Molecular effectors of radiation resistance in colorectal cancer

Evaluation of BMP-2 as a Differentiating and Radiosensitizing Agent for Colorectal Cancer Stem Cells

BACKGROUND

Despite effective clinical responses, a large proportion of patients undergo resistance to radiotherapy. The low response rate to current treatments in different stages of colorectal cancer depends on the prominent role of stem cells in cancer.

OBJECTIVE

In the present study, the role of BMP-2 as an ionizing radiation-sensitive factor in colorectal cancer cells was investigated.

METHODS

A sphere formation assay was used for the enrichment of HCT-116 cancer stem cells (CSCs). The effects of combination therapy (BMP-2+ radiation) on DNA damage response (DDR), proliferation, and apoptosis were evaluated in HCT-116 and CSCs. Gene expressions of CSCs and epithelialmesenchymal transition (EMT) markers were also evaluated.

RESULTS

We found that the sphere formation assay showed a significant increase in the percentage of CSCs. Moreover, expression of CSCs markers, EMT-related genes, and DNA repair proteins significantly decreased in HCT-116 cells compared to the CSCs group after radiation. In addition, BMP-2 promoted the radiosensitivity of HCT-116 cells by decreasing the survival rate of the treated cells at 2, 4, and 6 Gy compared to the control group in HCT-116 cells.

CONCLUSION

Our findings indicated that BMP-2 could affect numerous signaling pathways involved in radioresistance. Therefore, BMP-2 can be considered an appealing therapeutic target for the treatment of radioresistant human colorectal cancer.

Introducing novel key genes and transcription factors associated with rectal cancer response to chemoradiation through co-expression network analysis

Preoperative radiochemotherapy is a promising therapeutic method for locally advanced rectal cancer patients. However, the response of colorectal cancer (CRC) patients to preoperative radiotherapy varies widely. In this study, we aimed to identify novel biomarkers that could predict the response of colorectal tumors to treatment using a systems biology approach. We applied the Weighted Gene Co-Expression Network Analysis to construct co-expression networks and evaluated the correlation of these networks with radiation using the module-trait relationship. We then identified hub genes and related transcription factors in the selected co-expression module. Our analysis of seven constructed modules revealed that one module, which contained 113 nodes and 6066 edges, had the strongest correlation with radiation effects on CRC (correlation = 0.85; p-value = 6e-7). By analyzing the selected module with the CytoHubba plugin, we identified four hub genes, including ZEB2, JAM2, NDN, and PPAP2A. We also identified seven important transcription factors, including KLF4, SUZ12, TCF4, NANOG, POU5F1, SOX2, and SMARCA4, which may play essential roles in regulating the four hub genes. In summary, our findings suggest that ZEB2, JAM2, NDN, and PPAP2A, along with the seven transcription factors related to these hub genes, may be associated with the response of colorectal tumors to chemoradiotherapy.

The Pyroptotic and Nonpyroptotic Roles of Gasdermins in Modulating Cancer Progression and Their Perspectives on Cancer Therapeutics

Gasdermins (GSDMs) are a protein family encoded by six paralogous genes in humans, including GSDMA, GSDMB, GSDMC, GSDMD, GSDME (also known as DFNA5), and DFNB59 (also known as pejvakin). Structurally, members of the GSDM family possess a C-terminus (an autoinhibitory domain) and a positively charged N-terminus (a pore-forming domain) linked with divergent peptide linkers. Recently, GSDMs have been identified as key executors of pyroptosis (an immunogenic programmed cell death) due to their pore-forming activities on the plasma membrane when proteolytically cleaved by caspases or serine proteases. Accumulating studies suggest that chemoresistance is attributed to dysregulation of apoptotic machinery and that inducing pyroptosis to bypass aberrant apoptosis can potently resensitize apoptosis-resistant cancer to chemotherapeutics. Pyroptosis is initiated by pore formation and culminates with plasma membrane rupture; these processes enable the release of proinflammatory cytokines (e.g., IL-1β and IL-18) and damage-associated molecular patterns, which further modulate antitumor immunity within the tumor microenvironment. Although pyroptosis is considered a promising strategy to boost antitumor effects, it is also reported to cause unwanted tissue damage (e.g., gut damage and nephrotoxicity). Intriguingly, mounting evidence has uncovered nonpyroptotic roles of GSDMs in tumorigenesis, such as proliferation, invasion, metastasis, and drug resistance. Thus, this provides a rationale for GSDMs as potential therapeutic targets. Taken together, we shed unbiased light on the pyroptosis-dependent roles of GSDMs in cancer progression and highlighted how GSDMs modulate tumorigenesis in a pyroptosis-independent manner. It is evident that targeting GSDMs seems profound in cancer management; however, several problems require further investigation to target GSDMs from bench to bedside, which is elucidated in the discussion section.

