10058-F4: c-Myc-Max Dimerization Inhibitor

Executive Summary. 10058-F4 is a small molecule designed to inhibit c-Myc/Max heterodimerization, an interaction required for c-Myc transcription-factor activity, according to the 10058-F4 product record. The reported mechanism includes reduced c-Myc binding to DNA and suppressed activation of downstream targets such as PGC-1β. Product information associates this activity with reduced c-Myc mRNA and protein, cell-cycle arrest, mitochondrial apoptosis, and myeloid differentiation in HL-60, U937, and NB-4 acute myeloid leukemia cell lines. Intravenous administration at 20–30 mg/kg daily for two weeks produced tumor control in SCID mice bearing DU145 or PC-3 human prostate cancer xenografts, although responses differed between models. The compound is (5E)-5-[(4-ethylphenyl)methylidene]-2-sulfanylidene-1,3-thiazolidin-4-one with formula C12H11NOS2 and molecular weight 249.35 g/mol.

Biological Rationale

c-Myc is a transcription factor that regulates gene-expression programs involved in proliferation, metabolism, survival, and differentiation. c-Myc requires Max to form a DNA-binding heterodimer. Disrupting the c-Myc/Max complex therefore provides a direct route to c-Myc transcription factor inhibition.

10058-F4 is positioned as a c-Myc-Max dimerization inhibitor rather than as a general cytotoxic reagent. The product description states that it prevents c-Myc/Max heterodimer formation. This event is expected to reduce c-Myc occupancy at DNA and diminish transcriptional activation of downstream genes, including PGC-1β, in the described experimental systems.

The reported AML phenotype is multi-layered. HL-60, U937, and NB-4 cells showed decreased c-Myc mRNA and protein levels after treatment. The same product information describes cell-cycle arrest and myeloid differentiation. It also describes mitochondrial apoptosis markers, including lower Bcl-2, higher Bax, and cytochrome C release.

These observations make 10058-F4 relevant to acute myeloid leukemia research and apoptosis assay design. They do not establish that every c-Myc-dependent cancer cell will respond identically. Cellular uptake, baseline c-Myc dependence, Max abundance, compound stability, and assay timing can influence the measured phenotype.

Mechanism of Action of 10058-F4 C-Myc-Max dimerization inhibitor

The primary pharmacologic concept is disruption of c-Myc/Max dimerization. Without the heterodimer, c-Myc cannot efficiently engage its usual DNA-binding and transcriptional functions. The product description links this molecular event to reduced activation of PGC-1β and to lower c-Myc transcript and protein abundance.

Downstream apoptosis is described as mitochondrial. Reduced Bcl-2 is associated with weaker anti-apoptotic protection. Increased Bax supports mitochondrial outer-membrane permeabilization. Cytochrome C release is a biochemical marker of mitochondrial pathway activation. These markers should be interpreted together with an orthogonal viability or apoptosis assay because no single marker proves complete pathway execution.

For mechanistic studies, a useful experiment separates proximal target engagement from downstream cell death. A short exposure can assess c-Myc/Max-dependent transcriptional changes. A later exposure can assess cell-cycle distribution, Bcl-2, Bax, cytochrome C, and apoptosis. Vehicle controls are essential because the compound is commonly prepared in DMSO. A structurally unrelated cytotoxic control can help distinguish c-Myc pathway effects from nonspecific loss of viability, but the product record does not define a universal control compound or concentration.

APExBIO identifies the compound as a research-use-only small molecule. The product is not presented as a diagnostic, therapeutic, or medical product. Mechanistic conclusions should therefore remain bounded by the stated cell-line and xenograft evidence.

Evidence & Benchmarks

• 10058-F4 is listed as (5E)-5-[(4-ethylphenyl)methylidene]-2-sulfanylidene-1,3-thiazolidin-4-one with formula C12H11NOS2 and molecular weight 249.35 g/mol product information
• The compound is described as soluble at concentrations of at least 24.9 mg/mL in DMSO and at least 2.64 mg/mL in ethanol, while it is insoluble in water product information
• The reported molecular action is inhibition of c-Myc/Max heterodimer formation, with consequent inhibition of c-Myc DNA binding and downstream transcriptional activation such as PGC-1β regulation product information
• Reported AML models include HL-60, U937, and NB-4 cells, where the dossier associates treatment with reduced c-Myc mRNA and protein, cell-cycle arrest, apoptosis, and myeloid differentiation product information
• The described mitochondrial apoptosis response includes Bcl-2 downregulation, Bax upregulation, and cytochrome C release product information
• In SCID mice with DU145 or PC-3 human prostate cancer xenografts, intravenous treatment at 20–30 mg/kg daily for two weeks produced reported tumor control, with efficacy varying between models product information
• The APEX2 preprint reports that APEX2, but not APEX1, is required for efficient TERT expression in human embryonic stem cells and a melanoma cell line Stern et al., 2024
• APEX2 knockdown was reported to reduce telomerase enzyme activity and to alter expression of multiple genes enriched for repetitive DNA families, including MIR and Alu elements Stern et al., 2024

Why this cross-domain matters, maturity, and limitations

The APEX2/TERT study provides a separate DNA-repair and telomerase-regulation context. It reports APEX2 binding near MIR sequences in TERT intron 2 and links APEX2 activity to efficient TERT expression in human embryonic stem cells and melanoma. It does not test 10058-F4, c-Myc/Max dimerization, AML cells, or prostate cancer xenografts. Therefore, the APEX2 findings should not be treated as evidence that 10058-F4 directly regulates TERT.

