BREAKING! Study Discovers SARS-CoV-2 Could Be Carcinogenic As It Causes Mutagenesis, Telomere Dysregulation And Impairs DNA Mismatch Repair!
More worrisome data has emerged from a new study led by researchers from the University of Vermont, Sidney Kimmel Medical College and the University of Vermont Medical Center that indicates more possible long-term medical conditions arising in Long COVID including various cancers! The study that also involved medical scientists from Duke University, New York University and Icahn School of Medicine at Mount Sinai found that the SARS-CoV-2 coronavirus is capable of hijacking the host DNA, causing mutagenesis, telomere dysregulation and it also impairs DNA mismatch repair, giving rise to the state of hypermutability!
Thailand Medical News
has been warning about the long-term rise of various accelerated and aggressive cancers as a result of SARS-CoV-2 infections since the beginning of the pandemic. (simply search cancer in the site’s search function)
The various arising conditions of Long COVID is ever on the increase but the molecular underpinnings at the cellular level are poorly defined.
The study team alarmingly found that SARS-CoV-2 infection triggers host cell genome instability by modulating the expression of molecules of DNA repair and mutagenic translesion synthesis. (Translesion DNA synthesis (TLS) is the process by which cells copy DNA containing unrepaired damage that blocks progression of the replication fork.)
The study findings further showed that SARS-CoV-2 infection causes genetic alterations, such as increased mutagenesis, telomere dysregulation, and elevated microsatellite instability (MSI).
Microsatellite instability (MSI) is the condition of genetic hypermutability (predisposition to mutation) that results from impaired DNA mismatch repair (MMR). The presence of MSI represents phenotypic evidence that MMR is not functioning normally.
The MSI phenotype was coupled to reduce the genes that are critical for DNA repair such as MLH1, MSH6, and MSH2 in infected cells.
Interestingly, pre-treatment of cells with the REV1-targeting translesion DNA synthesis inhibitor, JH-RE-06, suppresses SARS-CoV-2 proliferation and dramatically represses the SARS-CoV-2-dependent genome instability.
It was found that mechanistically, JH-RE-06 treatment induces autophagy, which the study team hypothesizes limits SARS-CoV-2 proliferation and, therefore, the hijacking of host-cell genome instability pathways. These results have implications for understanding the pathobiological consequences of COVID-19.
The study findings were published on a preprint server: Research Square and are currently being peer reviewed. https://www.researchsquare.com/article/rs-1556634/v1
To date, it has been found that between 40 to 70 percent of ‘recovered’ COVID-19 patients are susceptible to developing long-COVID, where general malaise and debilitating symptoms persist. Considering that official data shows that about 505 million people globally have been affected by the SARS-CoV-2 virus while in reality the actual figure could be 4- to 5-fold, the future shows a high burden on the public healthcare infrastructure and increased excess mortality rates!
News studies also indicate that cardiovascular health and
brain structure are negatively impacted in patients irrespective of the symptom severity during active SARS-CoV-2 infection.
Shockingly, other studies indicate senescence-associated phenotypes and enrichment of aging signatures in infected cells and tissues, suggesting large-scale uncharacterized cellular damage from SARS-CoV-2. https://www.medrxiv.org/content/10.1101/2021.11.24.21266779v1
Hence, a detailed molecular understanding of the SARS-CoV-2-dependent host-cell pathophysiology will aid in addressing and managing the COVID-19 disease course.
The same study team previously reported that SARS-CoV-2 infection triggers an ATR (ataxia telangiectasia and Rad3-related protein) DNA damage response (DDR) in Vero-E6 cells. https://pubmed.ncbi.nlm.nih.gov/34600299/
The activated DDR serves as a molecular link to engage different DNA repair pathways or evoke translesion synthesis (TLS) to bypass irreparable damage. An engaged TLS pathway not only propels DNA mutagenesis but also regulates metabolic processes. Dysregulation of these pathways causes genome instability, which can be phenotypically quantified as differential expression of molecules of these pathways and different genetic alterations at the DNA.
In order to whether SARS-CoV-2 triggers genome instability, the study team first quantified relative transcript levels of the DDR, DNA repair, and TLS genes at 48 hours post-infection in A549-ACE2 + cells.