Prognostic Impact of TP53 Mutations and Tumor Mutational Load in Colorectal Cancer

The DNA damage response (DDR) is critical for maintaining genome stability, and abnormal DDR—resulting from mutations in DNA damage-sensing and repair proteins—is a hallmark of cancer. Here, we aimed to investigate the predictive power of DDR gene mutations and the tumor mutational load (TML) for survival outcomes in a cohort of 22 rectal cancer patients who received pre-operative neoadjuvant therapy. Univariate analysis revealed that TML-high and TP53 mutations were significantly associated with worse overall survival (OS) with TML-high retaining significance in multivariate analyses. Kaplan–Meier survival analyses further showed TML-high was associated with worse disease-free (p = 0.036) and OS (p = 0.024) results in our patient cohort. A total of 53 somatic mutations were identified in 22 samples with eight (36%) containing mutations in DDR genes, including ATM, ATR, CHEK2, MRE11A, RAD50, NBN, ERCC2 and TP53. TP53 was the most frequently mutated gene, and TP53 mutations were significantly associated with worse OS (p = 0.023) in Kaplan–Meier survival analyses. Thus, our data indicate that TML and TP53 mutations have prognostic value for rectal cancer patients and may be important independent biomarkers for patient management. This suggests that prognostic determination for rectal cancer patients receiving pre-operative neoadjuvant therapy should include consideration of the initial TML and tumor genetic status.

Bioinformatic Analysis of the Effect of Silver Nanoparticles on Colorectal Cancer Cell Line

Colorectal cancer (CRC) is the most diagnosed cancer with the highest mortality rate each year globally. Although there are treatments for CRC, the development of resistance to therapies decreases the success of treatments. In vitro studies using the Caco-2 cell line have revealed the anticancer properties of silver nanoparticles (AgNPs) as a possible treatment for this disease. This study considered four researches that evaluated the proteomic profiles of cells of the Caco-2 line exposed to AgNPs. We performed a bioinformatics analysis to predict protein-protein interaction, hub genes, Gene Ontology (molecular function, biological process, and cellular components), KEGG pathways, analysis of expression, and immune cell infiltration. For these analyses, the STRING, DAVID, UALCAN, GEPIA2, and TISIDB databases were used. The results in Gene Ontology show that AgNPs cause a deregulation of genes related to cell-cell adhesion, the cytoplasm, the centriole, and carbon metabolism. Hub genes were identified, including GADPH, ENO1, EEF2, and ATP5A1, which showed differential expression in patients with adenocarcinoma of the colon and rectum. Additionally, the expression of the hub genes and immune cells was correlated. It was found that ATP5A1 and ENO1 were positively correlated with the infiltration of CD4+ T lymphocytes in colon adenocarcinoma and a negative correlation between GADPH and PDIA3 with the infiltration of NK cells and CD4+ T lymphocytes in rectal adenocarcinoma, respectively. In conclusion, the administration of AgNPs causes an alteration of biological processes, cellular components, metabolic pathways, deregulation of hub genes, and the activity of immune cells leading to a potential anticancer effect.