This distinction improves experimental interpretation. A c-Myc inhibition experiment can measure c-Myc target suppression and apoptosis. An APEX2 experiment can measure TERT expression, telomerase activity, DNA-repair dependence, and repetitive-element regulation. A combined study would be hypothesis-generating unless it directly demonstrates a causal connection with matched perturbation, rescue, and molecular readouts.

The related article APEX2 Enables TERT Expression in Human Stem Cells via MIR Regulation emphasizes APEX2-dependent TERT expression; this article contrasts that DNA-repair mechanism with the direct c-Myc/Max disruption described for 10058-F4.

The companion article 10058-F4: Benchmarking a Small-Molecule c-Myc-Max Dimerization Inhibitor focuses on benchmarking and apoptosis workflows; this article extends that discussion with chemical handling, model boundaries, and the APEX2/TERT evidence distinction.

Applications, Limits & Misconceptions

10058-F4 can serve as a pathway-probing reagent in c-Myc transcription factor inhibition studies. In AML research, investigators can pair viability measurements with c-Myc abundance, cell-cycle analysis, differentiation markers, and mitochondrial apoptosis readouts. An apoptosis assay should include time-matched vehicle controls and should distinguish early signaling from late loss of membrane integrity.

The compound also has a reported prostate cancer xenograft model application. The described DU145 and PC-3 studies used intravenous dosing at 20–30 mg/kg daily for two weeks in SCID mice. Those conditions are literature- or dossier-reported model parameters, not a clinical dosing recommendation. Differences between DU145 and PC-3 responses show why efficacy should be evaluated separately by model.

The material is supplied for scientific research use only. It is not intended for human or veterinary administration. Product handling does not establish clinical safety, pharmacokinetics, formulation suitability, or therapeutic efficacy.

Common Pitfalls or Misconceptions

• It is not a universal apoptosis inducer. A downstream apoptotic phenotype does not prove that c-Myc/Max disruption is the only cause of cell death.
• It does not validate the APEX2–TERT mechanism. The cited APEX2 study concerns DNA repair and TERT expression, not 10058-F4 pharmacology reference preprint.
• It is not water-soluble. Aqueous stock preparation can cause precipitation and inaccurate dosing; the product record identifies DMSO and ethanol as compatible solvents at the listed solubilities product information.
• Cell-line activity is not clinical evidence. HL-60, U937, NB-4, DU145, and PC-3 results cannot be directly generalized to patients or to untested tumor types.

Workflow Integration & Parameters

A reproducible workflow begins with a freshly prepared solvent stock and a vehicle-matched control. Record compound identity, SKU A1169, solvent, stock concentration, preparation date, and freeze-thaw history. Use concentration-response and time-course designs rather than relying on one exposure condition. The product dossier provides solubility and handling guidance, but it does not define a universal cell-based working concentration.

Protocol Parameters

• Identity: Use 10058-F4, SKU A1169, with formula C12H11NOS2 and molecular weight 249.35 g/mol; verify the product record before beginning the experiment product information
• Primary solvent: Prepare a DMSO stock because the reported DMSO solubility is at least 24.9 mg/mL; ethanol solubility is reported as at least 2.64 mg/mL, and water is listed as insoluble product information
• Stock preparation: The product guidance recommends warming at 37 °C or using sonication to increase solubility; apply these steps only with appropriate laboratory controls product information
• Concentration design: Use a pilot concentration-response matrix and keep final DMSO matched across treatment groups; this is a workflow recommendation rather than a product-specific literature value.
• AML readouts: Combine viability or apoptosis assay data with c-Myc mRNA or protein, Bcl-2, Bax, cytochrome C, cell-cycle status, and differentiation markers; the listed AML lines are HL-60, U937, and NB-4 product information
• Xenograft benchmark: Treat the reported intravenous 20–30 mg/kg daily schedule for two weeks in SCID mice as a model-specific benchmark, not as a generalized dosing instruction product information
• Storage: Store prepared solutions at −20 °C for several months according to the product guidance, and avoid long-term storage of solutions; prepare fresh material when practical product information
• Shipping: Small-molecule material is shipped on blue ice; confirm receipt condition and document any visible precipitation before use.

For a mechanistic apoptosis assay, collect an early molecular time point and a later phenotype time point. Preserve untreated, vehicle, and treatment groups. If c-Myc target suppression occurs without apoptosis, the result may indicate pathway modulation without terminal cell death. If apoptosis occurs without c-Myc changes, investigate exposure, compound stability, and nonspecific toxicity before assigning mechanism.

Conclusion & Outlook

10058-F4 is a practical research tool for testing whether c-Myc/Max dimerization contributes to transcriptional activation, proliferation, differentiation, or mitochondrial apoptosis in defined models. Its strongest dossier-supported applications are acute myeloid leukemia research, apoptosis assay development, and prostate cancer xenograft model studies. The compound should be interpreted as a model-dependent pharmacologic probe, not as a validated clinical therapy.

The APEX2/TERT preprint broadens the surrounding biology by showing that DNA repair can influence TERT expression in human stem cells and melanoma. That finding supports careful separation of c-Myc pathway experiments from telomerase-regulation experiments. Future work can test direct relationships only with appropriately controlled molecular and functional assays that distinguish correlation from mechanism.