Mitochondrial fission determines cisplatin sensitivity in tongue squamous cell carcinoma through the BRCA1-miR-593-5p-MFF axis

Different impact of vitamin D on mitochondrial activity and morphology in normal and malignant keratinocytes, the role of genomic pathway

Deregulation of mitochondria activity is one of the hallmarks of cancerogenesis and an important target for cancer therapy. Therefore, we compared the impact of an active form of vitamin D3 (1,25(OH)2D3) on mitochondrial morphology and bioenergetics in human squamous cell carcinoma (A431) and immortalized HaCaT keratinocytes. It was shown that mitochondria of cancerous A431 cells differ from that observed in HaCaT keratinocytes in terms of network, morphology, bioenergetics, glycolysis, and mitochondrial DNA copy number, while treatment of A431 with 1,25(OH)2D3 partially eliminates these differences. Furthermore, mitochondrial membrane potential, basal respiration, and mitochondrial reactive oxygen species production were decreased in A431 cells treated with 1,25(OH)2D3. Additionally, the expression and protein level of mitophagy marker PINK1 was significantly increased in A431 1,25(OH)2D3 treated cells, but not observed in treated HaCaT cells. Knockout of VDR (vitamin D receptor) or RXRA (binding partner retinoid X receptor) partially altered mitochondrial morphology and function as well as mitochondrial response to 1,25(OH)2D3. Transcriptomic analysis on A431 cells treated with 1,25(OH)2D3 revealed modulation of expression of several mitochondrial-related genes involved in mitochondrial depolarization, mitochondrial protein translation (i.e. LYRM9, MARS2), and fusion-fission (OPA1, FIS1, MFN1 and 2), however, none of the genes coded by mitochondrial DNA was affected. Interestingly, in silico analyses of nuclear-encoded mitochondrial genes revealed that they are rather activated by the secondary genomic response to 1,25(OH)2D3. Taken together, 1,25(OH)2D3 remodels mitochondrial architecture and bioenergetics through VDR-dependent and only partially RXRA-dependent activation of the genomic pathway, thus outlining a new perspective for anticancer properties of vitamin D3 in relation to mitochondria in squamous cell carcinoma.

Plumbagin has an inhibitory effect on the growth of TSCC PDX model and it enhances the anticancer efficacy of cisplatin

BACKGROUND

Head and neck squamous cell carcinomas are the sixth most common malignant tumors worldwide. Tongue squamous cell carcinoma is a common malignant tumor of this type, and it is associated with poor prognosis, a high rate of recurrence and a low survival rate. Plumbagin is derived from Plumbago zeylanica L, several studies report that plumbagin could inhibit cell, tumor metastasis, induce apoptosis in various cancer cells. Patient-derived xenograft (PDX) model can maintain the heterogeneity and microenvironment of human tumors, is a powerful research tool for developing potentially effective therapies for TSCC.

METHODS

Tumor tissues obtained from TSCC patients were implanted into immunodeficient mice to establish TSCC PDX models. Subsequently, the PDX models were used to evaluate the anti-tumor effects of plumbagin on TSCC. Furthermore, we conducted next-generation sequencing (NGS) and explored the mRNA expression profiles between the treatment and control groups. We selected eight mRNAs related to the characteristics and prognosis of TSCC patients for further analysis.

RESULTS

Plumbagin could inhibit the growth of TSCC PDX models and inhibit expression of Akt/mTOR pathway. In addition, plumbagin was shown to increase drug sensitivity to cisplatin. The eight mRNAs selected for further analysis, AXL, SCG5, VOPP1, DCBLD2 and DRAM1 are cancer-promoting genes, DUSP1, AQP5 and BLNK are cancer suppressor genes. And they were related to the diagnosis, growth, prognosis, and immune cell infiltration in TSCC patients.

CONCLUSION

Plumbagin exhibits an inhibitory effect on the growth of the PDX model of TSCC. Moreover, plumbagin enhances the inhibitory effects of cisplatin.

The ELK3-DRP1 axis determines the chemosensitivity of triple-negative breast cancer cells to CDDP by regulating mitochondrial dynamics

Triple-negative breast cancer (TNBC) is the most lethal form of breast cancer. TNBC patients have higher rates of metastasis and restricted therapy options. Although chemotherapy is the conventional treatment for TNBC, the frequent occurrence of chemoresistance significantly lowers the efficacy of treatment. Here, we demonstrated that ELK3, an oncogenic transcriptional repressor that is highly expressed in TNBC, determined the chemosensitivity of two representative TNBC cell lines (MDA-MB231 and Hs578T) to cisplatin (CDDP) by regulating mitochondrial dynamics. We observed that the knockdown of ELK3 in MDA-MB231 and Hs578T rendered these cell lines more susceptible to the effects of CDDP. We further demonstrated that the chemosensitivity of TNBC cells was caused by the CDDP-mediated acceleration of mitochondrial fission, excessive mitochondrial reactive oxygen species production, and subsequent DNA damage. In addition, we identified DNM1L, a gene encoding the dynamin-related protein 1 (a major regulator of mitochondrial fission), as a direct downstream target of ELK3. Based on these results, we propose that the suppression of ELK3 expression could be used as a potential therapeutic strategy for overcoming the chemoresistance or inducing the chemosensitivity of TNBC.

MiRNAs Action and Impact on Mitochondria Function, Metabolic Reprogramming and Chemoresistance of Cancer Cells: A Systematic Review

MicroRNAs (miRNAs) are involved in the regulation of mitochondrial function and homeostasis, and in the modulation of cell metabolism, by targeting known oncogenes and tumor suppressor genes of metabolic-related signaling pathways involved in the hallmarks of cancer. This systematic review focuses on articles describing the role, association, and/or involvement of miRNAs in regulating the mitochondrial function and metabolic reprogramming of cancer cells. Following the PRISMA guidelines, the articles reviewed were published from January 2010 to September 2022, with the search terms "mitochondrial microRNA" and its synonyms (mitochondrial microRNA, mitochondrial miRNA, mito microRNA, or mitomiR), "reprogramming metabolism," and "cancer" in the title or abstract). Thirty-six original research articles were selected, revealing 51 miRNAs with altered expression in 12 cancers: bladder, breast, cervical, colon, colorectal, liver, lung, melanoma, osteosarcoma, pancreatic, prostate, and tongue. The actions of miRNAs and their corresponding target genes have been reported mainly in cell metabolic processes, mitochondrial dynamics, mitophagy, apoptosis, redox signaling, and resistance to chemotherapeutic agents. Altogether, these studies support the role of miRNAs in the metabolic reprogramming hallmark of cancer cells and highlight their potential as predictive molecular markers of treatment response and/or targets that can be used for therapeutic intervention.

