The interaction between mitochondria and oncoviruses

The Eradication of Carcinogenic Viruses in Established Solid Cancers

Carcinogenic viruses (oncoviruses) can initiate cancer, but their impact on established cancer varies. Some of these viruses prolong survival while others shorten it. This study classifies oncoviruses into two categories: viruses which induce a strong CD8+T cell reaction in non-cancerous tissues, and viruses which induce a weak CD8+ T cell reaction in non-cancerous tissues. The classification proves useful in predicting the effect of oncoviruses on the prognosis of solid cancers. Therefore, while eliminating carcinogenic viruses in healthy individuals (for example by immunization) may be important for cancer prevention, this study suggests that only viruses which induce a weak CD8+ T cell reaction should be eradicated in established solid tumors. The model correctly predicts the effect of oncoviruses on survival for six out of seven known oncoviruses, indicating that immune modulation by oncoviruses has a prominent effect on prognosis. It seems that CD8+ T cell response to oncoviruses observed in infected benign tissues is retained in infected tumors. Clinical significance: the effect of oncoviruses on solid cancer prognosis can be predicted with confidence based on immunological responses when clinical data are unavailable.

Mitochondrial DNA content as a biomarker for oral carcinogenesis: correlation with clinicopathologic parameters

BACKGROUND

Mitochondrial genome (mtDNA) exhibits greater vulnerability to mutations and/or copy number variations than nuclear counterpart (nDNA) in both normal and cancer cells due to oxidative stress generated by inflammation, viral infections, physical, mechanical, and chemical load. The study was designed to evaluate the mtDNA content in oral potentially malignant disorders (OPMDs) and oral squamous cell carcinoma (OSCC). Various parameters were analyzed including its variation with human papillomavirus (HPV) during oral carcinogenesis.

METHODS

The present cross-sectional study comprised of two hundred patients (100 OPMDs and 100 OSCCs) and 100 healthy controls. PCR amplifications were done for mtDNA content and HPV in OPMDs and OSCC using real-time and conventional PCR respectively.

RESULTS

The relative mtDNA content was assessed quantitatively and it was observed that mtDNA was greater in OSCC (7.60±0.94) followed by OPMDs (5.93±0.92) and controls (5.37±0.95). It showed a positive linear correlation with habits and increasing histopathological grades. Total HPV-positive study groups showed higher mtDNA content (7.06±1.64) than HPV-negative counterparts (6.21±1.29).

CONCLUSIONS

An elevated mutant mtDNA may be attributed to increased free radicals and selective cell clonal proliferation in test groups. Moreover, sustained HPV infection enhances tumorigenesis through mitochondria mediated apoptosis. Since, mtDNA content is directly linked to oxidative DNA damage, these quantifications might serve as a surrogate measure for invasiveness in dysplastic lesions and typify their malignant potential.

Mitochondrial DNA is a target of HBV integration

Hepatitis B virus (HBV) may integrate into the genome of infected cells and contribute to hepatocarcinogenesis. However, the role of HBV integration in hepatocellular carcinoma (HCC) development remains unclear. In this study, we apply a high-throughput HBV integration sequencing approach that allows sensitive identification of HBV integration sites and enumeration of integration clones. We identify 3339 HBV integration sites in paired tumour and non-tumour tissue samples from 7 patients with HCC. We detect 2107 clonally expanded integrations (1817 in tumour and 290 in non-tumour tissues), and a significant enrichment of clonal HBV integrations in mitochondrial DNA (mtDNA) preferentially occurring in the oxidative phosphorylation genes (OXPHOS) and D-loop region. We also find that HBV RNA sequences are imported into the mitochondria of hepatoma cells with the involvement of polynucleotide phosphorylase (PNPASE), and that HBV RNA might have a role in the process of HBV integration into mtDNA. Our results suggest a potential mechanism by which HBV integration may contribute to HCC development.

Switchable hepatic organelles aberrations in DEN-induced mice under the influence of chemically characterized silk sericin

OBJECTIVE

Assessing the beneficial effects of silk sericin against hepatic injury induced by diethylnitrosamine (DEN).

METHODS

Aiming at promoting sericin as a natural product able to counteract the hazards of toxic elements, HPLC profile was conducted on the extracted sericin sample versus the standard one to qualitatively identify it. Following sericin treatment on human HepG2 liver cancer cells, many parameters were analyzed in vitro including cell viability, cell cycle, and cell apoptosis. Hepatic pro-inflammatory cytokines as well as histopathological and ultrastructure changes were evaluated in vivo in the different experimental groups.

RESULTS

Sericin exhibited a dose-dependent cytotoxic effect on HepG2 cells with an IC50 of 14.12 + 0.75 μg/mL. The hepatotoxicity of DEN was manifested in mice by increased pro-inflammatory markers (IL-2, IL-6, and TNF-α), decreased IL-10, liver structure deterioration, and characteristic histopathological and ultrastructure changes. Sericin administration reversed most of the observed alterations inflected by DEN.

CONCLUSIONS

Our results substantiate the sericin's powerful apoptotic impact in vitro. In experimental mice, combination treatment using sericin together with melatonin appears to be more potent in mitigating the adverse effects of DEN. However, further investigations are needed to identify the underlying mechanism of action and complement the knowledge about the expected medicinal values of sericin.

