A derivative of epigallocatechin-3-gallate induces apoptosis via SHP-1-mediated suppression of BCR-ABL and STAT3 signalling in chronic myelogenous leukaemia

Tea-break with epigallocatechin gallate derivatives - Powerful polyphenols of great potential for medicine

Epigallocatechin gallate (EGCG) is a polyphenol present in green tea (Camellia sinensis), which has revealed anti-cancer effects toward a variety of cancer cells in vitro and protective potential against neurodegenerative diseases such as Alzheimer's and Parkinson's. Unfortunately, EGCG presents disappointing bioavailability after oral administration, primarily due to its chemical instability and poor absorption. Due to these limitations, EGCG is currently not used in medication, but only as a dietary supplement in the form of green tea extract. Therefore, it needs further modifications before being considered suitable for extensive medical applications. In this article, we review the scientific literature about EGCG derivatives focusing on their biological properties and potential medical applications. The most common chemical modifications of epigallocatechin gallate rely on introducing fatty acid chains or sugar molecules to its chemical structure to modify solubility. Another frequently employed procedure is based on blocking EGCG's hydroxyl groups with various substituents. Novel derivatives reveal interesting properties, of which, antioxidant, anti-inflammatory, antitumor and antimicrobial, are especially important. It is worth noting that the most promising EGCG derivatives present higher stability and activity than base EGCG.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

Synthesis, Stability, and Antidiabetic Activity Evaluation of (-)-Epigallocatechin Gallate (EGCG) Palmitate Derived from Natural Tea Polyphenols

This work describes a novel approach for the synthesis of (−)-epigallocatechin gallate (EGCG) palmitate by a chemical-synthesis method, where the elevated stability of the EGCG derivative is achieved. Various parameters affecting the acylation process, such as the base, solvent, as well as the molar ratio of palmitoyl chloride, have been studied to optimize the acylation procedure. The optimized reaction condition was set as follows: EGCG/palmitoyl chloride/sodium acetate was under a molar ratio of 1:2:2, with acetone as the solvent, and the reaction temperature was 40 °C. Under the optimized condition, the yield reached 90.6%. The EGCG palmitate (PEGCG) was isolated and identified as 4′-O-palmitoyl EGCG. Moreover, the stability of PEGCG under different conditions was proved significantly superior to EGCG. Finally, PEGCG showed better inhibition towards α-amylase and α-glucosidase, which was 4.5 and 52 times of EGCG, respectively. Molecular docking simulations confirmed the in vitro assay results. This study set a novel and practical synthetic approach for the derivatization of EGCG, and suggest that PEGCG may act as an antidiabetic agent.

Phytochemical Targeting of STAT3 Orchestrated Lipid Metabolism in Therapy-Resistant Cancers

Lipids are critical for maintaining homeostasis and cellular metabolism. However, the dysregulation of lipid metabolism contributes to the pathogenesis of chronic inflammatory diseases and is a hallmark of several cancer types. Tumours exist in a microenvironment of poor vascularization-depleted oxygen and restricted nutrients. Under these conditions, tumours have been shown to increasingly depend on the metabolism of fatty acids for sustained proliferation and survival. Signal transducer and activator of transcription 3 (STAT3) plays a key role in cellular processes such as cell growth, apoptosis and lipid metabolism. Aberrant STAT3 activity, as seen in several cancer types, is associated with tumour progression and malignancy, in addition to propagating crosstalk between tumour cells and the microenvironment. Furthermore, STAT3-regulated lipid metabolism is critical for cancer stem cell self-renewal and therapy resistance. Plant-derived compounds known as phytochemicals are a potential source for novel cancer therapeutic drugs. Dietary phytochemicals are known to modulate key cellular signalling pathways involved in lipid homeostasis and metabolism, including the STAT3 signalling pathways. Targeting STAT3 orchestrated lipid metabolism has shown therapeutic promise in human cancer models. In this review, we summarize the antitumour activity of phytochemicals with an emphasis placed on their effect on STAT3-regulated lipid metabolism and their role in abrogating therapy resistance.

