cells downregulated damage-specific DNA binding protein and caused G2/M cell cycle arrest and decreased the survival rate of cells in response to radiation.

Conclusion:

Ubiquitin-specific protein 53–induced cell cycle arrest and affected the radiotherapy sensitivity of tumors through damage-specific DNA binding protein.

Zeaxanthin Induces Apoptosis via ROS-Regulated MAPK and AKT Signaling Pathway in Human Gastric Cancer Cells

BACKGROUND

Zeaxanthin, a carotenoid commonly found in plants, has a variety of biological functions including anti-cancer activity.

PURPOSE

This study aimed to investigate the potential mechanisms of zeaxanthin in human gastric cancer cells.

METHODS

CCK-8 assay was used to examine the cytotoxic effect of zeaxanthin on human gastric cancer cells. Flow cytometry was used to analyse AGS cell cycle distribution and apoptosis status. Western blot analysis was used to detect the expression levels of cycle-related proteins (Cyclin A, Cyclin B1, CDK1/2, p21, and p27), apoptosis-related proteins (Bcl-2, Bad, caspase-3, PARP), MAPK, AKT, STAT3, and NF-κB.

RESULTS

CCK-8 assay showed that zeaxanthin has obvious cytotoxic effects on 12 types of human gastric cancer cells, but no obvious toxic effect on normal cells. In addition, flow cytometry and Western blotting results showed that zeaxanthin induces apoptosis by reducing mitochondrial membrane potential; increasing Cytochrome C, Bax, cleaved-caspase-3 (cle-cas-3), and cleaved-PARP (cle-PARP) expression levels; and decreasing Bcl-2, pro-caspase-3 (pro-cas-3), and pro-PARP expression levels. Additionally, zeaxanthin caused cell cycle arrest at the G2/M phase by increasing the levels of p21 and p27 and reduced the levels of AKT, Cyclin A, Cyclin B1, and Cyclin-dependent kinase 1/2 (CDK1/2). Furthermore, after zeaxanthin treatment, the expression levels of reactive oxygen species (ROS), p-JNK, p-p38, and I-κB increased, and the expression levels of p-ERK, p-AKT, STAT3, and NF-κB decreased. However, the ROS scavenger N-acetylcysteine (NAC) and MAPK inhibitors inhibited zeaxanthin-induced apoptosis, and under the action of zeaxanthin, MAPK regulated NF-κB and STAT3, and reduced their protein expression levels.

CONCLUSION

Zeaxanthin has a potential effect against gastric cancer cells through the ROS-mediated MAPK, AKT, NF-κB, and STAT3 signaling pathways, and it is expected to become a new drug for the treatment of human gastric cancer.

Decreased plasma riboflavin is associated with poor prognosis, invasion, and metastasis in esophageal squamous cell carcinoma

BACKGROUND

Riboflavin deficiency confers a predisposition for esophageal cancer. The role of plasma riboflavin levels in development and prognosis of individuals with digestive tract inflammation and ulcer (DTIU), digestive tract polyps (DTPs), and ESCC is not well understood.

METHODS

We performed a cross-sectional study, including 177 DTIU, 80 DTP, and 324 ESCC cases, to measure the plasma riboflavin levels among the three populations. Correlation between plasma riboflavin levels (categorized as ≥31.8, 6.5-31.8 and ≤6.5 nmol/L groups) and clinical characteristics, as well as survival of ESCC patients (556 cases) was analyzed.

RESULTS

There was no difference in plasma riboflavin levels between DTIU, DTP, and ESCC cases (P > 0.05). Plasma riboflavin levels were inversely correlated with invasive depth (correlation coefficient = -0.09, P = 0.026) and lymph node metastasis (correlation coefficient = -0.11, P = 0.010) of ESCC, and ESCC patients with low riboflavin levels had poor recurrence-free survival (P = 0.035) and overall survival (P = 0.003). Decreased riboflavin was a prognostic factor for poor overall survival (HR = 1.91, 95% CI = 1.19-3.07, P = 0.007).