Non-Coding RNA-Dependent Regulation of Mitochondrial Dynamics in Cancer Pathophysiology

Mitochondria are essential organelles which dynamically change their shape and number to adapt to various environmental signals in diverse physio-pathological contexts. Mitochondrial dynamics refers to the delicate balance between mitochondrial fission (or fragmentation) and fusion, that plays a pivotal role in maintaining mitochondrial homeostasis and quality control, impinging on other mitochondrial processes such as metabolism, apoptosis, mitophagy, and autophagy. In this review, we will discuss how dysregulated mitochondrial dynamics can affect different cancer hallmarks, significantly impacting tumor growth, survival, invasion, and chemoresistance. Special emphasis will be given to emerging non-coding RNA molecules targeting the main fusion/fission effectors, acting as novel relevant upstream regulators of the mitochondrial dynamics rheostat in a wide range of tumors.

A Heterozygous Mutation in MFF Associated with a Mild Mitochondrial Phenotype

BACKGROUND

The number of mutations in nuclear encoded genes causing mitochondrial disease is ever increasing. Identification of these mutations is particularly important in the diagnosis of neuromuscular disorders as their presentation may mimic other acquired disorders.We present a novel heterozygous variant in mitochondrial fission factor (MFF) which mimics myasthenia gravis.

OBJECTIVE

To determine if the MFF c.937G>A, p.E313K variant causes a mild mitochondrial phenotype.

METHODS

We used whole exome sequencing (WES) to identify a novel heterozygous variant in MFF in a patient with ptosis, fatigue and muscle weakness. Using patient derived fibroblasts, we performed assays to evaluate mitochondrial and peroxisome dynamics.

RESULTS

We show that fibroblasts derived from this patient are defective in mitochondrial fission, despite normal recruitment of Drp1 to the mitochondria.

CONCLUSIONS

The MFF c.937G>A, p.E313K variant leads to a mild mitochondrial phenotype and is associated with defective mitochondrial fission in patient-derived fibroblasts.

BRCA1 transports the DNA damage signal for CDDP-induced centrosome amplification through the centrosomal Aurora A

Breast cancer gene 1 (BRCA1) plays roles in DNA repair and centrosome regulation and is involved in DNA damage-induced centrosome amplification (DDICA). Here, the centrosomal localization of BRCA1 and the kinases involved in centrosome duplication were analyzed in each cell cycle phase after treatment with DNA crosslinker cisplatin (CDDP). CDDP treatment increased the centrosomal localization of BRCA1 in early S-G2 phase. BRCA1 contributed to the increased centrosomal localization of Aurora A in S phase and that of phosphorylated Polo-like kinase 1 (PLK1) in late S phase after CDDP treatment, resulting in centriole disengagement and overduplication. The increased centrosomal localization of BRCA1 and Aurora A induced by CDDP treatment involved the nuclear export of BRCA1 and BRCA1 phosphorylation by ataxia telangiectasia mutated (ATM). Patient-derived variants and mutations at phosphorylated residues of BRCA1 suppressed the interaction between BRCA1 and Aurora A, as well as the CDDP-induced increase in the centrosomal localization of BRCA1 and Aurora A. These results suggest that CDDP induces the phosphorylation of BRCA1 by ATM in the nucleus and its transport to the cytoplasm, thereby promoting the centrosomal localization Aurora A, which phosphorylates PLK1. The function of BRCA1 in the translocation of the DNA damage signal from the nucleus to the centrosome to induce centrosome amplification after CDDP treatment might support its role as a tumor suppressor.

MTP18 inhibition triggers mitochondrial hyperfusion to induce apoptosis through ROS-mediated lysosomal membrane permeabilization-dependent pathway in oral cancer

Although stress-induced mitochondrial hyperfusion (SIMH) exerts a protective role in aiding cell survival, in the absence of mitochondrial fission, SIMH drives oxidative stress-related induction of apoptosis. In this study, our data showed that MTP18, a mitochondrial fission-promoting protein expression, was increased in oral cancer. We have screened and identified S28, a novel inhibitor of MTP18, which was found to induce SIMH and subsequently trigger apoptosis. Interestingly, it inhibited MTP18-mediated mitochondrial fission, as shown by a decrease in p-Drp1 along with increased Mfn1 expression in oral cancer cells. Moreover, S28 induced autophagy but not mitophagy due to the trouble in engulfment of hypoperfused mitochondria. Interestingly, S28-mediated SIMH resulted in the loss of mitochondrial membrane potential, leading to the consequent generation of mitochondrial superoxide to induce intrinsic apoptosis. Mechanistically, S28-induced mitochondrial superoxide caused lysosomal membrane permeabilization (LMP), resulting in decreased lysosomal pH, which impaired autophagosome-lysosome fusion. In this setting, it showed that overexpression of MTP18 resulted in mitochondrial fission leading to mitophagy and inhibition of superoxide-mediated LMP and apoptosis. Further, S28, in combination with FDA-approved anticancer drugs, exhibited higher apoptotic activity and decreased cell viability, suggesting the MTP18 inhibition combined with the anticancer drug could have greater efficacy against cancer.

