Inhibition of thymidine phosphorylase expression by using an HSP90 inhibitor potentiates the cytotoxic effect of cisplatin in non-small-cell lung cancer cells

Heat shock protein 90 inhibitor 17-AAG down-regulates thymidine phosphorylase expression and potentiates the cytotoxic effect of tamoxifen and erlotinib in human lung squamous carcinoma cells

Elevated thymidine phosphorylase (TP) levels, a key enzyme in the pyrimidine nucleoside salvage pathway, in cancer cells, are related to a poor prognosis in a variety of cancers. Heat shock protein 90 (Hsp90) is a ubiquitous molecular chaperone that is involved in the stabilization and maturation of many oncogenic proteins. The aim of this study is to elucidate whether Hsp90 inhibitor 17-AAG could enhance tamoxifen- and erlotinib-induced cytotoxicity in nonsmall cell lung cancer (NSCLC) cells via modulating TP expression in two squamous NSCLC cell lines, H520 and H1703. We found that 17-AAG reduced TP expression via inactivating the MKK1/2-ERK1/2-mitogen-activated protein kinase (MAPK) pathway. TP knockdown with siRNA or ERK1/2 MAPK inactivation with the pharmacological inhibitor U0126 could enhance the cytotoxic and growth inhibitory effects of 17-AAG. In contrast, MKK1-CA or MKK2-CA (a constitutively active form of MKK1/2) vector-enforced expression could reduce the cytotoxic and cell growth inhibitory effects of 17-AAG. Furthermore, 17-AAG enhanced the cytotoxic and cell growth inhibitory effects of tamoxifen and erlotinib in NSCLC cells, which were associated with TP expression downregulation and MKK1/2-ERK1/2 signal inactivation. Taken together, Hsp90 inhibition downregulates TP, enhancing the tamoxifen- and erlotinib-induced cytotoxicity in H520 and H1703 cells.

Quantitative analysis of differentially expressed proteins in psoriasis vulgaris using tandem mass tags and parallel reaction monitoring

Background

Psoriasis vulgaris (PV) is a chronic autoimmune inflammatory disease with epidermal hyperkeratosis and parakeratosis.

Methods

The study was to elucidate the pathogenesis of PV by quantitative proteomic analysis of skin lesion biopsies of PV and healthy tissues with tandem mass tags (TMTs) coupled with liquid chromatography–mass spectrometry (LC–MS)/MS.

Results

A total of 4562 differentially expressed proteins (DEPs) between PV lesional tissues (n = 11) and healthy tissues (n = 11) were identified, of which 299 were upregulated and 206 were downregulated using |fold change| > 1.3 as the cutoff threshold. The Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the DEPs were mainly enriched in the activation of immune cells (drug metabolism pathway, NOD-like pathway, and IL-17 pathway), cell proliferation (ribosomal pathway, DNA replication pathway, and base replication pathway), metabolism-related pathways (fatty acid biosynthesis and metabolism, PPAR pathway, glycerophospholipid metabolism, and cortisol synthesis and breakdown), and glandular secretion (saliva secretion, gastric acid secretion, and pancreatic fluid secretion). Thirteen DEPs that were relatively highly expressed in the drug metabolism pathway were validated with parallel reaction monitoring (PRM), of which MPO, TYMP, IMPDH2, GSTM4, and ALDH3A1 were highly expressed in PV, whereas CES1, MAOB, MGST1, and GSTT1 were less expressed in PV.

Conclusions

These findings confirmed that these proteins participate in the drug metabolism-other enzyme pathways and play crucial roles in the activation and proliferation of immune cells in the pathogenesis of PV.