CONCLUSIONS

Plasma riboflavin levels in DTIU, DTP, and ESCC patients are similar. Plasma riboflavin levels are associated with the development and prognosis of ESCC.

Astaxanthin anticancer effects are mediated through multiple molecular mechanisms: A systematic review

During the latest decades, the interest on the effectiveness of natural compounds and their impact on human health constantly increased, especially on those demonstrating to be effective on cancer. Molecules coming from nature are currently used in chemotherapy like Taxol, Vincristine or Vinblastine, and several other natural substances have been showed to be active in reducing cancer cell progression and migration. Among them, astaxanthin, a xanthophyll red colored carotenoid, displayed different biological activities including, antinflammatory, antioxidant, proapoptotic, and anticancer effects. It can induce apoptosis through downregulation of antiapoptotic protein (Bcl-2, p-Bad, and survivin) expression and upregulation of proapoptotic ones (Bax/Bad and PARP). Thanks to these mechanisms, it can exert anticancer effects towards colorectal cancer, melanoma, or gastric carcinoma cell lines. Moreover, it possesses antiproliferative activity in many experimental models and enhances the effectiveness of conventional chemotherapic drugs on tumor cells underling its potential future use. This review provides an overview of the current knowledge on the anticancer potential of astaxanthin by modulating several molecular targets. While it has been clearly demonstrated its multitarget activity in the prevention and regression of malignant cells in in vitro or in preclinical investigations, further clinical studies are needed to assess its real potential as anticancer in humans.

Elevation of long non-coding RNA GAS5 and knockdown of microRNA-21 up-regulate RECK expression to enhance esophageal squamous cell carcinoma cell radio-sensitivity after radiotherapy

OBJECTIVE

Lately, lncRNAs have been proposed to function in the radio-sensitivity of tumor cells, yet the role of lncRNA GAS5 in that of esophageal squamous cell carcinoma (ESCC) has scarcely been studied. This study aims to examine GAS5's effects on ESCC cell radio-sensitivity.

METHODS

GAS5, miR-21 and RECK expression in radiation-sensitive and radiation-resistant ESCC tissues, and TE-1 and TE-1-R cells was determined. TE-1 and TE-1-R cells were treated with pcDNA-GAS5 or miR-21 inhibitors to figure out their roles in ESCC cell proliferation, radio-sensitivity, and apoptosis via gain- and loss-of-function experiments.

RESULTS

We found underexpressed GAS5 and RECK, and overexpressed miR-21 in ESCC. GAS5 elevation and miR-21 inhibition reduced viability and the colony formation ability, and enhanced the apoptosis of ESCC cells under radiation.

CONCLUSION

Our study reveals that GAS5 elevation up-regulates RECK expression by down-regulating miR-21 to increase ESCC cell apoptosis after radiation therapy, thus enhancing cell radio-sensitivity.

Natural products: An upcoming therapeutic approach to cancer

Cancer is one of the leading causes of death across the world. Different environmental and anthropogenic factors initiate mutations in different functional genes of growth factors and their receptors, anti-apoptotic proteins, self-renewal developmental proteins, tumor suppressors, transcription factors, etc. This phenomenon leads to altered protein homeostasis of the cell which in turn induces cancer initiation, development, progression and survival. From ancient times various natural products have been used as traditional medicine against different diseases. Natural products are readily applicable, inexpensive, accessible and acceptable therapeutic approach with minimum cytotoxicity. As most of the target-specific anticancer drugs failed to achieve the expected result so far, new multi-targeted therapies using natural products have become significant. In this review, we have summarized the efficacy of different natural compounds against cancer. They are capable of modulating cancer microenvironment and diverse cell signaling cascades; thus playing a major role in combating cancer. These compounds are found to be effective against several signaling pathways, mainly cell death pathways (apoptosis and autophagy) and embryonic developmental pathways (Notch pathway, Wnt pathway and Hedgehog pathway). This review article is expected to be helpful in understanding the recent progress of natural product research for the development of anticancer drug.

