Hydroxamic Acid and Benzoic Acid–Based STAT3 Inhibitors Suppress Human Glioma and Breast Cancer Phenotypes In Vitro and In Vivo

Abstract

STAT3 offers an attractive target for cancer therapy but small molecule inhibitors with appealing pharmacologic properties have been elusive. Here we report hydroxamic acid-based and benzoic acid-based inhibitors (SH5-07 and SH4-54, respectively) with robust bioactivity. Both inhibitors blocked STAT3 DNA binding activity in vitro and in human glioma, breast, and prostate cancer cells and in v-Src-transformed murine fibroblasts. STAT3-dependent gene transcription was blocked along with Bcl-2, Bcl-xL, Mcl-1, Cyclin D1, c-Myc and Survivin expression. Nuclear magnetic resonance analysis of STAT3-inhibitor complexes defined interactions with the SH2 and DNA binding domains of STAT3. Ectopic expression of the SH2 domain in cells was sufficient to counter the STAT3 inhibitory effects of SH4-54. Neither compound appreciably affected STAT1 or STAT5 DNA binding activities, STAT3-independent gene transcription or activation of a panel of oncogenic kinases in malignant cells. Each compound decreased the proliferation and viability of glioma, breast and prostate cancer cells and v-Src-transformed murine fibroblasts harboring constitutively active STAT3. Further, in mouse xenograft models of glioma and breast cancer, administration of SH5-07 or SH4-54 effectively inhibited tumor growth. Our results offer preclinical proof of concept for SH5-07 and SH4-54 as candidates fof further development as cancer therapeutics.

Disarming an Electrophilic Warhead: Retaining Potency in Tyrosine Kinase Inhibitor (TKI)‐Resistant CML Lines While Circumventing Pharmacokinetic Liabilities

“…In addition, to examine selectivity, AM-1-124 was also assessed in a STAT1 [22] FP assay. FP experiments revealed that AM-1-124 was able to selectively disrupt a STAT3:IL-6R/gp130 peptide complex (Ki = 15.3 μM, Figure 3A) over that of the homologous STAT1:IFN-γ receptor complex (Ki > 250 μM, Figure 3B).…”

Role of STAT3 in Genesis and Progression of Human Malignant Gliomas

“…Since STAT3 activity has been modulated by targeting pSTAT3-Y705 (pharmacological inhibitors, blocking antibodies, and dominant negative proteins) or total STAT3 protein accumulation (RNAi) or STAT3 dimers formation or binding to DNA (decoy oligonucleotides), the role of pSTAT3-S727 remained misunderstood in the cell fate control by STAT3. Interestingly, inhibiting STAT3 dimer formation and DNA-binding by the mean of STA-21, S3I-201 [83], hydroxamic acid-based (SH5-07) and benzoic acid-based inhibitors (SH4-54) [172] STAT3 inhibitors which target the STAT3 SH2 domain resulted in apoptosis or decreased cell proliferation (assessed by low BrdU incorporation). This depended on the state of cell differentiation, on the cell culture conditions and on the profile of STAT3 phosphorylation (pSTAT3-Y705 or pSTAT3-S727).…”

STAT3 and GR cooperate to drive basal-like triple negative breast cancer gene expression and proliferation

“…Inhibiting GR alone is not effective; basal-like cell lines proliferate and express some components of the basal-like gene signature without glucocorticoids in their media. Inhibiting STAT3 alone is not completely effective; previous studies have shown that SH4-54 killed basal-like cell lines in culture, but was insufficient to completely stop tumor growth in vivo where glucocorticoids are naturally present (24). These results indicate that inhibiting either of these TFs alone is not sufficient to abrogate the pro-proliferative gene expression program of basal-like breast cancer in vivo, but this study suggests that inhibiting both GR and STAT3 could be a novel and effective therapeutic strategy.…”

“…Many of these TFs regulate important pathways in basal-like breast cancer and these TFs often regulate each other's expression (22,23). Several of these TFs can be inhibited with small molecule drugs and represent promising therapeutic targets (18,24,25). What remains unclear is which TFs are responsible for driving the gene expression signature that defines the basal-like TNBC subtype and which are downstream of the master regulator.…”