The study team found upregulation of the DDR genes (ATM, ATR, including CHK1), in addition to the increased expression of specied DNA repair genes from double-strand break repair (DSBR: BRCA1, MRE11A, PARP1, and RAD51),nucleotide excision repair (NER: XPA), and the major mutagenic TLS genes (POLh, POLk, POLi, REV1, and REV7). Similarly, ATR expression was detected in the lung tissue of the Golden Syrian hamster at 30 days post-SARS-CoV-2 infection. At the protein level, each factor exhibited a unique pattern of upregulation with the peak expression levels between 4 to 8 hours post-infection.
Such a unique expression pattern was not observed in influenza A virus-infected A549-ACE2 + cells where a different set of DDR genes (DDB2, DDB1, DDIT4, SMC5, etc.) were upregulated.
Subsequent immunohistochemical analysis of the human autopsy COVID-19 lung tissues showed an increased expression of gH2AX compared to their PMI (post-mortem interval)-matched controls, just as was observed in lung tissue of Golden Syrian hamster up to 30 days post-SARS-CoV-2 infection.
Interestingly, 53BP1, an important transducer of DNA damage and genome instability, was highly expressed in the terminal bronchioles, but the overall expression in the surrounding lung tissue was less pronounced. Within a limited group of patients investigated at least three months following acute COVID, longitudinal expression of 53BP1 at three intervals six months apart following the first visit showed a significant decrease in expression in three of the five patients. These results suggest SARS-CoV-2 infection modulates the expression of genome instability markers in cells, autopsy lung tissues, Golden Syrian hamster lung tissue, and sera from post-COVID patients.
The study team next assessed telomere dysfunction, an important genome instability marker, by quantifying telomere length and expression of key telomere maintenance proteins.
The study findings showed significant telomere instability ie marked by a reduction and lengthening of telomeres in autopsy patient lung tissues, infected A549-ACE2 + cells, and lung tissue of Golden Syrian hamster for 30 days post-SARS-CoV-2 infection.
Also, expression of the two shelterin proteins, TRF2 and POT1, which encapsulate telomeres into protective units, was significantly repressed in autopsy lung tissues and infected cells, in contrast to the elevated hTERT expression in infected A549-ACE2 + cells and the lung tissue of Golden Syrian hamster 30 days post-SARS-CoV-2 infection. Because different cell lines exhibited distinct telomere lengths, SARS-CoV-2 may be impacting the telomere biology uniquely in different tissues.
As it was found that SARS-CoV-2 increases the expression of mutagenic TLS polymerases, the study team next tested a two-fold hypothesis:
-First, whether SARS-CoV-2-dependent increased TLS expression inadvertently causes host cell genetic alterations
-Secondly, whether inhibiting the TLS pathway diminishes the deleterious consequences of SARS-CoV-2 infection.
The findings showed a 120% increase in mutation frequency at the HPRT (hypoxanthine phosphoribosyl transferase) gene, suggesting a general increase in the mutational burden in infected cells. Likewise, other mutability events, such as microsatellite instability (MSI), where insertions or deletions occur at a high frequency at repetitive DNA, were high not only inA549-ACE2 + infected cells but also in most of the autopsy lung tissues compared to the PMI-matched controls.
Also observed was a significant reduction inexpression of the mismatch repair (MMR) proteins, MSH2, MLH1 and MSH6 in A549-ACE2 + cells infected with SARS-CoV-2.
In order to determine MMR status in patients post-COVID, the study team tested the longitudinal expression of MSH2 protein in patient sera and found it to be significantly reduced in two of the five tested patients.
Elevated MSI and deficient MMR (dMMR) are a hallmark of certain cancers; whether long-COVID patients with the said changes would be at risk for cancer needs further longitudinal analysis
In order to determine whether TLS inhibition might suppress the noted mutagenic events, the study team tested whether TLS inhibitor, JH-RE-06, that specifically targets the REV7 interface of REV1 TLS polymerase suppresses genetic alterations in host cell DNA.
It was found that JH-RE-06 treatment suppresses both theSARS-CoV-2-dependent HPRT mutagenesis and MSI in infected A549-ACE2 + cells, suggesting that increased expression of TLS polymerases indeed contributes to the elevation of mutagenic events and that therapeutic inhibition of TLS can suppress SARS-CoV-2-dependent deleterious consequences.
