In HCT-116 cells, a 24-hour tasisulam concentration series reduced RBM23 and RBM39 protein signals. The study reports AdooQ A13070 as its tasisulam source; this documents historical use rather than validation of a current product lot. [2]
In SUIT2 and A549 cancer cells, 48-hour tasisulam treatment reduced KRAS4A mRNA and protein while comparatively preserving KRAS4B. RBM39 protein was also reduced. These cell-based observations do not establish tasisulam efficacy in animals. [3]
Tasisulam promotes DCAF15–RBM39 association despite weak receptor binding
Biochemical assay · Purified human DDB1–DCAF15 and fluorescent RBM39 RRM2; labeled E7820 probe in receptor competition assay [1]
Protein recruitment and probe competition give distinct binding endpoints; neither is a cellular IC50.
Literature-Reported Treatment Conditions
- Treatment concentration
- 50 μM tasisulam for RBM39 protein titration; 0.002–100 μM aryl-sulfonamide range in competition assay
- Exposure duration
- 15 min at room temperature before measurement for the protein titration (Online Methods)
- Method
- Purified-protein TR-FRET; E7820 and indisulam comparators
- Vehicle
- DMSO; compound dispensation in the general assay method was normalized to 2% DMSO
- Reported limits
- Supplementary no-compound curves were not acquired/viewed. Do not interpret these binding endpoints as degradation potency.
Methods and source locations
Compound reported in the paper: Tasisulam (LY573636); Compound label in the paper: Tasisulam
Evidence applies to the material and model reported in this paper; no salt conversion or current catalog-lot validation is implied.
Fig. 1a,c and caption; Results: RBM39 recruitment to CRL4DCAF15 depends on sulfonamides; Online Methods: TR-FRET
Apparent affinity of RBM39 RRM2 for DDB1–DCAF15 in the presence of 50 μM tasisulam: TR-FRET protein titration; mean ± s.d., three independent replicates (n = 3). Value reported in text/caption, not estimated from curve. — Fig. 1a caption and recruitment Results
Competition with labeled E7820 for DCAF15 binding: TR-FRET competition; Fig. 1c caption reports compound range 0.002–100 μM, DDB1–DCAF15 200 nM and labeled E7820 5 μM; mean ± s.d., n = 3 independent replicates. — Fig. 1c and recruitment Results
Tasisulam occupies the DCAF15–RBM39 interface in a crystal structure
Biochemical assay · Engineered human DDB1ΔB–DCAF15split–DDA1–RBM39 RRM2 complex [1]
The tasisulam-bound structure places the compound in the DCAF15 surface pocket occupied by related aryl sulfonamides.
Literature-Reported Treatment Conditions
- Treatment concentration
- 30 μM tasisulam in compound-exchange/gel-filtration buffer; this is a preparation condition, not an efficacy dose
- Method
- X-ray structure determination after compound exchange from an E7820-bound complex
- Reported limits
- Supplementary electron-density panels and crystallographic statistics were not acquired. No quantitative structural validation statistic or cellular activity is inferred.
Methods and source locations
Compound reported in the paper: Tasisulam (LY573636); Compound label in the paper: Tasisulam
Evidence applies to the material and model reported in this paper; no salt conversion or current catalog-lot validation is implied.
Fig. 4b,d and caption; Results: Aryl-sulfonamides interact primarily with DCAF15; Online Methods: crystallization and structure determination
Location of tasisulam in the protein complex: X-ray crystallography of an engineered protein complex; structure image and chemical drawing inspected. No resolution or interaction-distance measurement adopted. — Fig. 4b,d; aryl-sulfonamide binding Results; Data and materials availability
Tasisulam lowers RBM23 and RBM39 protein levels in HCT-116 cells
Cell-based study · HCT-116 cells with endogenous RBM23 C-terminally tagged with 3xFLAG [2]
A 24-hour concentration series showed decreased RBM23–3xFLAG and RBM39 immunoblot signal relative to the zero-compound lane.
Literature-Reported Treatment Conditions
- Treatment concentration
- 0, 0.08, 0.2, 0.7, 2.2, 6.7 and 20 μM (labels in Fig. 5B)
- Exposure duration
- 24 h
- Method
- Single-agent concentration series followed by immunoblotting
- Reported limits
- Vehicle composition and biological replicate number are not specified for Fig. 5B in the inspected caption/methods. No DC50 was derived.
Methods and source locations
Compound reported in the paper: Tasisulam (LY573636); Compound label in the paper: Tasisulam
Evidence applies to the material and model reported in this paper; no salt conversion or current catalog-lot validation is implied.
Fig. 5B and caption; RBM23 Results; STAR Methods: Key Resources Table and cell culture
RBM23–3xFLAG protein abundance: FLAG-HRP Western blot; anti-actin loading control and zero-compound lane. No densitometric percentage, DC50 or replicate n assigned. — Fig. 5B, tasisulam panel and caption
RBM39 protein abundance: Anti-RBM39 immunoblot in the same concentration-series design; anti-actin loading control. — Fig. 5B, anti-RBM39 row in tasisulam panel
Tasisulam preferentially reduces KRAS4A expression in SUIT2 and A549 cells
Cell-based study · SUIT2 pancreatic cancer and A549 lung cancer cells [3]
After 48 hours, tasisulam reduced KRAS4A transcript and protein signals while KRAS4B was comparatively preserved; RBM39 protein was also reduced.
Literature-Reported Treatment Conditions
- Treatment concentration
- 5, 10 and 20 μM for transcript panels and SUIT2 protein panel; 5 and 10 μM for A549 protein panel
- Exposure duration
- 48 h
- Method
- Single-agent treatment with no-inhibitor control; other inhibitors tested separately
- Reported limits
- Supplier, salt form and drug vehicle were not established from the inspected main text. Supplementary AsPC1 results were not read; claims restricted to main-figure models.
Methods and source locations
Compound reported in the paper: Tasisulam (LY573636); Compound label in the paper: Tasisulam
Evidence applies to the material and model reported in this paper; no salt conversion or current catalog-lot validation is implied.
Fig. 3A-F and caption; Results: Splicing of KRAS4A is regulated by RBM39; Methods: qPCR and Western blotting
Relative KRAS4A and KRAS4B mRNA expression: TaqMan analysis normalized to HPRT1; mean ± s.e.m., n = 4 independent experiments; one-way ANOVA with Tukey multiple comparison. No bar heights or exact P values inferred. — Fig. 3A-D and caption
KRAS4A, KRAS4B and RBM39 protein levels: Western blot with β-actin control; no exact fold-change extracted from printed densitometry. — Fig. 3E-F and caption