Reprogramming factors induce proliferation and inhibit apoptosis of melanoma cells by changing the expression of particular genes

Uncontrolled proliferation and defective apoptosis are two major factors responsible for maintaining the malignant properties of melanoma cells. Our previous study demonstrated that induced expression of four reprogramming factors remodeled the phenotype of B16‑F10 mouse melanoma cells into melanoma stem cells. The present study was conducted to investigate the effect of the four Yamanaka reprogramming factors, namely Oct4, Sox2, Klf4 and c‑Myc (OSKM), on the proliferation and apoptosis of melanoma cells, and to identify the responsible molecular signals. The results identified that expression of the four reprogramming factors was highly induced by doxycycline treatment in the stable melanoma cell clone that was transfected with a plasmid expressing these factors, driven by the Tet‑On element. It was further confirmed that induced expression of these factors enhanced the proliferation and suppressed the apoptosis of the melanoma cells. In addition, induced OSKM expression increased cell proliferation, accelerated the progression of the cell cycle, and upregulated the mRNA expression levels of Janus kinase 2 (JAK2) and Cyclin‑B1. Induced expression of these factors also decreased the apoptosis, as well as upregulated B‑cell lymphoma 2 (BCL‑2) and downregulated BCL‑2‑associated X (BAX) mRNA expression levels. Taken together, the results suggested that upregulated JAK2 and Cyclin‑B1 may be responsible for the enhanced proliferation of melanoma cells, and that BCL‑2 upregulation and BAX downregulation may account for the suppressed apoptosis of these cells.

Modified Citrus Pectin as a Potential Sensitizer for Radiotherapy in Prostate Cancer

Background: Radiotherapy is one of the primary therapies for localized prostatic carcinoma. Therefore, there is an emerging need to sensitize prostatic cancer cells to chemotherapy/radiotherapy. Modified citrus pectin (MCP) is an effective inhibitor of galectin-3 (Gal-3), which is correlated with tumor progression, proliferation, angiogenesis, and apoptosis. Purpose: This study was directed to evaluate the efficacy of combining ionizing radiation (IR) with MCP on PCa cells. Study Design: Effects of treatments on PCa cells survival were evaluated using XTT assay, flow cytometry, and clonogenic survival assay. Expression of selected proteins was estimated using western blotting. Cell motility, migration, and invasion were determined. Contribution of reactive oxygen species production to treatment effects on cell viability was tested. Results: Radiotherapy combined with MCP reduced viability and enhanced radiosensitivity associated with a decrease in Gal-3, cleavage of the precursor of caspase-3, increased expression of the pro-apoptotic protein Bax, and downregulation of DNA repair pathways, poly-ADP-ribose polymerase, and proliferating cell nuclear antigen. MCP significantly reduced the invasive and migratory potential of PCa cells. Combining sodium pyruvate with MCP and IR mitigated the effect on cell viability. Conclusion: Our findings demonstrated that MCP sensitized PCa cells to IR by downregulating anti-apoptotic Gal-3, modulating DNA repair pathways, and increasing ROS production. For the first time the correlation between MCP, radiotherapy, and Gal-3 for prostatic cancer treatment was found. In addition, MCP reduced the metastatic properties of PCa cells. These findings provide MCP as a radiosensitizing agent to enhance IR cytotoxicity, overcome radioresistance, and reduce clinical IR dose.

Influence of POLG on Radiosensitivity of Nasopharyngeal Carcinoma Cells

BACKGROUND AND OBJECTIVE

There is a high incidence of nasopharyngeal carcinoma (NPC), malignant head and neck tumors, in southern China. Radioresistance is the main cause affecting the efficacy of NPC treatments. The POLG gene particularly plays an important role in radiation-induced damage repair. In this study, the authors established RNAi CNE-1 and CNE-2 knockdown in two NPC cell lines to observe whether this gene affects the radiosensitivity of NPC cells.