Hsp90B enhances MAST1-mediated cisplatin resistance by protecting MAST1 from proteosomal degradation

Microtubule-associated serine/threonine kinase 1 (MAST1) is a central driver of cisplatin resistance in human cancers. However, the molecular mechanism regulating MAST1 levels in cisplatin-resistant tumors is unknown. Through a proteomics screen, we identified the heat shock protein 90 B (hsp90B) chaperone as a direct MAST1 binding partner essential for its stabilization. Targeting hsp90B sensitized cancer cells to cisplatin predominantly through MAST1 destabilization. Mechanistically, interaction of hsp90B with MAST1 blocked ubiquitination of MAST1 at lysines 317 and 545 by the E3 ubiquitin ligase CHIP and prevented proteasomal degradation. The hsp90B-MAST1-CHIP signaling axis and its relationship with cisplatin response were clinically validated in cancer patients. Furthermore, combined treatment with a hsp90 inhibitor and the MAST1 inhibitor lestaurtinib further abrogated MAST1 activity and consequently enhanced cisplatin-induced tumor growth arrest in a patient-derived xenograft model. Our study not only uncovers the regulatory mechanism of MAST1 in tumors but also suggests a promising combinatorial therapy to overcome cisplatin resistance in human cancers.

Inhibition of thymidine phosphorylase expression by Hsp90 inhibitor potentiates the cytotoxic effect of salinomycin in human non-small-cell lung cancer cells

Salinomycin is a polyether ionophore antibiotic having anti-tumorigenic property in various types of cancer. Elevated thymidine phosphorylase (TP) levels, a key enzyme in the pyrimidine nucleoside salvage pathway, are associated with an aggressive disease phenotype and poor prognoses. Heat shock protein 90 (Hsp90) is a ubiquitous molecular chaperone that is responsible for the stabilization and maturation of many oncogenic proteins. In this study, we report whether Hsp90 inhibitor 17-AAG could enhance salinomycin-induced cytotoxicity in NSCLC cells through modulating TP expression in two non-small-cell lung cancer (NSCLC) cell lines, A549 and H1975. We found that salinomycin increased TP expression in a MKK3/6-p38 MAPK activation manner. Knockdown of TP using siRNA or inactivation of p38 MAPK by pharmacological inhibitor SB203580 enhanced the cytotoxic and growth inhibition effects of salinomycin. In contrast, enforced expression of MKK6E (a constitutively active form of MKK6) reduced the cytotoxicity and cell growth inhibition of salinomycin. Moreover, Hsp90 inhibitor 17-AAG enhanced cytotoxicity and cell growth inhibition of salinomycin in NSCLC cells, which were associated with down-regulation of TP expression and inactivation of p38 MAPK. Together, the Hsp90 inhibition induced TP down-regulation involved in enhancing the salinomycin-induced cytotoxicity in A549 and H1975 cells.

Molecular mechanism and targeted therapy of Hsp90 involved in lung cancer: New discoveries and developments (Review)

The exploration of the molecular mechanisms and signaling pathways on lung cancer is very important for developing new strategies of diagnosis and treatment to this disease, such as finding valuable lung cancer markers and molecularly targeted therapies. Previously, a number of studies disclose that heat shock protein 90 (Hsp90) is upregulated in cancer cells, tissues and serum of lung cancer patients, and its upregulation intimately correlates with the occurrence, development and outcome of lung cancer. On the contrary, inhibition of Hsp90 can suppress cell proliferation, motility and metastasis of lung cancer and promote apoptosis of lung cancer cells via complex signaling pathways. In addition, a series of Hsp90 inhibitors have been investigated as effective molecular targeted therapy tactics fighting against lung cancer. This review, systematically summarizes the role of Hsp90 in lung cancer, the molecular mechanisms and development of anti-Hsp90 treatment in lung cancer.

Thymidine phosphorylase: A potential new target for treating cardiovascular disease

We recently found that thymidine phosphorylase (TYMP), also known as platelet-derived endothelial cell growth factor, plays an important role in platelet activation in vitro and thrombosis in vivo by participating in multiple signaling pathways. Platelets are a major source of TYMP. Since platelet-mediated clot formation is a key event in several fatal diseases, such as myocardial infarction, stroke and pulmonary embolism, understanding TYMP in depth may lead to uncovering novel mechanisms in the development of cardiovascular diseases. Targeting TYMP may become a novel therapeutic for cardiovascular disorders. In this review article, we summarize the discovery of TYMP and the potential molecular mechanisms of TYMP involved in the development of various diseases, especially cardiovascular diseases. We also offer insights regarding future studies exploring the role of TYMP in the development of cardiovascular disease as well as in therapy.