Mitochondrial Dysfunction and Chronic Liver Disease

Mitochondria are generally considered the powerhouse of the cell, a small subcellular organelle that produces most of the cellular energy in the form of adenosine triphosphate (ATP). In addition, mitochondria are involved in various biological functions, such as biosynthesis, lipid metabolism, oxidative phosphorylation, cell signal transduction, and apoptosis. Mitochondrial dysfunction is manifested in different aspects, like increased mitochondrial reactive oxygen species (ROS), mitochondrial DNA (mtDNA) damage, adenosine triphosphate (ATP) synthesis disorder, abnormal mitophagy, as well as changes in mitochondrial morphology and structure. Mitochondrial dysfunction is related to the occurrence and development of various chronic liver diseases, including hepatocellular carcinoma (HCC), viral hepatitis, drug-induced liver injury (DILI), alcoholic fatty liver (AFL), and non-alcoholic fatty liver (NAFL). In this review, we summarize and discuss the role and mechanisms of mitochondrial dysfunction in chronic liver disease, focusing on and discussing some of the latest studies on mitochondria and chronic liver disease.

MicroRNAs Encoded by Virus and Small RNAs Encoded by Bacteria Associated with Oncogenic Processes

Cancer is a deadly disease and, globally, represents the second leading cause of death in the world. Although it is a disease where several factors can help its development, virus induced infections have been associated with different types of neoplasms. However, in bacterial infections, their participation is not known for certain. Among the proposed approaches to oncogenesis risks in different infections are microRNAs (miRNAs). These are small molecules composed of RNA with a length of 22 nucleotides capable of regulating gene expression by directing protein complexes that suppress the untranslated region of mRNA. These miRNAs and other recently described, such as small RNAs (sRNAs), are deregulated in the development of cancer, becoming promising biomarkers. Thus, resulting in a study possibility, searching for new tools with diagnostic and therapeutic approaches to multiple oncological diseases, as miRNAs and sRNAs are main players of gene expression and host–infectious agent interaction. Moreover, sRNAs with limited complementarity are similar to eukaryotic miRNAs in their ability to modulate the activity and stability of multiple mRNAs. Here, we will describe the regulatory RNAs from viruses that have been associated with cancer and how sRNAs in bacteria can be related to this disease.

Antiviral Responses in Cancer: Boosting Antitumor Immunity Through Activation of Interferon Pathway in the Tumor Microenvironment

In recent years, it became apparent that cancers either associated with viral infections or aberrantly expressing endogenous retroviral elements (EREs) are more immunogenic, exhibiting an intense intra-tumor immune cell infiltration characterized by a robust cytolytic apparatus. On the other hand, epigenetic regulation of EREs is crucial to maintain steady-state conditions and cell homeostasis. In line with this, epigenetic disruptions within steady-state cells can lead to cancer development and trigger the release of EREs into the cytoplasmic compartment. As such, detection of viral molecules by intracellular innate immune sensors leads to the production of type I and type III interferons that act to induce an antiviral state, thus restraining viral replication. This knowledge has recently gained momentum due to the possibility of triggering intratumoral activation of interferon responses, which could be used as an adjuvant to elicit strong anti-tumor immune responses that ultimately lead to a cascade of cytokine production. Accordingly, several therapeutic approaches are currently being tested using this rationale to improve responses to cancer immunotherapies. In this review, we discuss the immune mechanisms operating in viral infections, show evidence that exogenous viruses and endogenous retroviruses in cancer may enhance tumor immunogenicity, dissect the epigenetic control of EREs, and point to interferon pathway activation in the tumor milieu as a promising molecular predictive marker and immunotherapy target. Finally, we briefly discuss current strategies to modulate these responses within tumor tissues, including the clinical use of innate immune receptor agonists and DNA demethylating agents.

Mitochondria and Mitochondrial DNA: Key Elements in the Pathogenesis and Exacerbation of the Inflammatory State Caused by COVID-19

Background and Objectives. The importance of mitochondria in inflammatory pathologies, besides providing energy, is associated with the release of mitochondrial damage products, such as mitochondrial DNA (mt-DNA), which may perpetuate inflammation. In this review, we aimed to show the importance of mitochondria, as organelles that produce energy and intervene in multiple pathologies, focusing mainly in COVID-19 and using multiple molecular mechanisms that allow for the replication and maintenance of the viral genome, leading to the exacerbation and spread of the inflammatory response. The evidence suggests that mitochondria are implicated in the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which forms double-membrane vesicles and evades detection by the cell defense system. These mitochondrion-hijacking vesicles damage the integrity of the mitochondrion’s membrane, releasing mt-DNA into circulation and triggering the activation of innate immunity, which may contribute to an exacerbation of the pro-inflammatory state. Conclusions. While mitochondrial dysfunction in COVID-19 continues to be studied, the use of mt-DNA as an indicator of prognosis and severity is a potential area yet to be explored.

Cannabinoid-Induced Immunomodulation during Viral Infections: A Focus on Mitochondria

This review examines the impact of cannabinoids on viral infections, as well as its effects on the mitochondria of the nervous and immune system. The paper conveys information about the beneficial and negative impacts of cannabinoids on viral infections, especially HIV-1. These include effects on the inflammatory response as well as neuroprotective effects. We also explore non-apoptotic mitochondrial pathways modulated by the activity of cannabinoids, resulting in modifications to cellular functions. As a large part of the literature derives from studies of the nervous system, we first compile the information related to mitochondrial functions in this system, particularly through the CB1 receptor. Finally, we reflect on how this knowledge could complement what has been demonstrated in the immune system, especially in the context of the CB2 receptor and Ca²⁺ uptake. The overall conclusion of the review is that cannabinoids have the potential to affect a broad range of cell types through mitochondrial modulation, be it through receptor-specific action or not, and that this pathway has a potential implication in cases of viral infection.