EGCG Mediated Targeting of Deregulated Signaling Pathways and Non-Coding RNAs in Different Cancers: Focus on JAK/STAT, Wnt/β-Catenin, TGF/SMAD, NOTCH, SHH/GLI, and TRAIL Mediated Signaling Pathways

Decades of research have enabled us to develop a better and sharper understanding of multifaceted nature of cancer. Next-generation sequencing technologies have leveraged our existing knowledge related to intra- and inter-tumor heterogeneity to the next level. Functional genomics have opened new horizons to explore deregulated signaling pathways in different cancers. Therapeutic targeting of deregulated oncogenic signaling cascades by products obtained from natural sources has shown promising results. Epigallocatechin-3-gallate (EGCG) has emerged as a distinguished chemopreventive product because of its ability to regulate a myriad of oncogenic signaling pathways. Based on its scientifically approved anticancer activity and encouraging results obtained from preclinical trials, it is also being tested in various phases of clinical trials. A series of clinical trials associated with green tea extracts and EGCG are providing clues about significant potential of EGCG to mechanistically modulate wide ranging signal transduction cascades. In this review, we comprehensively analyzed regulation of JAK/STAT, Wnt/β-catenin, TGF/SMAD, SHH/GLI, NOTCH pathways by EGCG. We also discussed most recent evidence related to the ability of EGCG to modulate non-coding RNAs in different cancers. Methylation of the genome is also a widely studied mechanism and EGCG has been shown to modulate DNA methyltransferases (DNMTs) and protein enhancer of zeste-2 (EZH2) in multiple cancers. Moreover, the use of nanoformulations to increase the bioavailability and thus efficacy of EGCG will be also addressed. Better understanding of the pleiotropic abilities of EGCG to modulate intracellular pathways along with the development of effective EGCG delivery vehicles will be helpful in getting a step closer to individualized medicines.

Epigallocatechin-3-Gallate Induces Apoptosis as a TRAIL Sensitizer via Activation of Caspase 8 and Death Receptor 5 in Human Colon Cancer Cells

Though epigallocatechin-3-gallate (EGCG), a major compound of green tea, has anti-diabetes, anti-obesity, anti-inflammatory, and antitumor effects, the underlying antitumor molecular mechanism of EGCG was not fully understood so far. Here the sensitizing effect of EGCG to tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL) was examined in colorectal cancers. Cotreatment of EGCG and TRAIL synergistically enhanced cytotoxicity and sub G1 accumulation, increased the number of terminal deoxynucleotidyl transferase-dT-mediated dUTP nick end labelling (TUNEL)-positive cells in SW480 and HCT116 cells. Furthermore, this cotreatment promoted the cleavages of poly (adenosine diphosphate-ribose) polymerase (PARP) and induced caspase 8 activation compared to TRAIL or EGCG alone in SW480 and HCT116 cells. Of note, cotreatment of EGCG and TRAIL increased the expression of death receptor 5 (DR5) at protein and mRNA levels and also DR5 cell surface level in colon cancer cells. Conversely, depletion of DR5 reduced the apoptotic activity of cotreatment of EGCG and TRAIL to increase cytotoxicity, sub-G1 population and PARP cleavages in colon cancer cells. Overall, our findings provide evidence that EGCG can be a sensitizer of TRAIL via DR5 and caspase 8 mediated apoptosis in colorectal cancer cells.

