# Carbazole Derivatives as STAT Inhibitors: An Overview
## 3 STATs Inhibitors
### Carbazoles as STAT Inhibitors
Moreover, they established that the disruption of STAT3- DNMT1 interaction by **15** is dependent on the deacetylation of STAT3 at K685. Furthermore, starting from the assumption that the STAT3-DNMT1 interaction is important for DNA methylation in the promoter region of TS genes, they identified four TS genes that were demethylated by **15** in HS578T cells, among which the retinoic acid receptor beta (RARB), neurogenic 1 (NEUROG1), PDZ and LIM domain 4 (PDLIM4), and Von Hippel-Lindau tumor suppressor (VHL). Then, they evaluated the methylation status of these promoters in two TNBC cells. It has been discovered that the promoter regions of VHL and PDLIM4 genes were highly methylated and **15** near commonly demethylated these promoters. Demethylation of VHL and PDLIM4 gene promoters by **15** resulted in the reactivation of mRNA expression of these genes in both HS578T and MDA-MB-231 in a dose-dependent manner. At the end, they carried out in vivo studies, highlighting that **15** significantly reduced tumor growth without inducing loss of body weight [111]. In 2015, [PERSON] et al. [113] studied the antitumor properties of **16** (Figure 11), a hybrid indolocarbazole analog produced by combinatorial biosynthesis of Rebecamycin and Staurosporine genes. The authors outlined the antiproliferative activity of this compound towards HS578T, BT549, MDA-MB-231, and HCC3153 with IC\({}_{50}\) values in the nanomolar range. Moreover, **16** was able to reduce colony formation of these cells and decrease tumor volume in mice. Besides, their main purpose was to investigate the molecular mechanism of **16** by analyzing its effects on kinases profile in TNBC. Through biochemical experiments, they proved that **16** suppressed downstream components of the PI3K/AKT pathway includingAKT (phosphorylated at T308 and S473) and p56. In the same way, it suppressed p-Stat3 and p-Stat1 in HS578T and BT549 cells. To deepen their knowledge of the antiproliferative mechanism, they carried out some experiments on cell cycle and apoptosis. Their findings suggested that it caused an accumulation of cells HS578T, BT549, and MDA-MB-231 in G2/M phase at 24h whereas further analysis underlined that the apoptotic mechanism was caspases independent. Therefore, to examine if **16** induced DNA damage, they evaluated the phosphorylated \(\gamma\)H2 AX levels, a protein necessary for checkpoint-mediated cell cycle arrest and DNA repair following double-stranded DNA breaks. Treatment with **16** in HS578T, BT549, and MDA-MB-231 exhibited an enhancement in the phosphorylated levels of \(\gamma\)H2 AX at early time points. They also noted that **16** provoked the phosphorylation of p53 and Chk2, validating the induction of DNA damage. In addition, they tried to explore the effects of **16** when associated with chemotherapeutic agents used in the clinical setting for triple negative tumors such as vinorelbine, docetaxel, and carboplatin. Their results displayed a synergistic interaction of **16** with all these compounds, mostly with docetaxel, in HS578T, BT549, and MDA-MB-231 cells and improved effects _in vivo_. In addition, **16** possessed a good pharmacodynamic and pharmacokinetic profile. Indeed, it exhibited a clear decrease of p56 and pSTAT1 at 30 min in vivo in the extracted tumors. pSTAT3 was also moderately impaired. Induction of p\(\gamma\)H2 AX was reached at 60 min. Moreover, they evaluated the concentration of the drug in two resected tumors per time point, assessing a time-dependent accumulation, reaching over 1000 ng/g. The obtained results underlined that targeting acetylation of STAT3 (K685) by small molecule inhibitors could be a valid therapeutic option for cancer treatment. Acetylation of STAT3 and DNMT1 present high levels in a wide range of malignancy. Conceivably, in these diseases, the STAT3-DNMT1 complex is engaged in the repression of TS genes by DNA methylation.