MATERIALS AND METHODS

Four short hairpin RNA (shRNA) expression plasmids targeting POLG gene were constructed and transfected into the NPC cell lines CNE-1 and CNE-2. Screening was performed to evaluate the stable expression of cloned cells, which were named CNE-1/POLG-shRNA1, CNE-1/POLG-shRNA2, CNE-2/POLG-shRNA1, and CNE-2/POLG-shRNA2. The negative controls CNE-1/Neg-shRNA and CNE-2/Neg-shRNA were additionally used. The MTT method, flow cytometry, clone formation analysis, cell migration, and other experimental methods were employed to verify changes in the radiosensitivity of the NPC cells.

RESULTS

Fluorescent quantitative PCR and Western blot confirmed the downregulation of the PLOG gene through diminished PLOG messenger RNA and protein levels. Consequently, the authors report the stable knockdown of the POLG gene in an NPC model. Dose-dependent radiation exposure of POLG inhibited NPC cell growth and increased apoptosis compared with control cells (p < 0.01), as demonstrated through colony formation assay and flow cytometry. Functional assays indicated that knockdown of the POLG in CNE-1 and CNE-2 cells remarkably reduced cell viability and proliferation. Specifically, POLG knockdown led to G1 phase arrest and apoptosis.

CONCLUSIONS

Overall, the authors conclude that POLG downregulation alters the radiosensitivity of NPC cells, indicating that the gene is likely involved in conferring the radiation response of the cells. In addition, findings in this study suggest a novel role for POLG as a potential predictive marker for NPC radiotherapy efficiency. POLG gene can be used as a potential clinical target to effectively improve the radiosensitivity of NPC.

Effect of sinomenine hydrochloride on radiosensitivity of esophageal squamous cell carcinoma cells

Radiation therapy is one of the most important treatments for unresectable and locally advanced esophageal squamous cell carcinoma (ESCC), however, the response to radiotherapy is sometimes limited by the development of radioresistance. Sinomenine hydrochloride (SH) has anticancer activity, but its effect on the radiosensitivity of ESCC is unclear. We determined the effect of SH on the radiosensitivity of ESCC cells and elucidated its potential radiosensitization mechanisms in vitro and in vivo. ESCC cells were subjected to SH and radiation, both separately and in combination. Untreated cells served as controls. The CCK-8 assay was used to evaluate cell proliferation, and the clonogenic assay to estimate radiosensitization. Flow cytometry was used to investigate cell cycle phases and cell apoptosis. Bcl-2, Bax, cyclin B1, CDK1, Ku86, Ku70, and Rad51 expression was evaluated using western blotting. In vivo, tumor xenografts were created using BALB/c nude mice. Tumor-growth inhibition was recorded, and Ki-67 and Bax expression in the tumor tissues was assessed using immunohistochemistry. SH inhibited ESCC cell growth and markedly increased their radiosensitivity by inducing G2/M phase arrest. SH combined with radiation therapy significantly increased ESCC cell apoptosis. The molecular mechanism by which SH enhanced radiosensitivity of ESCC cells was related to Bcl-2, cyclin B1, CDK1, Ku86, Ku70, and Rad51 downregulation and Bax protein expression upregulation. SH combined with radiation considerably delayed the growth of tumor xenografts in vivo. Immunohistochemical analysis showed that in the SH combined with radiation group, the expression of Bax was significantly higher while that of Ki-67 was lower than the expressions in the control groups. Taken together, our findings showed that SH could improve the sensitivity of radiation in ESCC cells by inducing G2/M phase arrest, promoting radiation-induced apoptosis and inhibiting DSB-repair pathways. SH appears to be a prospective radiosensitizer for improving the efficacy of radiotherapy for ESCC.