5-Methoxytryptophan Sensitizing Head and Neck Squamous Carcinoma Cell to Cisplatitn Through Inhibiting Signal Transducer and Activator of Transcription 3 (STAT3)

Head and neck squamous cell carcinoma (HNSCC) is a common cancer of the oral cavity. Cisplatin (CDDP) is the ideal chemo-radiotherapy used for several tumor types, but resistance to the drug has become a major obstacle in treating patients with HNSCC. 5-methoxytryptophan (5-MTP), a 5-methoxyindole metabolite of tryptophan metabolism, reduces inflammation-mediated proliferation and metastasis. This study aimed to assess the anti-oral cancer activity of 5-MTP when used alone or in combination with CDDP. Results showed that CDDP dose dependently reduced the growth of SSC25 cells but not 5-MTP. The combination of CDDP and 5-MTP exerted additional inhibitory effect on the growth of SSC25 cells by attenuating the phosphorylation of STAT3. In the 4-nitroquinoline-1-oxide-induced oral cancer mouse model, 5-MTP sensitized the reduction effect of CDDP on tumorigenesis, which restricted the tongue tissue in hyperkeratotic lesion rather than squamous cell carcinoma. The combination of CDDP and 5-MTP may be a potent therapeutic strategy for HNSCC patients with radiotherapy.

Mitochondrial Genetic and Epigenetic Regulations in Cancer: Therapeutic Potential

Mitochondria are dynamic organelles managing crucial processes of cellular metabolism and bioenergetics. Enabling rapid cellular adaptation to altered endogenous and exogenous environments, mitochondria play an important role in many pathophysiological states, including cancer. Being under the control of mitochondrial and nuclear DNA (mtDNA and nDNA), mitochondria adjust their activity and biogenesis to cell demands. In cancer, numerous mutations in mtDNA have been detected, which do not inactivate mitochondrial functions but rather alter energy metabolism to support cancer cell growth. Increasing evidence suggests that mtDNA mutations, mtDNA epigenetics and miRNA regulations dynamically modify signalling pathways in an altered microenvironment, resulting in cancer initiation and progression and aberrant therapy response. In this review, we discuss mitochondria as organelles importantly involved in tumorigenesis and anti-cancer therapy response. Tumour treatment unresponsiveness still represents a serious drawback in current drug therapies. Therefore, studying aspects related to genetic and epigenetic control of mitochondria can open a new field for understanding cancer therapy response. The urgency of finding new therapeutic regimens with better treatment outcomes underlines the targeting of mitochondria as a suitable candidate with new therapeutic potential. Understanding the role of mitochondria and their regulation in cancer development, progression and treatment is essential for the development of new safe and effective mitochondria-based therapeutic regimens.

Mitochondrial fission factor promotes cisplatin resistancein hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver tumor and one of the leading causes of cancer-related death worldwide. Chemotherapeutic agents/regimens such as cisplatin (DDP) are frequently used for advanced HCC treatment. However, drug resistance remains a major hindrance and the underline mechanisms are not fully understood. In this study, we investigated the expression pattern and function of mitochondrial fission factor (Mff) in cisplatin-resistant HCC. We found that Mff is highly expressed in cisplatin-resistant HCC tissues and cell lines. Knockdown of Mff suppresses cell proliferation and promotes cell apoptosis of HCC/DDP cells. In addition, knockdown of Mff sensitizes Huh-7/DDP cells to cisplatin treatment, inhibits cell proliferation, migration and invasion, and enhances cell apoptosis. Confocal imaging showed that knockdown of Mff inhibits the mitochondrial fission and downregulates the expression of GTPase dynamin-related protein 1 (Drp1) in cisplatin-resistant Huh-7/DDP cells. Moreover, xenograft tumor model revealed that knockdown of Mff sensitizes Huh-7/DDP xenograft tumor to cisplatin treatment . In summary, our findings suggest that Mff regulates mitochondrial Drp1 expression and promotes cisplatin resistance in HCC, which provides a potential therapeutic target for the treatment of resistant HCC.

LncRNAs and miRNAs participate in determination of sensitivity of cancer cells to cisplatin

Cisplatin is an extensively used chemotherapeutic substance for various types of human malignancies including sarcomas, carcinomas and lymphomas. Yet, the vast application of this drug is hampered by the emergence of chemoresistance in some treated patients. Several mechanisms such as degradation of the membrane transporters by cisplatin have been implicated in the pathogenesis of this event. Recent researches have also indicated the role of long non-coding RNAs (lncRNAs) as well as micoRNAs (miRNAs) in the emergence of resistance to cisplatin in several cancer types. For instance, up-regulation of miR-21 has been associated with resistance to this agent in ovarian cancer, oral squamous cell cancer, gastric malignancy and non-small cell lung cancer (NSCLC). On the other hand, down-regulation of miR-218 has been implicated in emergence of chemoresistance in breast cancer and esophageal squamous cell carcinoma. MALAT1 is implicated in the chemoresistance of bladder cancer cells, NSCLC, gastric cancer and cervical cancer. Most notably, the expression profile of resistance-associated miRNAs and lncRNAs can predict overall survival of cancer patients. Mechanistic assays have revealed that interference with expression of some miRNAs and lncRNAs can reverse the resistance phenotype in cancer cells. In this paper, we review the scientific writings on the role of lncRNAs and miRNAs in the evolution of chemoresistance to cisplatin in cancer cells.

Screening Circular RNAs Related to Acquired Gefitinib Resistance in Non-small Cell Lung Cancer Cell Lines

Background: Gefitinib is a tyrosine kinase inhibitor (TKI) of epidermal growth factor receptor (EGFR) used to treat EGFR mutation-positive patients with non-small cell lung cancer (NSCLC). However, the efficacy of gefitinib is limited by the development of acquired resistance. Studies have shown that circular RNAs (circRNAs) are involved in the acquired resistance to many anticancer agents. However, the expression profiles and functions of circRNAs in gefitinib resistance in NSCLC are poorly understood so far. Methods: In this study, circRNA expression profiling was explored in two gefitinib-resistant NSCLC cell lines (HCC827/GR and PC9/GR) and their parental sensitive cells (HCC827 and PC9) using high-throughput RNA sequencing. Quantitative real-time PCR (qRT-PCR) was used to confirm the expression of selected differentially expressed circRNAs. Bioinformatic tools including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), network analysis, and Kaplan-Meier plotter database were used to predict the functions and pathways of these differentially expressed circRNAs. Results: We identified 46 and 56 differentially expressed circRNAs in HCC827/GR and PC9/GR cell lines, respectively, compared with those in their parental cell lines. Gene ontology and KEGG pathway analysis identified that the host linear transcripts of these differentially expressed circRNAs were involved in many critical biological pathways and molecular functions. We found that hsa_circ_0000567 was consistently up-regulated, and hsa_circ_0006867 was consistently down-regulated in two resistant cell lines. We further used hsa_circ_0000567 and hsa_circ_0006867 as key circRNAs to construct circRNA-miRNA-mRNA networks. Several target mRNAs of these two circRNAs had been shown to significantly associate with the overall survival of patients with lung cancer. Conclusions: In this study, we generated the comprehensive expression and functional profiles of the differentially expressed circRNAs between gefitinib-resistant and -sensitive NSCLC cells, and showed that dysregulation of circRNAs might play an important role in the development of acquired resistance to gefitinib in NSCLC.

