M344: Potent HDAC Inhibitor (IC50 100 nM) for Cancer and HIV-1 Research

Executive Summary: M344 (SKU A4105) is a cell-permeable histone deacetylase (HDAC) inhibitor with nanomolar potency (IC50 = 100 nM), validated for inducing histone acetylation and gene expression modulation in multiple cancer cell lines (APExBIO). It inhibits cell proliferation in breast cancer, neuroblastoma, and medulloblastoma models with GI50 values around 0.63-0.65 μM under standardized conditions. M344 acts via p53-independent pro-apoptotic pathways, modulates NF-κB, and shows efficacy in HIV-1 latency reversal by activating the LTR region. Its solubility profile, storage, and dosing parameters are well-characterized, ensuring reliable integration in experimental workflows (related article). Quantitative claims are grounded in peer-reviewed and product literature, with robust evidence for bench reproducibility and translational relevance.

Biological Rationale

Histone deacetylases (HDACs) regulate gene expression by removing acetyl groups from histone proteins, leading to chromatin condensation and transcriptional repression. Dysregulated HDAC activity contributes to oncogenesis, impaired cell differentiation, and maintenance of viral latency states. HDAC inhibitors, such as M344, are valuable tools for restoring normal gene expression patterns in cancer and infectious disease research. By increasing histone acetylation, M344 promotes open chromatin, facilitating transcription of tumor suppressor and pro-apoptotic genes (APExBIO).

Mechanism of Action of M344

M344 is a small-molecule, cell-permeable HDAC inhibitor with an IC50 of 100 nM against HDAC enzymes as measured in biochemical assays at 37°C, pH 7.4. It inhibits HDACs, leading to increased acetylation of histone H3 and H4 proteins. This epigenetic modulation results in upregulation of genes involved in cell cycle arrest, differentiation, and apoptosis. In diverse cancer cell lines, M344 increases expression of the pro-apoptotic factor Puma via p53-independent signaling. Notably, it also modulates transcription factors such as NF-κB, impacting gene networks beyond canonical tumor suppressor pathways (see review). In HIV-1 models, M344 activates the HIV-1 LTR, contributing to latency reversal strategies.

Evidence & Benchmarks

• M344 inhibits HDAC activity with an IC50 of 100 nM in cell-free enzymatic assays (APExBIO, product page).
• It suppresses proliferation in MCF-7 breast cancer, D341 MED medulloblastoma, and CH-LA 90 neuroblastoma cells with GI50 values of 0.63-0.65 μM (APExBIO, product documentation).
• M344 treatment (1–100 μM, 1–7 days) induces histone H3 acetylation detectable by immunoblotting at ≥1 μM, 24 h (internal reference).
• It enhances radiation response in SCC-35 and SQ-20B human squamous carcinoma cells, as measured by clonogenic survival after combination therapy (APExBIO, product data).
• M344 upregulates Puma and induces apoptosis in a p53-independent manner, confirmed by mRNA/protein quantification post-treatment (APExBIO, technical note).
• It activates HIV-1 LTR-driven gene expression in in vitro latency models at concentrations ≥1 μM (APExBIO, product documentation).

Compared to "M344: Redefining Epigenetic Modulation in Translational Oncology", which explores strategic research design and combinatorial regimens, this article provides granular, verifiable data and explicit experimental benchmarks for direct protocol integration.

Applications, Limits & Misconceptions

M344 is validated for use in cancer cell line models (e.g., MCF-7, D341 MED, CH-LA 90) and HIV-1 latency assays. It is suited for workflows including apoptosis assays, cell differentiation studies, and synergy with radiation therapy. The compound's solubility parameters (≥14.75 mg/mL in DMSO, ≥12.88 mg/mL in ethanol with ultrasonication) facilitate stock preparation for in vitro applications. M344 is not intended for in vivo clinical use or as a diagnostic/therapeutic agent in humans. Its effects are cell-type and context-dependent; not all cell lines respond equivalently. Long-term storage of M344 in solution is not recommended due to chemical instability at room temperature or above. It must be handled under appropriate laboratory conditions, shipped with blue ice, and stored at −20°C as a solid.

Common Pitfalls or Misconceptions

• M344 is not soluble in water; improper solvent selection can result in precipitation and assay failure.
• Long-term storage in solution form at ≥4°C leads to compound degradation and loss of potency.
• The compound is for research use only; it is not approved for diagnostic or medical applications.
• Effects in non-cancerous primary cells are not well-characterized; generalization beyond validated cell lines is not supported.
• M344 does not replace pan-HDAC inhibitors in all contexts; selectivity and efficacy should be empirically verified for each experimental system.

For further discussion of workflow reliability and troubleshooting, see "M344 (SKU A4105): Reliable HDAC Inhibition for Robust Cell Assays", which specifically addresses reproducibility and assay sensitivity challenges not covered in this summary.

Workflow Integration & Parameters

M344 is supplied as a solid by APExBIO. Reconstitution is recommended in DMSO (≥14.75 mg/mL) or ethanol (≥12.88 mg/mL with ultrasonication). Stock solutions should be aliquoted and stored at -20°C, protected from light; repeated freeze-thaw cycles are discouraged. Typical working concentrations range from 1 μM to 100 μM, with exposure times from 24 h up to 7 days depending on assay endpoint. M344 is compatible with cell viability, apoptosis, and histone acetylation assays. For reliable results, solvent controls and parallel untreated samples are mandatory. For HIV-1 latency reversal, LTR activation is typically measured by reporter gene expression after 24–48 h exposure at ≥1 μM. Users are referred to the M344 product page for detailed protocols and safety information. This article extends "M344: Potent HDAC Inhibitor with IC50 100 nM for Cancer Research" by detailing solvent compatibility, storage, and concentration-response parameters for reproducible workflows.

Conclusion & Outlook

M344 (A4105) is a validated, potent, and cell-permeable HDAC inhibitor suitable for a wide range of cancer and HIV-1 latency research applications. Its quantifiable activity, defined solubility, and storage parameters support robust experimental design. By modulating histone acetylation, M344 enables mechanistic studies of gene regulation, cell fate, and therapeutic synergy. Ongoing research continues to refine its utility in combinatorial regimens and new disease models. For complete specifications and ordering, see the APExBIO M344 product page.