Precision targeting of AML by suppressing HERV-K102: Treating cancer through “cell explosion”
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Background: Reactivation of an ancient, dormant virus A substantial portion of the human genome consists of human endogenous retroviruses (HERVs), remnants of past viral infections. Although usually dormant, HERV-K102, one such element, has been found to be abnormally active in patients with acute myeloid leukemia (AML), helping cancer cells proliferate.
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An innovative approach: Removing cancer cells’ protective layer (K-Env) with CRISPR The research team used CRISPR-Cas9 gene-editing technology to remove K-Env, the envelope protein of HERV-K102. However, because the primers used in this study were based on shared HERV-K sequences, they could not specifically measure HERV-K102 at the mRNA level.
- Suppressed proliferation: AML cells lacking K-Env showed sharply slowed growth.
- Induced cell death: Beyond simply dying, the cells began a specialized form of cell death.
- Key mechanism: Induction of inflammatory cell death, pyroptosis The study’s main finding is that K-Env deficiency may induce pyroptosis, an intense form of cell death.
- Pathway: Caspase-1 is activated inside the cell and cleaves the gasdermin D protein. The cleaved protein forms pores in the cell membrane, causing the cell to swell and eventually burst.
- Evidence: Increased LDH release outside the cell and protein cleavage suggest pyroptosis. However, these markers can also overlap with apoptosis or secondary necrosis, so functional validation using specific inhibitors is needed.
- Demonstrating therapeutic efficacy in a mouse model Effects were also confirmed in living organisms (in vivo).
- Inhibited tumor growth: Selective removal of K-Env in a mouse transplantation model markedly suppressed tumor growth.
- Tumor growth monitoring: Average luminescence signals were measured over 14 days to monitor tumor growth in vivo, showing the potential of a new AML treatment strategy targeting HERV-K102.
- Outlook: Potential for next-generation AML immunotherapy When cells burst during pyroptosis, they send inflammatory signals to their surroundings, recruiting immune cells to the site. This study therefore points to the potential for developing a new AML immunotherapy strategy.
OBJECTIVE: Several recent studies have focused on human endogenous retroviruses (HERVs). HERVs entered the human genome millions of years ago and are associated with various diseases including cancer and immune regulation. Among these, the HERV-K family exhibits the highest transcriptional activity. However, little is known about the expression of HERVs in acute myeloid leukemia (AML) and their potential as biomarkers or therapeutic targets. This study primarily investigated the role of HERV-K102 in AML development and explored the underlying mechanisms. METHODS: The expression profiles of HERV K102 in AML and normal samples were analyzed using The Cancer Genome Atlas (TCGA) database and AML cell lines. Knockout models were generated using CRISPR-Cas9-mediated deletion of the HERV-K102 envelope (K-Env). Cell viability and pyroptosis rates were measured using the MTT assay and flow cytometry, respectively. Transcriptome analysis was performed to identify differentially expressed genes and related pathways. Pyroptosis markers were detected using qRT-PCR and western blotting. The role of HERV-K102 in AML was validated using an inducible knockout xenograft tumor model. RESULTS: HERV-K102 was aberrantly activated and highly expressed in AML cells. K-Env depletion inhibited AML cell proliferation and promoted apoptosis. Furthermore, K-Env knockout induced pyroptosis, as indicated by increased lactate dehydrogenase (LDH) release and enhanced cleavage of caspase-1 and gasdermin D (GSDMD). Transcriptomic and functional analyses demonstrated that this process is mediated by S100A9 upregulation and activation of the NOD-like receptor protein 3 (NLRP3) inflammasome pathway. CONCLUSION: Our findings suggest that HERV-K102 Env may play an important role in AML pathogenesis and represents a novel diagnostic and therapeutic target.
AML is a difficult-to-treat blood cancer. With existing targets limited, this study presents HERV-K102 as a new biomarker and therapeutic target. Targeting the HERV-K102 envelope protein has the potential to lead to the development of new AML immunotherapy strategies.