miR-593-5p inhibit cell proliferation by targeting PLK1 in non small cell lung cancer cells

Worldwide, lung cancer has the highest rates of mortality and morbidity, with the majority of its pathology attributable to non-small cell lung cancer (NSCLC). MicroRNAs are pivotal in the occurrence and development of cancer. However, the role of miRNA-593-5p in the progression of NSCLC is not clear. In this study, we investigate, in vitro, whether miRNA-593-5p inhibits NSCLC cell proliferation. To clarify its specific mechanism of inhibition, we used bioinformatics to predict its target genes and identified PLK1. Luciferase reporter assay confirmed the binding of miR-593-5p to the PLK1 3'-UTR in a sequence-specific manner in NSCLC cells. Additionally, we also found through Western blot and quantitative RT-PCR that miR-593-5p down-regulates the expression of PLK1 protein. Finally, PLK1 overexpression was shown to disinhibit NSCLC cell proliferation. Taken together, this evidence suggests that miR-593-5p inhibits NSCLC cell proliferation by inhibiting PLK1 expression.

The miR-372-ZBTB7A Oncogenic Axis Suppresses TRAIL-R2 Associated Drug Sensitivity in Oral Carcinoma

miR-372 has been shown a potent oncogenic miRNA in the pathogenesis of oral squamous cell carcinoma (OSCC). The zinc finger and BTB domain containing 7A protein (ZBTB7A) is a transcriptional regulator that is involved in a great diversity of physiological and oncogenic regulation. However, the modulation of ZBTB7A in OSCC remains unclear. Tissue analysis identifies a reverse correlation in expression between miR-372 and ZBTB7A in OSCC tumors. When OSCC cells have stable knockdown of ZBTB7A, their oncogenic potential and drug resistance is increased. By way of contrast, such an increase is attenuated by expression of ZBTB7A. Screening and validation confirms that ZBTB7A is able to modulate expression of the death receptors TRAIL-R1, TRAIL-R2, Fas and p53 phosphorylated at serine-15. In addition, ZBTB7A transactivates TRAIL-R2, which sensitizes cells to cisplatin-induced apoptosis. The ZBTB7A-TRAIL-R2 cascade is involved in both the extrinsic and intrinsic cisplatin-induced pathways of apoptosis. Database analysis indicates that the expression level of and the copy status of ZBTB7A and TRAIL-R2 are important survival predictors for head and neck cancers. Collectively, this study indicates the importance of the miR-372-ZBTB7A-TRAIL-R2 axis in mediating OSCC pathogenesis and in controlling OSCC drug resistance. Therefore, silencing miR-372 and/or upregulating ZBTB7A would seem to be promising strategies for enhancing the sensitivity of OSCC to cisplatin therapy.

lncRNA CISAL Inhibits BRCA1 Transcription by Forming a Tertiary Structure at Its Promoter

Cisplatin-based neoadjuvant chemotherapy has been shown to improve survival in patients with squamous cell carcinoma (SCC), but clinical biomarkers to predict chemosensitivity remain elusive. Here, we show the long noncoding RNA (lncRNA) LINC01011, which we termed cisplatin-sensitivity-associated lncRNA (CISAL), controls mitochondrial fission and cisplatin sensitivity by inhibiting BRCA1 transcription in tongue SCC (TSCC) models. Mechanistically, we found CISAL directly binds the BRCA1 promoter and forms an RNA-DNA triplex structure, sequestering BRCA1 transcription factor-GABPA away from the downstream regulatory binding region. Importantly, the clinical relevance of these findings is suggested by the significant association of CISAL and BRCA1 expression levels in TSCC tumors with neoadjuvant chemosensitivity and overall survival. We propose a new model where lncRNAs are tethered at gene promoter by RNA-DNA triplex formation, spatially sequestering transcription factors away from DNA-binding sites. Our study uncovers the potential of CISAL-BRCA1 signaling as a potential target to predict or improve chemosensitivity.

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CISAL enhances mitochondrial fission and cisplatin sensitivity in TSCC cells through BRCA1

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CISAL directly binds the BRCA1 promoter and forms an RNA-DNA triplex structure

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CISAL sequesters GABPA away from regulatory binding at BRCA1 promoter

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High CISAL predicts favorable neoadjuvant chemosensitivity and prognosis of TSCC patients

MTFP1 overexpression promotes the growth of oral squamous cell carcinoma by inducing ROS production

Mitochondrial fission process 1 (MTFP1) is a novel nuclear-encoded protein that promotes mitochondrial fission. Increasing lines of evidence indicate that increased mitochondrial fission is involved in carcinogenesis and tumor progression. However, the expression and biological effects of MTFP1 in cancer development is still unclear, especially in oral squamous cell carcinoma (OSCC). In this study, we first evaluated the expression of MTFP1 in 12-paired OSCC tumor and peritumor tissues. We then explored the effects of MTFP1 knockdown or overexpression on cell growth by cell proliferation, colony formation, cell cycle, and cell apoptosis assays. Furthermore, the mechanisms by which MTFP1 promoted OSCC cell growth were explored. Our results showed that MTFP1 is frequently overexpressed in OSCC tissues. Functional experiments revealed that MTFP1 promoted the growth of OSCC cells by inducing the progression of cell cycle and suppressing cell apoptosis. Mechanistically, MTFP1 overexpression-mediated mitochondrial fragmentation and subsequent ROS production was found to be involved in the promotion of OSCC cell growth. Collectively, our study demonstrates that MTFP1 plays a critical oncogenic role in OSCC carcinogenesis, which may serve as a potential therapeutic target in the treatment of this malignance.

