Expression of Smac induced by the Egr1 promoter enhances the radiosensitivity of breast cancer cells

P300 Participates in Ionizing Radiation-Mediated Activation of Cathepsin L by Mutant p53

Our previous studies have shown that cathepsin L (CTSL) is involved in the ability of tumors to resist ionizing radiation (IR), but the specific mechanisms responsible for this remain unknown. We report here that mutant p53 (mut-p53) is involved in IR-induced transcription of CTSL. We found that irradiation caused activation of CTSL in mut-p53 cell lines, whereas there was almost no activation in p53 wild-type cell lines. Additionally, luciferase reporter gene assay results demonstrated that IR induced the p53 binding region on the CTSL promoter. We further demonstrated that the expression of p300 and early growth response factor-1 (Egr-1) was upregulated in mut-p53 cell lines after IR treatment. Accordingly, the expression of Ac-H3, Ac-H4, AcH3K9 was upregulated after IR treatment in mut-p53 cell lines, whereas histone deacetylase (HDAC) 4 and HDAC6 were reciprocally decreased. Moreover, knockdown of either Egr-1 or p300 abolished the binding of mut-p53 to the promoter of CTSL. Chromatin immunoprecipitation assay results showed that the IR-activated transcription of CTSL was dependent on p300. To further delineate the clinical relevance of interactions between Egr-1/p300, mut-p53, and CTSL, we accessed primary tumor samples to evaluate the relationships between mut-p53, CTSL, and Egr-1/p300 ex vivo. The results support the notion that mut-p53 is correlated with CTSL transcription involving the Egr-1/p300 pathway. Taken together, the results of our study revealed that p300 is an important target in the process of IR-induced transcription of CTSL, which confirms that CTSL participates in mut-p53 gain-of-function. SIGNIFICANCE STATEMENT: Transcriptional activation of cathepsin L by ionizing radiation required the involvement of mutated p53 and Egr-1/p300. Interference with Egr-1 or p300 could inhibit the expression of cathepsin L induced by ionizing radiation. The transcriptional activation of cathepsin L by p300 may be mediated by p53 binding sites on the cathepsin L promoter.

Transcriptome Analysis of MDA-MB-231 Cells Treated with Fumosorinone Isolated from Insect Pathogenic Fungi

BACKGROUND

In our previous study, we have isolated a new compound, named Fumosorinone (FU) from insect pathogenic fungi, and was found to inhibit proliferation, migration, and invasion of breast cancer MDA-MB-231 cells.

OBJECTIVE

The aim of this study was to identify the underlying molecular mechanisms for FU effects on MDAMB- 231 cells.

METHODS

After MDA-MB-231 cells were treated with FU for 48h, RNA sequencing was used to identify the effect of FU on the transcriptome of MDA-MB-231 cells. The validation of the relative expression of the selective genes was done using quantitative real-time PCR (qRT-PCR).

RESULTS

The transcriptome results showed that 2733 genes were differentially expressed between the untreated and the FU-treated cells, including 1614 up-regulated and 1119 down-regulated genes. The multiple genes are associated with cancer cell growth, migration, and invasion. Functional analysis identified multitude of pathways related to cancer, such as cell cycle, ECM-receptor interaction, p53 signaling pathway. We selected 4 upregulated and 9 downregulated genes, which are associated with breast cancer to verify their expression using qRT-PCR. The validation showed that HSD3B1, ALOX5, AQP5, COL1A2, CCNB1, CCND1, VCAM-1, PTPN1 and PTPN11 were significantly downregulated while DUSP1, DUSP5, GADD45A, EGR1 were upregulated in FU-treated MDA-MB-231cells.

CONCLUSION

These aberrantly expressed genes and pathways may play pivotal roles in the anti-cancer activity of FU, and maybe potential targets of FU treatments for TNBC. Further investigations are required to evaluate the FU mechanisms of anti-cancer action in vivo.