Leukemia therapy by flavonoids: Future and involved mechanisms

Flavonoids are a varied family of phytonutrients (plant chemicals) usually are detected in fruits and vegetables. In this big family, there exist more than 10,000 members that is separated into six chief subtypes: isoflavonols, flavonoenes, flavones, flavonols, anthocyanins, and chalcones. The natural compounds, such as fruits, have visible positive effects in regulating of survival involved signaling pathways that performance as the regulator of cell survival, growth, and proliferation. Researchers have established that commonly consumption up flavonoids decreases incidence and development risk of certain cancers, especially leukemia. Flavonoids have been able to induce apoptosis and stimulate cell cycle arrest in cancer cells via different pathways. Similarly, they have antiangiogenesis and antimetastasis capability, which were shown in wide ranges of cancer cells, particularly, leukemia. It seems that flavonoid because of their widespread approval, evident safety and low rate of side effects, have hopeful anticarcinogenic potential for leukemia therapy. Based on the last decade reports, the most important acting mechanisms of these natural compounds in leukemia cells are stimulating of apoptosis pathways by upregulation of caspase 3, 8, 9 and poly ADP-ribose polymerase (PARP) and proapoptotic proteins, particularly Bax activation. As well, they can induce cell cycle arrest in target cells not only via increasing of activated levels of p21 and p53 but also by inhibition of cyclins and cyclin-dependent kinases. Furthermore, attenuation of neclear factor-κB and signal transducer and activator of transcription 3 activation, suppression of signaling pathway and downregulation of intracellular antiapoptotic proteins are other significant antileukemic function mechanism of flavonoids. Overall, it appears that flavonoids are promising and effective compounds in the field of leukemia therapy. In this review, we tried to accumulate and revise most promising flavonoids and finally declared their major working mechanisms in leukemia cells.

Derivative of Epigallocatechin-3-gallatea Encapsulated in ZIF-8 with Polyethylene Glycol-Folic Acid Modification for Target and pH-Responsive Drug Release in Anticancer Research

Epigallocatechin-3-gallatea (EGCG), a key component of tea, has been found to have anticancer activity but poor stability. To improve its antioxidative stability and widen the application of EGCG in anticancer therapy, a kind of EGCG derivative, EGCG palmitate (PEGCG), was synthesized and encapsulated in ZIF-8 nanoparticles with functionalization of folic acid (FA), which is commonly used as pH-responsive drug carrier. PEGCG encapsulated in polyethylene glycol (PEG)-FA/ZIF-8 nanoparticles (PEG-FA/PEGCG@ZIF-8 NPs) exhibits sixfold improvement of stability compared to that of free PEGCG. With target recognition between folic acid (FA) on the surface of NPs and overexpressed FA receptor (FR) in cancer cells, the NPs can be efficiently internalized into cells and present targeted effects of inhibition growth on HeLa cells (cancer cells) compared with HEK 293 cells (normal cells), consistent with the regulation of reactive oxygen species (ROS) level and the induction of autophagy. The detection of autophagy flux and the measurement of autophagy marked proteins in cells suggest that autophagy flux and the autophagosome formation are appreciably induced when the cells were treated with PEG-FA/PEGCG@ZIF-8 NPs. It indicates that pH-responsive PEG-FA/PEGCG@ZIF-8 NPs with target identification for cancer cells can be used as highly efficient drug carriers in targeting cancer chemotherapy.

(-)-Epigallocatechin-3-gallate induces cell apoptosis in chronic myeloid leukaemia by regulating Bcr/Abl-mediated p38-MAPK/JNK and JAK2/STAT3/AKT signalling pathways

Epigallocatechin-3-gallate (EGCG), a major polyphenolic constituent of green tea, possesses remarkable chemopreventive and therapeutic potential against various types of cancer, including leukaemia. However, the molecular mechanism involved in chronic myeloid leukaemia (CML), especially imatinib-resistant CML cells, is not completely understood. In the present study, we investigated the effect of EGCG on the growth of Bcr/Abl+ CML cell lines, including imatinib-resistant cell lines and primary CML cells. The results revealed that EGCG could inhibit cell growth and induce apoptosis in CML cells. The mechanisms involved inhibition of the Bcr/Abl oncoprotein and regulation of its downstream p38-MAPK/JNK and JAK2/STAT3/AKT pathways. In conclusion, we documented the anti-CML effects of EGCG in imatinib-sensitive and imatinib-resistant Bcr/Abl+ cells, especially T315I-mutated cells.