miR‑593 inhibits proliferation and invasion and promotes apoptosis in non‑small cell lung cancer cells by targeting SLUG‑associated signaling pathways

Increasing evidence suggests that microRNAs (miRNAs or miRs) serve a critical role in tumor development. However, the role of miRNAs in non-small cell lung cancer (NSCLC) progression remains largely unknown. The present study observed that miR-593 was significantly impaired in patients with NSCLC and was a novel regulator of NSCLC progression. Patients whose tumors had high expression levels of miR-593 had longer overall survival than patients whose tumors had low levels of miR-593 expression (P=0.0219). miR-593 expression levels were inversely correlated with zinc finger protein SNAI2 (SLUG) messenger RNA (mRNA) levels in 87 clinical tissue specimens of NSCLC (P<0.001). A luciferase assay demonstrated that miR-593 interacted with the binding sites present in the SLUG 3′-untranslated region and reduced the expression of SLUG. Introduction of a miR-593 mimic suppressed cell proliferation by inactivating the SLUG/protein kinase B (Akt)/cyclin D1/CDK4 or CDK6 signaling pathway, while it induced apoptosis by activating the SLUG/Akt/Bcl-2/BAX signaling pathway. Furthermore, introduction of a miR-593 mimic recovered the expression of E-cadherin at the protein and mRNA level, and inhibited cell migration and invasion. In conclusion, these results indicated that miR-593 may act as a tumor suppressor in NSCLC to decelerate cancer aggressiveness by inhibiting SLUG expression.

Photobiomodulation Enhances Cisplatin Cytotoxicity in a Culture Model with Oral Cell Lineages

Cisplatin plays a central role in cancer chemotherapy, but resistance to this drug remains a major obstacle in treatment. Drawbacks related to cisplatin failure may be associated with cell energy metabolism. This study investigated whether photobiomodulation (PBM) can potentiate the effects of cisplatin on keratinocytes (HaCat) and cancer cells (SCC25 and HN12). Cells were treated with laser (GaAlAs; 660 nm; 60 mW; 0.33 J; 2.14 W cm^-2 ; 11.7 J cm^-2 and 6 s) and cisplatin (7.8 μg mL^-1 ) to evaluate cell viability, Ki-67, VEGF, TGF-β1, EGF expression and ROS production. Observations were validated in the SCC25 cell lineage, where the type of cell death (necrosis/apoptosis) and the amount of ATP were assessed. Cell lineages showed increased sensitivity to cisplatin associated with PBM (Cis-PBM). Ki-67 was augmented in all cell lineages treated with Cis-PBM when compared to cisplatin alone (Cis). Cis or Cis-PBM significantly decreased VEGF expression in cancer cells, while no changes were seen in the expression of TGF-β1 or EGF compared to control. ROS levels were similar in the Cis and Cis-PBM groups. Cells treated with Cis-PBM died by apoptosis, leading to greater consumption of ATP. These observations suggest that PBM may potentiate the effects of cisplatin, leading to increased drug cytotoxicity and enhanced cell death.

Decreased expression of mitochondrial miR-5787 contributes to chemoresistance by reprogramming glucose metabolism and inhibiting MT-CO3 translation

MicroRNAs (miRNAs) have been recently found in the mitochondria, and were named “mitomiRs”, but their function has remained elusive. Here, we aimed to assess the presence and function(s) of mitomiRs in tongue squamous cell carcinoma (TSCC).

Methods: miRNA microarray was performed in paired TSCC cell lines, Cal27 and its chemoresistant counterpart, Cal27-re. Decreased expression of mitomiRs in chemoresistant cells was characterized. The functions of mitomiRs were investigated by a series of in vitro and in vivo experiments.

Results: Differential microarray analysis identified downregulation of mitomiR-5787 in Cal27-re cells. We knocked down mitomiR-5787 in parental cells and upregulated its expression in cisplatin-resistant cells. The sensitivity of TSCC cells to cisplatin was regulated by miR-5787. The glucose metabolism assay suggested that reduced expression of miR-5787 changed the balance of glucose metabolism by shifting it from oxidative phosphorylation to aerobic glycolysis. Xenograft experiments in BALB/c-nu mice further verified the in vitro results. Reduced expression of miR-5787 contributes to chemoresistance in TSCC cells by inhibiting the translation of mitochondrial cytochrome c oxidase subunit 3 (MT-CO3). The prognostic analysis of 126 TSCC patients showed that the patients with low expression of miR-5787 and/or MT-CO3 had poor cisplatin sensitivity and prognosis.

Conclusions: Mitochondrial miR-5787 could regulate cisplatin resistance of TSCC cells and affect oxidative phosphorylation and aerobic glycolysis. Downregulation of miR-5787 inhibited the translation of MT-CO3 to regulate cisplatin resistance of TSCC. Mitochondrial miR-5787 and MT-CO3 can be used as predictive biomarkers or therapeutic targets for cisplatin chemotherapy resistance.

Long noncoding RNA ENST00000413528 sponges microRNA-593-5p to modulate human glioma growth via polo-like kinase 1

AIMS

In this study, we examined the expression of lncRNA ENST00000413528 in glioma and determined its role in glioma development.

METHODS

LncRNA ENST00000413528 was detected in glioma tissues by lncRNA microarray. Then, we performed real-time PCR, CCK-8, colony formation assay, flow cytometry, caspase-3/7 assay and animal experiment to detect the function of ENST00000413528 in glioma after ENST00000413528 knockdown. Subsequent bioinformatics analysis, luciferase reporter assays and RNA immunoprecipitation (RIP) assay western blotting indicated possible downstream regulatory molecules. The expression of PLK1 in glioma tissues was also examined by immunohistochemistry staining.

RESULTS

Expression of ENST00000413528 was significantly increased in glioma tissues and LN229 and U251 cells. PLK1 protein could not be detected in peritumoral brain edema (PTBE) tissues; however, it showed an increasing number of positively cytoplasmic stained from WHO-Grade II to Grade III gliomas. Knockdown of ENST00000413528 in glioma cells inhibited cell proliferation and colony formation abilities, induced the G0/G1 arrest of the cell cycle, and promoted apoptosis. The dual reporter assay and RNA immunoprecipitation assay verified the interaction between ENST00000413528 and miR-593. We also demonstrated that polo-like kinase 1 (PLK1) was regulated by miR-593; PLK1 messenger RNA lacking 3'UTR partially reversed the effects caused by ENST00000413528 knockdown or miR-593 upregulation.