Bromocriptine and cabergoline induce cell death in prolactinoma cells via the ERK/EGR1 and AKT/mTOR pathway respectively

The treatment of hyperprolactinemia is based on the use of dopamine agonists, mainly bromocriptine (BRC) and cabergoline (CAB). They reduce tumour size effectively and restore gonadal function. However, there is a difference in drug sensitivity between CAB and BRC in patients with prolactinoma, although the underlying mechanisms are still unknown. Thus, we investigated whether there are differences in tumour sensitivity to CAB and BRC and their possible differential mechanisms in two prolactinoma cell lines. In our study, we found that GH3 cells are more sensitive to BRC and that MMQ cells are more sensitive to CAB. Moreover, BRC and CAB elicited cell death via different pathways; BRC induced prolactinoma cell death mainly through the apoptosis pathway, and CAB induced pituitary prolactinoma cell death mainly via the autophagic cell death pathway. Using gene microarray analysis, we found that BRC induces the apoptosis of prolactinoma cells through the ERK/EGR1 signalling pathway, whereas CAB induces autophagic death by inhibiting the AKT/mTOR signalling pathway. Our study showed the difference in tumour sensitivity and differential mechanisms in BRC- and CAB-treated prolactinoma cells, which provides a theoretical basis for the accurate treatment of prolactinoma.

Radiation-induced SOD2 overexpression sensitizes colorectal cancer to radiation while protecting normal tissue

This study investigated whether radiation-induced overexpression of superoxide dismutase 2 (SOD2) exerts radio-sensitizing effects on tumor cells while having radio-protective effects on normal cells during radio-activated gene therapy for human colorectal cancer. A chimeric promoter, C9BC, was generated by directly linking nine tandem CArG boxes to a CMV basic promoter, after which lentiviral vectors containing GFP and SOD2 gene driven by the C9BC promoter were constructed. Stably transfected HT-29 colorectal cancer cells and CCD 841 CoN normal colorectal cells were irradiated to a dose of 6-Gy, and cell proliferation and apoptosis were observed. Tumor xenografts and peritumoral skin tissue in BALB/c mice were infected with the therapeutic lentivirus and subsequently irradiated with a total dose of 6 Gy. In vitro experiments revealed that radiation-induced SOD2 overexpression inhibited tumor cell proliferation (61.89% vs. 40.17%, P < 0.01) and decreased apoptosis among normal cells (14.8% vs. 9.6%, P = 0.02) as compared to untransfected cells. Similar effects were observed in vivo. Thus radiation-induced SOD2 overexpression via the chimeric C9BC promoter increased the radiosensitivity of HT-29 human colorectal cancer cells and concurrently protected normal CCD 841 CoN colorectal cells from radiation damage.

Comprehensive tissue-specific gene set enrichment analysis and transcription factor analysis of breast cancer by integrating 14 gene expression datasets

Breast cancer is the most commonly diagnosed malignancy in women. Several key genes and pathways have been proven to correlate with breast cancer pathology. This study sought to explore the differences in key transcription factors (TFs), transcriptional regulation networks and dysregulated pathways in different tissues in breast cancer. We employed 14 breast cancer datasets from NCBI-GEO and performed an integrated analysis in three different tissues including breast, blood and saliva. The results showed that there were eight genes (CEBPD, EGR1, EGR2, EGR3, FOS, FOSB, ID1 and NFIL3) down-regulated in breast tissue but up-regulated in blood tissue. Furthermore, we identified several unreported tissue-specific TFs that may contribute to breast cancer, including ATOH8, DMRT2, TBX15 and ZNF367. The dysregulation of these TFs damaged lipid metabolism, development, cell adhesion, proliferation, differentiation and metastasis processes. Among these pathways, the breast tissue showed the most serious impairment and the blood tissue showed a relatively moderate damage, whereas the saliva tissue was almost unaffected. This study could be helpful for future biomarker discovery, drug design, and therapeutic and predictive applications in breast cancers.

TRAIL overexpression co-regulated by Egr1 and HRE enhances radiosensitivity of hypoxic A549 cells depending on its apoptosis inducing role