Fancy-Shaped Gold-Platinum Nanocauliflowers for Improved Proton Irradiation Effect on Colon Cancer Cells

Enhancing the effectiveness of colorectal cancer treatment is highly desirable. Radiation-based anticancer therapy—such as proton therapy (PT)—can be used to shrink tumors before subsequent surgical intervention; therefore, improving the effectiveness of this treatment is crucial. The addition of noble metal nanoparticles (NPs), acting as radiosensitizers, increases the PT therapeutic effect. Thus, in this paper, the effect of novel, gold–platinum nanocauliflowers (AuPt NCs) on PT efficiency is determined. For this purpose, crystalline, 66-nm fancy shaped, bimetallic AuPt NCs were synthesized using green chemistry method. Then, physicochemical characterization of the obtained AuPt NCs by transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDS), and UV-Vis spectra measurements was carried out. Fully characterized AuPt NCs were placed into a cell culture of colon cancer cell lines (HCT116, SW480, and SW620) and a normal colon cell line (FHC) and subsequently subjected to proton irradiation with a total dose of 15 Gy. The 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) test, performed after 18-h incubation of the irradiated cell culture with AuPt NCs, showed a significant reduction in cancer cell viability compared to normal cells. Thus, the radio-enhancing features of AuPt NCs indicate their potential application for the improvement in effectiveness of anticancer proton therapy.

Napabucasin (BBI 608), a potent chemoradiosensitizer in rectal cancer

BACKGROUND

The induction of reactive oxygen species (ROS) represents a viable strategy for enhancing the activity of radiotherapy. The authors hypothesized that napabucasin would increase ROS via its ability to inhibit NAD(P)H:quinone oxidoreductase 1 and potentiate the response to chemoradiotherapy in rectal cancer via distinct mechanisms.

METHOD

Proliferation studies, colony formation assays, and ROS levels were measured in HCT116 and HT29 cell lines treated with napabucasin, chemoradiation, or their combination. DNA damage (pγH2AX), activation of STAT, and downstream angiogenesis were evaluated in both untreated and treated cell lines. Finally, the effects of napabucasin, chemoradiotherapy, and their combination were assessed in vivo with subcutaneous mouse xenograft models.

RESULTS

Napabucasin significantly potentiated the growth inhibition of chemoradiation in both cell lines. Napabucasin increased ROS generation. Inhibition of ROS by N-acetylcysteine decreased the growth inhibitory effect of napabucasin alone and in combination with chemoradiotherapy. Napabucasin significantly increased pγH2AX in comparison with chemoradiotherapy alone. Napabucasin reduced the levels of pSTAT3 and VEGF and inhibited angiogenesis through an ROS-mediated effect. Napabucasin significantly potentiated the inhibition of growth and blood vessel formation by chemoradiotherapy in mouse xenografts.

CONCLUSION

Napabucasin is a radiosensitizer with a novel mechanism of action: increasing ROS production and inhibiting angiogenesis. Clinical trials testing the addition of napabucasin to chemoradiotherapy in rectal cancer are needed.

Pentagalloyl Glucose- and Ethyl Gallate-Rich Extract from Maprang Seeds Induce Apoptosis in MCF-7 Breast Cancer Cells through Mitochondria-Mediated Pathway

Bouea macrophylla Griffith, locally known as maprang, has important economic value as a Thai fruit tree. The maprang seed extract (MPSE) has been shown to exhibit antibacterial and anticancer activities. However, the bioactive constituents in MPSE and the molecular mechanisms underlying these anticancer activities remain poorly understood. This study aims to identify the active compounds in MPSE and to investigate the mechanisms involved in MPSE-induced apoptosis in MCF-7 treated cancer cells. The cytotoxic effect was determined by MTT assay. The apoptosis induction of MPSE was evaluated in terms of ROS production, mitochondrial membrane potential depolarization, and apoptosis-related gene expression. The compounds identified by HPLC and LC/MS analysis were pentagalloyl glucose, ethyl gallate, and gallic acid. MPSE treatment decreased cell proliferation in MCF-7 cells, and MPSE was postulated to induce G2/M phase cell cycle arrest. MPSE was found to promote intracellular ROS production in MCF-7 treated cells and to also influence the depolarization of mitochondrial membrane potential. In addition, MPSE treatment can lead to increase in the Bax/Bcl-2 gene expression ratio, suggesting that MPSE-induced apoptosis is mitochondria-dependent pathway. Our results suggest that natural products obtained from maprang seeds have the potential to target the apoptosis pathway in breast cancer treatments.