CONCLUSION

lncRNA ENST00000413528 is closely related to the development of glioma via the miR-593-5p/PLK1 pathway.

Mitophagy in Cancer: A Tale of Adaptation

：In the past years, we have learnt that tumors co-evolve with their microenvironment, and that the active interaction between cancer cells and stromal cells plays a pivotal role in cancer initiation, progression and treatment response. Among the players involved, the pathways regulating mitochondrial functions have been shown to be crucial for both cancer and stromal cells. This is perhaps not surprising, considering that mitochondria in both cancerous and non-cancerous cells are decisive for vital metabolic and bioenergetic functions and to elicit cell death. The central part played by mitochondria also implies the existence of stringent mitochondrial quality control mechanisms, where a specialized autophagy pathway (mitophagy) ensures the selective removal of damaged or dysfunctional mitochondria. Although the molecular underpinnings of mitophagy regulation in mammalian cells remain incomplete, it is becoming clear that mitophagy pathways are intricately linked to the metabolic rewiring of cancer cells to support the high bioenergetic demand of the tumor. In this review, after a brief introduction of the main mitophagy regulators operating in mammalian cells, we discuss emerging cell autonomous roles of mitochondria quality control in cancer onset and progression. We also discuss the relevance of mitophagy in the cellular crosstalk with the tumor microenvironment and in anti-cancer therapy responses.

Inhibition of PI3K/mTOR increased the sensitivity of hepatocellular carcinoma cells to cisplatin via interference with mitochondrial-lysosomal crosstalk

OBJECTIVES

The genotoxicity of cisplatin towards nuclear DNA is not sufficient to explain the cisplatin resistance of hepatocellular carcinoma (HCC) cells; cisplatin interacts with many organelles, which can influence the sensitivity. Here, we explored the role of mitochondrial-lysosomal crosstalk in the cisplatin resistance of HCC cells.

MATERIALS AND METHODS

Huh7 and HepG2 cells were subjected to different treatments. Flow cytometry was conducted to detect mitochondrial reactive oxygen species, mitochondrial mass, lysosomal function, mitochondrial membrane potential and apoptosis. Western blotting was performed to evaluate protein levels. The oxygen consumption rate was measured to evaluate mitochondrial function.

RESULTS

Cisplatin activated mitophagy and lysosomal biogenesis, resulting in crosstalk between mitochondria and lysosomes and cisplatin resistance in HCC cells. Furthermore, a combination of cisplatin with the phosphatidylinositol-3-kinase/mammalian target of rapamycin (PI3K/mTOR) inhibitor PKI-402 induced lysosomal membrane permeabilization. This effect changed the role of the lysosome from a protective one to that of a cell death promoter, completely destroying the mitochondrial-lysosomal crosstalk and significantly enhancing the sensitivity of HCC cells to cisplatin.

CONCLUSIONS

This is the first evidence of the importance of mitochondrial-lysosomal crosstalk in the cisplatin resistance of HCC cells and of the destruction of this crosstalk by a PI3K/mTOR inhibitor to increase the sensitivity of HCC cells to cisplatin. This mechanism could be developed as a novel target for treatment of HCC in the future.

Circular RNA AKT3 upregulates PIK3R1 to enhance cisplatin resistance in gastric cancer via miR-198 suppression

BACKGROUND

Cisplatin (CDDP) treatment is one of the most predominant chemotherapeutic strategies for patients with gastric cancer (GC). A better understanding of the mechanisms of CDDP resistance can greatly improve therapeutic efficacy in patients with GC. Circular RNAs (circRNAs) are a class of noncoding RNAs whose functions are related to the pathogenesis of cancer, but, in CDDP resistance of GC remains unknown.

METHODS

circAKT3 (hsa_circ_0000199, a circRNA originating from exons 8, 9, 10, and 11 of the AKT3 gene) was identified by RNA sequencing and verified by quantitative reverse transcription PCR. The role of circAKT3 in CDDP resistance in GC was assessed both in vitro and in vivo. Luciferase reporter assay, biotin-coupled RNA pull-down and fluorescence in situ hybridization (FISH) were conducted to evaluate the interaction between circAKT3 and miR-198. Functional experiments were measured by western blotting, a cytotoxicity assay, clonogenic assay and flow cytometry.

RESULTS

The expression of circAKT3 was higher in CDDP-resistant GC tissues and cells than in CDDP-sensitive samples. The upregulation of circAKT3 in GC patients receiving CDDP therapy was significantly associated with aggressive characteristics and was an independent risk factor for disease-free survival (DFS). Our data indicated that circAKT3 promotes DNA damage repair and inhibits the apoptosis of GC cells in vivo and in vitro. Mechanistically, we verified that circAKT3 could promote PIK3R1 expression by sponging miR-198.

CONCLUSIONS

circAKT3 plays an important role in the resistance of GC to CDDP. Thus, our results highlight the potential of circAKT3 as a therapeutic target for GC patients receiving CDDP therapy.

Long Noncoding RNA MPRL Promotes Mitochondrial Fission and Cisplatin Chemosensitivity via Disruption of Pre-miRNA Processing

PURPOSE

The overall biological roles and clinical significance of most long noncoding RNAs (lncRNA) in chemosensitivity are not fully understood. We investigated the biological function, mechanism, and clinical significance of lncRNA NR_034085, which we termed miRNA processing-related lncRNA (MPRL), in tongue squamous cell carcinoma (TSCC).

EXPERIMENTAL DESIGN

LncRNA expression in TSCC cell lines with cisplatin treatment was measured by lncRNA microarray and confirmed in TSCC tissues. The functional roles of MPRL were demonstrated by a series of in vitro and in vivo experiments. The miRNA profiles, RNA pull-down, RNA immunoprecipitation, serial deletion analysis, and luciferase analyses were used to investigate the potential mechanisms of MPRL.