Cytoprotective Effect of Epigallocatechin Gallate (EGCG)-5'-O-α-Glucopyranoside, a Novel EGCG Derivative

Epigallocatechin gallate (EGCG) is a well-studied polyphenol with antioxidant effects. Since EGCG has low solubility and stability, many researchers have modified EGCG residues to ameliorate these problems. A novel EGCG derivative, EGCG-5′-O-α-glucopyranoside (EGCG-5′Glu), was synthesized, and its characteristics were investigated. EGCG-5′Glu showed antioxidant effects in cell and cell-free systems. Under SNP-derived radical exposure, EGCG-5′Glu decreased nitric oxide (NO) production, and recovered ROS-mediated cell viability. Moreover, EGCG-5′Glu regulated apoptotic pathways (caspases) and cell survival molecules (phosphoinositide 3-kinase (PI3K) and phosphoinositide-dependent kinase 1 (PDK1)). In another radical-induced condition, ultraviolet B (UVB) irradiation, EGCG-5′Glu protected cells from UVB and regulated the PI3K/PDK1/AKT pathway. Next, the proliferative effect of EGCG-5′Glu was examined. EGCG-5′Glu increased cell proliferation by modulating nuclear factor (NF)-κB activity. EGCG-5′Glu protects and repairs cells from external damage via its antioxidant effects. These results suggest that EGCG-5′Glu could be used as a cosmetics ingredient or dietary supplement.

Targeting oncogenic transcription factors by polyphenols: A novel approach for cancer therapy

Inflammation is one of the major causative factor of cancer and chronic inflammation is involved in all the major steps of cancer initiation, progression metastasis and drug resistance. The molecular mechanism of inflammation driven cancer is the complex interplay between oncogenic and tumor suppressive transcription factors which include FOXM1, NF-kB, STAT3, Wnt/β- Catenin, HIF-1α, NRF2, androgen and estrogen receptors. Several products derived from natural sources modulate the expression and activity of multiple transcription factors in various tumor models as evident from studies conducted in cell lines, pre-clinical models and clinical samples. Further combination of these natural products along with currently approved cancer therapies added an additional advantage and they considered as promising targets for prevention and treatment of inflammation and cancer. In this review we discuss the application of multi-targeting natural products by analyzing the literature and future directions for their plausible applications in drug discovery.

Epigallocatechin-3-gallate induces apoptosis in acute promyelocytic leukemia cells via a SHP-1-p38α MAPK-Bax cascade

Acute promyelocytic leukemia (APL) is characterized by a specific chromosomal translation, resulting in a fusion gene that affects the differentiation, proliferation and apoptosis of APL cells. Epigallocatechin-3-gallate (EGCG), a catechin, exhibits numerous biological functions, including antitumor activities. Previous studies have reported that EGCG induces apoptosis in NB4 cells. However, the molecular mechanism underlying EGCG-induced apoptosis remains unclear. The present study aimed to determine the molecular basis of EGCG-induced apoptosis in NB4 cells. EGCG treatment significantly inhibited the viability of NB4 cells in a dose-dependent manner. In addition, EGCG treatment induced apoptosis and increased the levels of (Bcl-2-like protein 4) Bax protein expression. Moreover, EGCG treatment was able to increase phosphorylated (p)-p38α mitogen-activated protein kinase (MAPK) and Src homology 1 domain-containing protein tyrosine phosphatase (SHP-1) expression. Pretreatment with PD169316 (a p38 MAPK inhibitor) partially blocked EGCG-induced apoptosis and inhibited EGCG-mediated Bax expression. Similarly, pretreatment with NSC87877, an inhibitor of SHP-1, partially blocked EGCG-induced apoptosis and inhibited EGCG-mediated increases in p-p38α MAPK and Bax expression. Therefore, the results of the present study indicate that EGCG is able to induce apoptosis in NB4 cells via the SHP-1-p38αMAPK-Bax cascade.

The Inhibitory Effect of Epigallocatechin Gallate on the Viability of T Lymphoblastic Leukemia Cells is Associated with Increase of Caspase-3 Level and Fas Expression

