Biology subjects

Chadha, S.

Publications and source records attributed to Chadha, S..

5 recordsLinked to original sources

bioRxiv2024

The membrane-associated ubiquitin ligase MARCHF8 promotes cancer immune evasion by degrading MHC class I proteins

The loss of major histocompatibility complex class I (MHC-I) molecules has been proposed as a mechanism by which cancer cells evade tumor-specific T cells in immune checkpoint inhibitor (ICI)-refractory patients. Nevertheless, the mechanism by which cancer cells downregulate MHC-I is poorly understood. We report here that membrane-associated RING-CH-type finger 8 (MARCHF8), upregulated by human papillomavirus (HPV), ubiquitinates and degrades MHC-I proteins in HPV-positive head and neck cancer (HPV+ HNC). MARCHF8 knockdown restores MHC-I levels on HPV+ HNC cells. We further reveal that Marchf8 knockout significantly suppresses tumor growth and increases the infiltration of natural killer (NK) and T cells in the tumor microenvironment (TME). Furthermore, Marchf8 knockout markedly increases crosstalk between the cytotoxic NK cells and CD8+ T cells with macrophages and enhances the tumor cell-killing activity of CD8+ T cells. CD8+ T cell depletion in mice abrogates Marchf8 knockout-driven tumor suppression and T cell infiltration. Interestingly, Marchf8 knockout, in combination with anti-PD-1 treatment, synergistically suppresses tumor growth in mice bearing ICI-refractory tumors. Taken together, our finding suggests that MARCHF8 could be a promising target for novel immunotherapy for HPV+ HNC patients. One Sentence SummaryTargeting MARCHF8 restores MHC-I proteins, induces antitumor CD8+ T cell activity, and suppresses the growth of ICI-refractory tumors.

cancer biology↗

bioRxiv2023

Novel DNA methylation changes in mouse lungs associated with heavy smoking

Smoking is a potent cause of asthma, chronic obstructive pulmonary disease (COPD) and many other health defects, and changes in DNA methylation (DNAm) have been identified as a potential link between smoking and these health outcomes. However, most links between smoking and DNAm have been made using blood and other easily accessible tissues in humans, while evidence from more directly affected tissues such as the lungs is greatly lacking. Here, we identified DNAm patterns which are altered by smoking directly in the lungs. We used a well-established mouse model to measure the effects of heavy smoking first on lung phenotype immediately after smoking and then after a period of smoking cessation. Next, we determined whether our mouse model could recapitulate previous DNAm patterns observed in smoking humans by measuring DNAm at a candidate gene responsive to cigarette smoke (CS), Cyp1a1. Finally we carried out epigenome-wide DNAm analyses using the newly released Illumina mouse methylation microarrays. Our results recapitulate some of the phenotypes and DNAm patterns observed in human studies but reveal 32 differentially methylated genes specific to the lungs which have not been previously associated with smoking. The affected genes are known to be involved in nicotine dependency, tumorigenesis and metastasis, immune cell dysfunction, lung function decline, and COPD. This research emphasizes the need to study CS-mediated DNAm signatures in directly affected tissues like the lungs, as that may be essential in understanding mechanisms underlying CS-mediated health outcomes.

molecular biology↗

bioRxiv2023

The membrane-associated ubiquitin ligase MARCHF8 stabilizes the human papillomavirus oncoprotein E7 by degrading CUL1 and UBE2L3 in head and neck cancer

The human papillomavirus (HPV) oncoprotein E7 is a relatively short-lived protein required for HPV-driven cancer development and maintenance. E7 is degraded through ubiquitination mediated by cullin 1 (CUL1) and the ubiquitin-conjugating enzyme E2 L3 (UBE2L3). However, E7 proteins are maintained at high levels in most HPV-positive cancer cells. A previous proteomics study has shown that UBE2L3 and CUL1 protein levels are increased by the knockdown of the E3 ubiquitin ligase membrane-associated ring-CH-type finger 8 (MARCHF8). We have recently demonstrated that HPV upregulates MARCHF8 expression in HPV-positive keratinocytes and head and neck cancer (HPV+ HNC) cells. Here, we report that MARCHF8 stabilizes the E7 protein by degrading the components of the SKP1-CUL1-F-box (SCF) ubiquitin ligase complex in HPV+ HNC cells. We found that MARCHF8 knockdown in HPV+ HNC cells drastically decreases the E7 protein level while increasing the CUL1 and UBE2L3 protein levels. We further revealed that the MARCHF8 protein binds to and ubiquitinates CUL1 and UBE2L3 proteins and that MARCHF8 knockdown enhances the ubiquitination of the E7 protein. Conversely, the overexpression of CUL1 and UBE2L3 in HPV+ HNC cells decreases E7 protein levels and suppresses tumor growth in vivo. Our findings suggest that HPV-induced MARCHF8 prevents the degradation of the E7 protein in HPV+ HNC cells by ubiquitinating and degrading CUL1 and UBE2L3 proteins. IMPORTANCESince HPV oncoprotein E7 is essential for virus replication, HPV has to maintain high levels of E7 expression in HPV-infected cells. However, HPV E7 can be efficiently ubiquitinated by a ubiquitin ligase and degraded by proteasomes in the host cell. Mechanistically, the components of the E3 ubiquitin ligase complex CUL1 and UBE2L3 play an essential role in E7 ubiquitination and degradation. Here, we show that the membrane ubiquitin ligase MARCHF8 induced by HPV E6 stabilizes the E7 protein by degrading CUL1 and UBE2L3 and blocking E7 degradation through proteasomes. MARCHF8 knockout restores CUL1 and UBE2L3 expression, decreasing E7 protein levels and inhibiting the proliferation of HPV-positive cancer cells. Additionally, overexpression of CUL1 or UBE2L3 decreases E7 protein levels and suppresses in vivo tumor growth. Our results suggest that HPV maintains high E7 protein levels in the host cell by inducing MARCHF8, which may be critical for cell proliferation and tumorigenesis.