RESULTS

We found that MPRL expression was significantly upregulated in TSCC cell lines treated with cisplatin and transactivated by E2F1. MPRL controlled mitochondrial fission and cisplatin sensitivity through miR-483-5p. In exploring the underlying interaction between MPRL and miR-483-5p, we identified that cytoplasmic MPRL directly binds to pre-miR-483 within the loop region and blocks pre-miR-483 recognition and cleavage by TRBP-DICER-complex, thereby inhibiting miR-483-5p generation and upregulating miR-483-5p downstream target-FIS1 expression. Furthermore, overexpression or knockdown MPRL altered tumor apoptosis and growth in mouse xenografts. Importantly, we found that high expression of MPRL and pre-miR-483, and low expression of miR-483-5p were significantly associated with neoadjuvant chemosensitivity and better TSCC patients' prognosis.

CONCLUSIONS

We propose a model in which lncRNAs impair microprocessor recognition and are efficient of pre-miRNA cropping. In addition, our study reveals a novel regulatory network for mitochondrial fission and chemosensitivity and new biomarkers for prediction of neoadjuvant chemosensitivity in TSCC.These findings uncover a novel mechanism by which lncRNA determines mitochondrial fission and cisplatin chemosensitivity by inhibition of pre-miRNA processing and provide for the first time the rationale for lncRNA and miRNA biogenesis for predicting chemosensitivity and patient clinical prognosis.

Insights Into SND1 Oncogene Promoter Regulation

The staphylococcal nuclease and Tudor domain containing 1 gene (SND1), also known as Tudor-SN, TSN or p100, encodes an evolutionarily conserved protein with invariant domain composition. SND1 contains four repeated staphylococcal nuclease domains and a single Tudor domain, which confer it endonuclease activity and extraordinary capacity for interacting with nucleic acids, individual proteins and protein complexes. Originally described as a transcriptional coactivator, SND1 plays fundamental roles in the regulation of gene expression, including RNA splicing, interference, stability, and editing, as well as in the regulation of protein and lipid homeostasis. Recently, SND1 has gained attention as a potential disease biomarker due to its positive correlation with cancer progression and metastatic spread. Such functional diversity of SND1 marks this gene as interesting for further analysis in relation with the multiple levels of regulation of SND1 protein production. In this review, we summarize the SND1 genomic region and promoter architecture, the set of transcription factors that can bind the proximal promoter, and the evidence supporting transactivation of SND1 promoter by a number of signal transduction pathways operating in different cell types and conditions. Unraveling the mechanisms responsible for SND1 promoter regulation is of utmost interest to decipher the SND1 contribution in the realm of both normal and abnormal physiology.

Macrophage migration inhibitory factor regulates mitochondrial dynamics and cell growth of human cancer cell lines through CD74-NF-κB signaling

The indispensable role of macrophage migration inhibitory factor (MIF) in cancer cell proliferation is unambiguous, although which specific roles the cytokine plays to block apoptosis by preserving cell growth is still obscure. Using different cancer cell lines (AGS, HepG2, HCT116, and HeLa), here we report that the silencing of MIF severely deregulated mitochondrial structural dynamics by shifting the balance toward excess fission, besides inducing apoptosis with increasing sub-G₀ cells. Furthermore, enhanced mitochondrial Bax translocation along with cytochrome c release, down-regulation of Bcl-xL, and Bcl-2 as well as up-regulation of Bad, Bax, and p53 indicated the activation of a mitochondrial pathway of apoptosis upon MIF silencing. The data also indicate a concerted down-regulation of Opa1 and Mfn1 along with a significant elevation of Drp1, cumulatively causing mitochondrial fragmentation upon MIF silencing. Up-regulation of Drp1 was found to be further coupled with fissogenic serine 616 phosphorylation and serine 637 dephosphorylation, thus ensuring enhanced mitochondrial translocation. Interestingly, MIF silencing was found to be associated with decreased NF-κB activation. In fact, NF-κB knockdown in turn increased mitochondrial fission and cell death. In addition, the silencing of CD74, the cognate receptor of MIF, remarkably increased mitochondrial fragmentation in addition to preventing cell proliferation, inducing mitochondrial depolarization, and increasing apoptotic cell death. This indicates the active operation of a MIF-regulated CD74-NF-κB signaling axis for maintaining mitochondrial stability and cell growth. Thus, we propose that MIF, through CD74, constitutively activates NF-κB to control mitochondrial dynamics and stability for promoting carcinogenesis via averting apoptosis.

Tumour microenvironment on mitochondrial dynamics and chemoresistance in cancer

Mitochondria, evolutionally acquired symbionts of eukaryotic cells, are essential cytoplasmic organelles. They are structurally dynamic organelles that continually go through fission and fusion processes in response to various stimuli. Tumour tissue is composed of not just cancer cells but also various cell types like fibroblasts, mesenchymal stem and immune cells. Mitochondrial dynamics of cancer cells has been shown to be significantly affected by features of tumour microenvironment such as hypoxia, inflammation and energy deprivation. The interactions of cancer cells with tumour microenvironment like hypoxia give rise to the inter- and intratumoural heterogeneity, causing chemoresistance. In this review, we will focus on the chemoresistance by tumoural heterogeneity in relation to mitochondrial dynamics of cancer cells. Recent findings in molecular mechanisms involved in the control of mitochondrial dynamics as well as the impact of mitochondrial dynamics on drug sensitivity in cancer are highlighted in the current review.

microRNA-200a-3p enhances mitochondrial elongation by targeting mitochondrial fission factor

Mitochondria play pivotal roles in the ATP production, apoptosis and generation of reactive oxygen species. Although dynamic regulation of mitochondria morphology is a critical step to maintain cellular homeostasis, the regulatory mechanisms are not yet fully elucidated. In this study, we identified miR-200a-3p as a novel regulator of mitochondrial dynamics by targeting mitochondrial fission factor (MFF). We demonstrated that the ectopic expression of miR-200a-3p enhanced mitochondrial elongation, mitochondrial ATP synthesis, mitochondrial membrane potential and oxygen consumption rate. These results indicate that miR-200a-3p positively regulates mitochondrial elongation by downregulating MFF expression.