Ionizing radiation can upregulate the expression levels of TRAIL and enhance tumor cell apoptosis. While Early growth response 1 (Egr1) gene promoter has radiation inducible characteristics, the expression for exogenous gene controlled by Egr1 promoter could be enhanced by ionizing radiation, but its efficiency is limited by tissue hypoxia. Hypoxia response elements (HREs) are important hypoxic response regulatory sequences and sensitivity enhancers. Therefore, we chose TRAIL as the gene radiotherapy to observe whether it is regulated by Egr1 and HER and its effects on A549 cells and its mechanism. The pcDNA3.1-Egr1-TRAIL (pc-E-hsT) and pcDNA3.1-HRE/Egr1-TRAIL (pc-H/E-hsT) plasmids containing Egr1-hsTRAIL and HRE/Egr1-hsTRAIL were transfected into A549 cells, the cells were treated by hypoxia and radiation. The TRAIL mRNA in the cells and protein concentration in the culture supernatants were measured by RT-PCR and ELISA, respectively. Mean lethal dose D0 value was evaluated with colony forming assay. The cell apoptotic rates were analyzed by FCM and TUNEL assay. Expression of DR4, DR5 and cleaved caspase-3 proteins were analyzed by western blotting. It showed that TRAIL mRNA expression and TRAIL concentration all significantly increased under hypoxia and/or radiation. D0 value of pc-H/E‑hsT transfected cells under hypoxia was lowest, indicating more high radiosensitivity. Hypoxia could not cause the pc-E-hsT transfected cell apoptotic rate increase, but there were promoting effects in pc-H/E-hsT transfected cells. DR4 had not obvious change in pc-E-hsT and pc-H/E-hsT transfected cells under normoxic and hypoxic condition, otherwise, DR5 and cleaved caspase-3 increased mostly in pc-H/E-hsT transfected cells under hypoxic condition. TRAIL overexpression was co-regulated by Egr1 and HRE. TRAIL might promote hypoxic A549 cell radiosensitivity and induce apoptosis depending on DR5 to caspase-3 pathways.

Clinical significance of joint detection of Smac and Caspase9 protein levels in predicting preoperative chemoradiotherapy sensitivity in patients with rectal cancer

AIM: To evaluate the role of second mitochondria-derived activator of Caspase (Smac) and cysteinyl asparate specific proteinase 9 (Caspase9), alone and in combination, in predicting preoperative chemoradiotherapy sensitivity in patients with rectal carcinoma by investigating the relationship between the expression of Smac and Caspase9 and the pathologic response in patients who have received preoperative chemoradiotherapy.

METHODS: The biopsy specimens before chemoradiotherapy and surgical specimens were obtained from 43 cases of rectal adenocarcinoma who received preoperative chemoradiotherapy from July 2008 to June 2013. Immunohistochemical staining was used to test the protein expression levels of Smac and Caspase9, and the relationship between Smac and Caspase9 protein expression levels and postoperative pathological response was analyzed.

RESULTS: The effective rate of preoperative chemoradiotherapy was as high as 72.1%, and the pathological complete response rate was 30.2%. The expression of Smac and Caspase9 was altered after chemoradiotherapy (P < 0.001 for both). Their expression levels were significantly downregulated after chemoradiotherapy. The effective rate of preoperative chemoradiotherapy was significantly increased in patients who were positive for Caspase9 protein expression (staining score range, 1 to 8) before chemoradiotherapy (P < 0.05). And the effective rate was further increased when Smac and Caspase9 proteins were both positive (P = 0.0002). The survival analysis indicated that chemoradiotherapy response was correlated with the overall survival, and the survival was significantly longer in the response arm than in the non-response arm (P = 0.0193).

CONCLUSION: The positive expression of Caspase9 protein in biopsy specimens before chemoradiotherapy can be a marker for sensitivity to radiation and chemotherapy in patients with rectal cancer. Joint detection of Smac and Caspase9 proteins can be more reliable in predicting the sensitivity to preoperative chemoradiotherapy in rectal cancer patients. The response to chemoradiotherapy is a key factor responsible for patients' prognosis. The joint detection of Smac and Caspase9 can be helpful in screening out patients who are sensitive to preoperative chemoradiation.

Enhancement of silencing DNA polymerase β on the radiotherapeutic sensitivity of human esophageal carcinoma cell lines

Human DNA polymerase β (DNA polymeraseβ (polβ)) is a small monomeric protein which is essential for short-patch base excision repair (BER). It plays an important role in regulating the radiation sensitivity of tumor cells in the course of tumor radiation therapy. In this study, qRT-PCR and Western blot assays were used to quantify polβ expression levels in esophageal carcinoma (EC) cells that were transfected with polβ small interfering RNA (siRNA). Cell counting Kit-8 (CCK-8), flow cytometry, and Hoechst/PI stain assays were conducted to evaluate the effects of silencing polβ on the radiotherapeutic sensitivity of EC cells. We found that the expression levels of polβ in EC cells were significantly decreased after transfection with polβ siRNA. Then, we found that polβ silencing increased the sensitivity of EC cells to radiation therapy. In conclusion, our study paves the way for a better understanding of the mechanism of the polβ gene in DNA repair, and we propose that RNA interference technology will have important applications in gene therapy of EC and other cancers in the future.