microbiology↗

bioRxiv2023

Early life exposure to cigarette smoke is associated with lung function changes and primes gene expression and DNA methylation changes at Cyp1a1 upon exposure later in life

Prenatal and early life exposure to cigarette smoke (CS) have repeatedly been shown to induce stable, long-term changes in DNA methylation (DNAm) in offspring. It has been hypothesized that these changes might be functionally related to the known outcomes of prenatal and early life CS exposure, which include impaired lung development, altered lung function and increased risk of asthma and wheeze. However, to date, few studies have examined DNAm changes induced by prenatal CS in tissues of the lung, and even fewer have attempted to examine the specific influences of prenatal versus early postnatal exposures. Here, we have established a mouse model of CS exposure which isolates the effects of prenatal and early postnatal CS exposures in early life. We have used this model to measure the effects of prenatal and/or postnatal CS exposures on lung function and immune cell infiltration as well as DNAm and expression of Cyp1a1, a candidate gene previously observed to demonstrate DNAm differences upon CS exposure in humans. Our study revealed that exposure to CS prenatally and in the early postnatal period cause long-lasting differences in offspring lung function, gene expression and lung Cyp1a1 DNAm, which wane over time but are reestablished upon re-exposure to CS in adulthood. This study creates a testable mouse model which can be used to investigate the effects of prenatal and early postnatal CS exposures and will contribute to the design of intervention strategies to mediate these detrimental effects.

genetics↗

bioRxiv2022

HPV E6 upregulates MARCHF8 ubiquitin ligase and inhibits apoptosis by degrading the death receptors in head and neck cancer

The membrane-associated RING-CH-type finger ubiquitin ligase MARCHF8 is a human homolog of the viral ubiquitin ligases Kaposis sarcoma herpesvirus K3 and K5 that promote host immune evasion. Previous studies have shown that MARCHF8 ubiquitinates several immune receptors, such as the major histocompatibility complex II and CD86. While human papillomavirus (HPV) does not encode any ubiquitin ligase, the viral oncoproteins E6 and E7 are known to regulate host ubiquitin ligases. Here, we report that MARCHF8 expression is upregulated in HPV-positive head and neck cancer patients but not in HPV-negative head and neck cancer patients compared to normal individuals. MARCHF8 expression is highly upregulated by HPV oncoprotein E6-induced MYC/MAX transcriptional activation. The knockdown of MARCHF8 expression in human HPV-positive HNC cells restores cell surface expression of the tumor necrosis factor receptor superfamily (TNFRSF) death receptors, FAS, TRAIL-R1, and TRAIL-R2, and enhances apoptosis. MARCHF8 protein directly interacts with and ubiquitinates the TNFRSF death receptors. Further, MARCHF8 knockout in mouse oral cancer cells expressing HPV16 E6 and E7 augments cancer cell apoptosis and suppresses tumor growth in vivo. Our findings suggest that HPV inhibits host cell apoptosis by upregulating MARCHF8 and degrading TNFRSF death receptors in HPV-positive HNC cells. IMPORTANCESince host cell survival is essential for viruses to replicate persistently, many viruses have evolved to prevent host cell apoptosis. The human papillomavirus (HPV) oncoproteins are known to dysregulate proapoptotic proteins. However, our understanding of detailed mechanisms for HPV to inhibit apoptosis is limited. Here, we report that HPV E6 induces transcription of the membrane-associated ubiquitin ligase MARCHF8, which is upregulated in HPV-positive head and neck cancer. MARCHF8 ubiquitinates the tumor necrosis factor receptor superfamily (TNFRSF) death receptors, FAS, TRAIL-R1, and TRAIL-R2 for degradation. We further revealed that downregulation of the death receptors by MARCHF8 prevents cancer cell apoptosis and that knockout of MARCHF8 expression significantly inhibits in vivo tumor growth and enhances tumor-free survival of mice transplanted with mouse oral cancer cells expressing HPV16 E6 and E7.These results suggest that virus-induced degradation of death receptors leads to cancer cell survival in HPV-positive head and neck cancer.

microbiology↗