Acute lymphoblastic leukemia is the most prevalent cancer in children. Novel components to help struggle aggressive malignancies and overcome some side effects of conventional treatments could be a promising strategy. Epigallocatechingallate (EGCG), have attracted the attention of scientists for prevention or treatment of some cancers. Jurkat cells were incubated with the different concentrations of EGCG (30-100 µm) for 24, 48, and 72 h and cell viability was investigated using MTS test. Apoptosis and the level of caspase 3 alterations were evaluated using flowcytometry and expression of Fas by Real Time PCR. EGCG decreased viability of cells with an inhibition concentration (IC50) of 82.8 ± 3.1, 68.8 ± 4 and 59.7 ± 4.8 μM in 24,48 and 72 h. 50, 70 and 100 µM concentrations of EGCG induced apoptosis in about 31, 40 and 71% of the cells, respectively. The mean value of caspase 3 positive cells in the presence of 50, 70 and 100 µm concentrations of EGCG was 19.3 ± 2.9, 29.5 ± 3.1 and 61.2 ± 3.4 respectively compared to 7.8 ± 1.1 in control with a significant difference at 100 µm concentration. Treatment with EGCG for 48 h enhanced the expression of Fas reaching to a significant level at 100 µM concentration. EGCG is effective in decrease cell viability, apoptosis induction and enhancement of caspase 3 and Fas expression level in jurkat cells. A comprehensive understanding of molecular events and pharmacokinetics of the component and experiments in animal models are required for dose determination and its interaction with other components of combination chemotherapy.

WMJ-8-B, a novel hydroxamate derivative, induces MDA-MB-231 breast cancer cell death via the SHP-1-STAT3-survivin cascade

BACKGROUND AND PURPOSE

Histone deacetylase (HDAC) inhibitors have been demonstrate to have broad-spectrum anti-tumour properties and have attracted lots of attention in the field of drug discovery. However, the underlying anti-tumour mechanisms of HDAC inhibitors remain incompletely understood. In this study, we aimed to characterize the underlying mechanisms through which the novel hydroxamate-based HDAC inhibitor, WMJ-8-B, induces the death of MDA-MB-231 breast cancer cells.

EXPERIMENTAL APPROACH

Effects of WMJ-8-B on cell viability, cell cycle distribution, apoptosis and signalling molecules were analysed by the MTT assay, flowcytometric analysis, immunoblotting, reporter assay, chromatin immunoprecipitation analysis and use of siRNAs. A xenograft model was used to determine anti-tumour effects of WMJ-8-B in vivo.

KEY RESULTS

WMJ-8-B induced survivin reduction, G2/M cell cycle arrest and apoptosis in MDA-MB-231 cells. STAT3 phosphorylation, transactivity and its binding to the survivin promoter region were reduced in WMJ-8-B-treated cells. WMJ-8-B activated the protein phosphatase SHP-1 and when SHP-1 signalling was blocked, the effects of WMJ-8-B on STAT3 phosphorylation and survivin levels were abolished. However, WMJ-8-B increased the transcription factor Sp1 binding to the p21 promoter region and enhanced p21 levels. Moreover, WMJ-8-B induced α-tubulin acetylation and disrupted microtubule assembly. Inhibition of HDACs was shown to contribute to WMJ-8-B's actions. Furthermore, WMJ-8-B suppressed the growth of MDA-MB-231 xenografts in mammary fat pads in vivo.

CONCLUSIONS AND IMPLICATIONS

The SHP-1-STAT3-survivin and Sp1-p21 cascades are involved in WMJ-8-B-induced MDA-MB-231 breast cancer cell death. These results also indicate the potential of WMJ-8-B as a lead compound for treatment of breast cancer and warrant its clinical development.

Alteration of SHP-1/p-STAT3 Signaling: A Potential Target for Anticancer Therapy

The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1 (SHP-1), a non-receptor protein tyrosine phosphatase, has been reported as a negative regulator of phosphorylated signal transducer and activator of transcription 3 (STAT3) and linked to tumor development. In this present review, we will discuss the importance and function of SHP-1/p-STAT3 signaling in nonmalignant conditions as well as malignancies, its cross-talk with other pathways, the current clinical development and the potential role of inhibitors of this pathway in anticancer therapy and clinical relevance of SHP-1/p-STAT3 in cancers. Lastly, we will summarize and highlight work involving novel drugs/compounds targeting SHP-1/p-STAT3 signaling and combined strategies that were/are discovered in our and our colleagues’ laboratories.