The study team encouraged by this result, tested whether other genome instability markers were also repressed by the JH-RE-06 treatment in SARS-CoV-2 infected cells.
It was found that JH-RE-06 treatment of the A549-ACE2 + cells suppressed transcript expression of all the DDR, TLS, and DNA repair genes. Likewise, the enhanced expression of gH2AX in SARS-CoV-2 infected A549-ACE2 + cells at 48 hours was suppressed by up to 40-fold post-JH-RE-06 treatment.
Importantly, JH-RE-06 treatment did not rescue telomere instability in SARS-CoV-2 infected A549-ACE2 + cells, suggesting that SARS-CoV-2 may impact telomere instability by an independent pathway
The study team unexpectedly observed that the compound JH-RE-06 was also able to directly suppress the proliferation of SARS-CoV-2 in three independent cell lines ie Vero, A549-ACE2+, and Calu-3 cells as noted by the relative N content in cells.
This surprising result of JH-RE-06-dependent suppression of SARS-CoV-2 proliferation was also observed in the STAT1KO cell line, suggesting independence from the immune pathway and a possible role of REV1 in SARS-CoV-2propagation. Because siREV1 knockdown in A549-ACE2 + cells also suppressed SARS-CoV-2 propagation, the study team concluded that REV1 has a specific role in virus propagation in cells.
Since REV1 inhibition was recently shown to trigger autophagy, the study team tested whether JH-RE-06 treatment induces autophagy to limit SARS-CoV-2. On its own, SARS-CoV-2 infection steadily increases LC3 expression over time, without an increase in p62. However, JH-RE-06 treatment significantly increases the expression of p62 and LC3 in SARS-CoV-2 infected cells, indicating that JH-RE-06 treatment upregulates p62 expression that might promote lysosomal degradation of SARS-CoV-2, limiting its propagation in cells. Further studies are needed to delineate the exact mechanism by which JH-RE-06-dependent autophagy suppresses SARS-CoV-2 proliferation.
The study team next reexamined existing RNA sequence data because REV1’s engagement with viruses, particularlySARS-CoV-2, was unknown.
It was unexpectedly observed a gene enrichment for viral myocarditis in the REV1KO mouse embryonic broblasts (KEGG pathway mmu05416 from which prompted the team to test whether JH-RE-06 treatment might suppress one of the key factors, CASP9, involved in SARS-CoV-2-dependent increase in myocarditis.
It was found that treatment of cells with the JH-RE-06 inhibitor suppresses CASP9 expression, suggesting mechanisms of genome instability might associate with myocarditis with therapeutic implications during long-COVID.
Although genome instability is considered a hallmark of some cancers and can be associated with other human diseases, large-scale and long-term human studies are required to establish whether SARS-CoV-2infection will be a risk factor for developing these diseases.
Already RNA-viruses such as HTLV-1and HCV are known to promote oncogenesis and typically manifest over several years and rely on host genetic variability and environmental factors to develop cancer. https://pubmed.ncbi.nlm.nih.gov/24629334/
The study team admitted certain study limitations ie: 1) the sample size for the clinical post-COVID specimens were low, 2) the follow-up period for the post-COVID patients is short when considering the time frame for carcinogenesis, and 3) the mechanisms of dMMR are unknown at the molecular. Additionally, within the hamster animal model, at 60 days post-infection, when Nucleocapsid (N) expression dissipates, some genome instability markers, gH2AX, ATR, TERT, and telomere length alterations, return to baseline levels. However, their characterization in long-COVID patients remains.
The study findings collectively show that SARS-CoV-2 infection triggers genome instability quantified as modulated expression of various biomarkers (DDR, DNA repair, and TLS), telomere instability, and enhanced host cell mutagenesis in cultured cells, hamster model, and post-COVID patients.
It should be noted that already physicians around the world are reporting the increase of various cancers over the last few months including gastrointestinal cancers, liver cancers, lung cancers etc.
Thailand Medical News
would also like to add that there are many phytochemicals that can act as a REV1-targeting translesion DNA synthesis inhibitor and some can also help repairing viral based DNA damage. (we will be covering these in a soon to be launched private platform.)
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