SUOX is negatively associated with multistep carcinogenesis and proliferation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the head and neck region. The aim of this study was to identify the key molecules and to elucidate the molecular mechanisms of OSCC carcinogenesis through a microarray analysis of RNA extracted from normal epithelium, dysplasia, and squamous cell carcinoma components. Out of molecules that showed changes in gene expression in the microarray analysis, we focused on Sulfite oxidase (SUOX), which correlated significantly with carcinogenic process and exhibited a stepwise decrease in expression. The expression of SUOX was evaluated in detail at the protein level using samples from 58 patients with cancer of the tongue, and correlating clinicopathological factors were also comprehensively examined. SUOX expression declined significantly from normal epithelium to dysplasia to squamous cell carcinoma components in line with carcinogenic process. With regard to squamous cell carcinoma, SUOX expression was significantly lower when T classification was high. Our findings indicated that SUOX is negatively associated with the progression and proliferation of tongue cancer, and suggest that SUOX may be a key molecule in tongue tumors.

TR4 nuclear receptor enhances the cisplatin chemo-sensitivity via altering the ATF3 expression to better suppress HCC cell growth

Early studies indicated that TR4 nuclear receptor (TR4) may play a key role to modulate the prostate cancer progression, its potential linkage to liver cancer progression, however, remains unclear. Here we found that higher TR4 expression in hepatocellular carcinoma (HCC) cells might enhance the efficacy of cisplatin chemotherapy to better suppress the HCC progression. Knocking down TR4 with TR4-siRNA in HCC Huh7 and Hep3B cells increased cisplatin chemotherapy resistance and overexpression of TR4 with TR4-cDNA in HCC LM3 and SNU387 cells increased cisplatin chemotherapy sensitivity. Mechanism dissection found that TR4 might function through altering the ATF3 expression at the transcriptional level to enhance the cisplatin chemotherapy sensitivity, and interrupting ATF3 expression via ATF3-siRNA reversed TR4-enhanced cisplatin chemotherapy sensitivity in HCC cells. The in vivo HCC mouse model using xenografted HCC LM3 cells also confirmed in vitro cell lines data showing TR4 enhanced the cisplatin chemotherapy sensitivity. Together, these results provided a new potential therapeutic approach via altering the TR4-ATF3 signals to increase the efficacy of cisplatin to better suppress the HCC progression.

SOX8 regulates cancer stem-like properties and cisplatin-induced EMT in tongue squamous cell carcinoma by acting on the Wnt/β-catenin pathway

A sub-population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin-resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin-resistant TSCC cells, which displayed CSC-like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin-resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β-catenin pathway mediated the cancer stem-like properties in cisplatin-resistant TSCC cells. Further studies showed that the transfection of active β-catenin in SOX8 stable-knockdown cells partly rescued the SOX8 silencing-induced repression of stem-like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled-7 (FZD7) and induced the FZD7-mediated activation of the Wnt/β-catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7-mediated Wnt/β-catenin pathway.

Altered Mitochondrial Signalling and Metabolism in Cancer

Mitochondria being the central organelle for metabolism and other cell signalling pathways have remained the topic of interest to tumour biologists. In spite of the wide acceptance of Warburg’s hypothesis, role of mitochondrial metabolism in cancer is still unclear. Uncontrolled growth and proliferation, hallmarks of tumour cells, are maintained when the cells adapt to metabolic reprogramming with the help of altered metabolism of mitochondria. This review has focussed on different aspects of mitochondrial metabolism and inter-related signalling pathways which have been found to be modified in cancer.

MicroRNA-593-3p regulates insulin-promoted glucose consumption by targeting Slc38a1 and CLIP3

Insulin plays an important role in the regulation of glucose metabolism. However, the molecular mechanisms involved are not entirely clarified. In this context, we found that miR-593-3p negatively regulates insulin-regulated glucose metabolism in hepatocellular carcinoma HepG2 and Bel7402 cells. We then identified Slc38a1 and CLIP3 as novel targets of miR-593-3p. Further studies demonstrated that Slc38a1 and CLIP3 mediate insulin-regulated glucose metabolism. Interestingly, we also demonstrated that miR-593-3p expression was negatively associated with Slc38a1 and CLIP3 expression in insulin-treated HepG2 cells, and insulin-induced Slc38a1 and CLIP3 expression via downregulation of miR-593-3p. Taken together, this study indicates that inhibition of miRNA-593-3p by insulin promotes glucose metabolism through the regulation of Slc38a1 and CLIP3 expression, and provides a new insight into the role and mechanism of insulin-induced glycolysis.

Effect of the BRCA1-SIRT1-EGFR axis on cisplatin sensitivity in ovarian cancer

There is accumulating evidence that breast cancer 1 (BRCA1), sirtuin 1 (SIRT1), and epidermal growth factor receptor (EGFR) help to modulate cisplatin cytotoxicity. The role of dynamic crosstalk among BRCA1, SIRT1, and EGFR in cisplatin sensitivity remains largely unknown. We found that BRCA1, SIRT1, and EGFR levels were increased in cisplatin-resistant ovarian cancers compared with those in cisplatin-sensitive ovarian cancers. Hypomethylation in the BRCA1 promoter was associated with BRCA1 activation, significantly elevated SIRT1 levels, decreased nicotinamide adenine dinucleotide (NAD)-mediated SIRT1 activity, and decreased EGFR levels. Treatment with 5 and 10 μg/ml cisplatin induced a gradual increase in BRCA1 and SIRT1 levels and a gradual decrease in NAD levels and NAD-mediated SIRT1 activity, whereas EGFR levels were increased or decreased by treatment with 5 or 10 μg/ml cisplatin, respectively. The overexpression of SIRT1 or the enhancement of SIRT1 activity synergistically enhanced the BRCA1-mediated effects on EGFR transcription. In contrast, the knockdown of SIRT1 or the inhibition of SIRT1 activity inhibited the BRCA1-mediated effects on EGFR transcription. BRCA1 regulates EGFR through a BRCA1-mediated balance between SIRT1 expression and activity. Those results improve our understanding of the basic molecular mechanism underlying BRCA1-related cisplatin resistance in ovarian cancer.