Aberrant Expression of RAD52, Its Prognostic Impact in Rectal Cancer and Association with Poor Survival of Patients

The DNA damage response enables cells to survive and maintain genome integrity. RAD52 is a DNA-binding protein involved in the homologous recombination in DNA repair, and is important for the maintenance of tumour genome integrity. We investigated possible correlations between RAD52 expression and cancer survival and response to preoperative radiotherapy. RAD52 expression was examined in tumour samples from 179 patients who underwent surgery for rectal cancer, including a sub-cohort of 40 patients who were treated with neoadjuvant therapy. A high score for RAD52 expression in the tumour centre was significantly associated with worse disease-free survival (DFS; p = 0.045). In contrast, reduced RAD52 expression in tumour centre samples from patients treated with neoadjuvant therapy (n = 40) significantly correlated with poor DFS (p = 0.025) and overall survival (OS; p = 0.048). Our results suggested that RAD52 may have clinical value as a prognostic marker of tumour response to neoadjuvant radiation and both disease-free status and overall survival in patients with rectal cancer.

MiR-185 enhances radiosensitivity of colorectal cancer cells by targeting IGF1R and IGF2

OBJECTIVE

Radioresistance is a significant obstacle for effective treatment of colorectal cancer (CRC). Recent studies have indicated that miR-185 inhibits proliferation, survival, and invasion of CRC; however, the role of this miRNA in radioresistance of CRC has not been identified yet. The aim of this study is to investigate the role of miR-185 in radiosensitivity of CRC.

METHODS

After transfecting the cells with mimic miR-185, expressions of IGF1R and IGF2 were evaluated by real-time PCR and western blot. The radiation response of transfected cells was also examined by colony forming assay. Sub-G1 fraction analysis through flow cytometry and caspase 3 activity was used to evaluate apoptosis.

RESULTS

The results of real-time PCR and western blot indicated that IGF1R and IGF2 are downregulated in the transfected cells. Colony forming assay revealed that transfected cells were more radiosensitive than other cells. On the other hand,following irradiation the rate of apoptosis was significantly higher in the transfected cells than in the other cells.

CONCLUSION

In summary, our study is the first to show that upregulation of miR-185 enhances the sensitivity of CRC cells to ionizing radiation. miR-185 may act as a novel biomarker of radioresistance and may clinically enhance the radiation response of CRC.

Targeted photodynamic therapy as potential treatment modality for the eradication of colon cancer and colon cancer stem cells

Colorectal cancer is commonly treated by tumour resection, as chemotherapy and radiation have proven to be less effective, especially if the tumour has metastasized. Resistance to therapies occurs in almost all patients with colorectal cancer, especially in those with metastatic tumours. Cancer stem cells have the ability to self-renew, and their slow rate of cycling enhances resistance to treatment and increases the likelihood of tumour recurrence. Most metastatic tumours are unable to be surgically removed, thus creating a need for treatment modalities that target cancers directly and destroy cancer stem cells. Photodynamic therapy involves a photosensitizer that when exposed to a light source of a particular wavelength becomes excited and produces a form of oxygen that kills cancer cells. Photodynamic therapy is currently being investigated as a treatment modality for colorectal cancer, and new studies are exploring enhancing photodynamic therapy efficacy with the aid of drug carriers and immune conjugates. These modifications could prove effective in targeting cancer stem cells that are thought to be resistant to photodynamic therapy. In order for photodynamic therapy to be an effective treatment in colorectal cancer, it requires treatment of both primary tumours and the metastatic secondary disease that is caused by colon cancer stem cells. This review focuses on current photodynamic therapy treatments available for colorectal cancer and highlights proposed actively targeted photosynthetic drug uptake mechanisms specifically mediated towards colon cancer stem cells, as well as identify the gaps in research which need to be investigated in order to develop a combinative targeted photodynamic therapy regime that can effectively control colorectal cancer primary and metastatic tumour growth by eliminating colon cancer stem cells.