Nanoparticle Targeting CD44-Positive Cancer Cells for Site-Specific Drug Delivery in Prostate Cancer Therapy

Prostate cancer is one of the leading causes of cancer death in adult men and is a multistage disease with therapeutic challenges of local recurrent advanced tumors and distant metastatic disease. CD44 is a multifunctional and multistructural cell surface glycoprotein that is involved in cell-cell interactions, cell proliferation, and cell migration. In the study, we produced negatively charged and biocompatible hyaluronic acid-based nanoparticles as a therapeutic system for targeting CD44-positive cancer cells. Subsequently, we confirmed the delivery of bioactive epigallocatechin-3-gallate and site-specific inhibition of prostate tumor growth. In this study, hyaluronic acid-based nanoparticles successfully encapsulated epigallocatechin-3-gallate and were efficiently internalized into cancer cells via CD44 ligand receptor recognition, induced cell cycle arrest at G2/M phase, and inhibited prostate cancer cell growth. Furthermore, in vivo assays indicated that these nanoparticles specifically bind CD44 receptors and increase apoptosis of cancer cells, leading to significant decreases in prostate tumor activity and tumor tissue inflammation.

Ethyl acetate extract from Selaginella doederleinii Hieron inhibits the growth of human lung cancer cells A549 via caspase-dependent apoptosis pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Selaginella doederleinii Hieron has been used as a folk medicine for the treatment of different cancers, especially for nasopharyngeal carcinoma, lung cancer and trophoblastic tumor in China. Previously, the ethyl acetate extract from S. doederleinii (SDEA extract) showed favorable anti-cancer potentials. However, the main chemical composition and anticancer mechanism of the SDEA extract were still not very clear. Until now, there are no reports available about the oral toxicity of the extract.

AIM OF STUDY

The present study was to further elucidate the chemical composition and anti-lung cancer mechanism of the SDEA extract, and evaluate the acute oral toxicity of the extract.

MATERIALS AND METHODS

The SDEA extract was separated and analysed by HPLC to disclose its main chemicals. The effects of the extract were then investigated in vitro on cell viability, apoptosis and cell cycle using fluorescence microscopy and flow cytometry, and the molecular mechanism against human lung cancer cells A549 was further studied by western blot assays. The in vivo anti-cancer effect of the extract was evaluated in A549 xenograft mice model by histochemical assay, and tumor growth, microvascular density (MVD) and Ki67 expression were also measured. In addition, acute oral toxicity test of the extract was executed in mice.

RESULTS

SDEA extract mainly contained eight biflavonoids. The extract caused the loss of mitochondrial membrane potential and induced cell apoptosis by upregulating Bax, downregulating Bcl-2, activating caspase-9 and caspase-3 and blocked the cell cycle in S phase. The extract reduced expression of antigen Ki67, decreased MVD, and significantly inhibited the tumor growth. The extract did not show apparent oral acute toxicity in healthy mice.

CONCLUSION

The SDEA extract exerted anti-tumor effect through activating mitochondrial pathways and reducing Ki67 expression and MVD. Low oral acute toxicity suggested it a promising chemotherapy agent.

Hsp90 Inhibitors for the Treatment of Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a hematological malignancy that arises due to reciprocal translocation of 3' sequences from c-Abelson (ABL) protooncogene of chromosome 9 with 5' sequence of truncated break point cluster region (BCR) on chromosome 22. BCR-ABL is a functional oncoprotein p210 that exhibits constitutively activated tyrosine kinase causing genomic alteration of hematopoietic stem cells. BCR-ABL specific tyrosine kinase inhibitors (TKIs) successfully block CML progression. However, drug resistance owing to BCR-ABL mutations and overexpression is still an issue. Heat-shock proteins (Hsps) function as molecular chaperones facilitating proper folding of nascent polypeptides. Their increased expression under stressful conditions protects cells by stabilizing unfolded or misfolded peptides. Hsp90 is the major mammalian protein and is required by BCR-ABL for stabilization and maturation. Hsp90 inhibitors destabilize the binding of BCR-ABL protein thus leading to the formation of heteroprotein complex that is eventually degraded by the ubiquitin-proteasome pathway. Results of many novel Hsp90 inhibitors that have entered into various clinical trials are encouraging. The present review targets the current development in the CML treatment by availing Hsp90 specific inhibitors.