Thymidine Phosphorylase in Cancer; Enemy or Friend?

Thymidine phosphorylase (TP) is a nucleoside metabolism enzyme that plays an important role in the pyrimidine pathway.TP catalyzes the conversion of thymidine to thymine and 2-deoxy-α-D-ribose-1-phosphate (dRib-1-P). Although this reaction is reversible, the main metabolic function of TP is catabolic. TP is identical to the angiogenic factor platelet-derived endothelial-cell growth factor (PD-ECGF). TP is overexpressed in several human cancers in response to cellular stressful conditions like hypoxia, acidosis, chemotherapy and radiotherapy. TP has been shown to promote tumor angiogenesis, invasion, metastasis, evasion of the immune-response and resistance to apoptosis. Some of the biological effects of TP are dependent on its enzymatic activity, while others are mediated through cytokines like interleukin 10 (IL-10), basic fibroblast growth factor (bFGF) and tumour necrosis factor α (TNFα). Interestingly, TP also plays a role in cancer treatment through its role in the conversion of the oral fluoropyrimidine capecitabine into its active form 5-FU. TP is a predictive marker for fluoropyrimidine response. Given its various biological functions in cancer progression, TP is a promising target in cancer treatment. Further translational research is required in this area.

Characterization of the mammalian miRNA turnover landscape

Steady state cellular microRNA (miRNA) levels represent the balance between miRNA biogenesis and turnover. The kinetics and sequence determinants of mammalian miRNA turnover during and after miRNA maturation are not fully understood. Through a large-scale study on mammalian miRNA turnover, we report the co-existence of multiple cellular miRNA pools with distinct turnover kinetics and biogenesis properties and reveal previously unrecognized sequence features for fast turnover miRNAs. We measured miRNA turnover rates in eight mammalian cell types with a combination of expression profiling and deep sequencing. While most miRNAs are stable, a subset of miRNAs, mostly miRNA*s, turnovers quickly, many of which display a two-step turnover kinetics. Moreover, different sequence isoforms of the same miRNA can possess vastly different turnover rates. Fast turnover miRNA isoforms are enriched for 5′ nucleotide bias against Argonaute-(AGO)-loading, but also additional 3′ and central sequence features. Modeling based on two fast turnover miRNA*s miR-222-5p and miR-125b-1-3p, we unexpectedly found that while both miRNA*s are associated with AGO, they strongly differ in HSP90 association and sensitivity to HSP90 inhibition. Our data characterize the landscape of genome-wide miRNA turnover in cultured mammalian cells and reveal differential HSP90 requirements for different miRNA*s. Our findings also implicate rules for designing stable small RNAs, such as siRNAs.

Hsp90 inhibitor as a sensitizer of cancer cells to different therapies (review)

Hsp90 is a molecular chaperone that maintains the structural and functional integrity of various client proteins involved in signaling and many other functions of cancer cells. The natural inhibitors, ansamycins influence the Hsp90 chaperone function by preventing its binding to client proteins and resulting in their proteasomal degradation. N- and C-terminal inhibitors of Hsp90 and their analogues are widely tested as potential anticancer agents in vitro, in vivo as well as in clinical trials. It seems that Hsp90 competitive inhibitors target different tumor types at nanomolar concentrations and might have therapeutic benefit. On the contrary, some Hsp90 inhibitors increased toxicity and resistance of cancer cells induced by heat shock response, and through the interaction of survival signals, that occured as side effects of treatments, could be very effectively limited via combination of therapies. The aim of our review was to collect the data from experimental and clinical trials where Hsp90 inhibitor was combined with other therapies in order to prevent resistance as well as to potentiate the cytotoxic and/or antiproliferative effects.

Ganetespib, a novel Hsp90 inhibitor in patients with KRAS mutated and wild type, refractory metastatic colorectal cancer

BACKGROUND

Heat shock protein 90 (Hsp90) is a cellular chaperone that is required for the maturation and stability of a variety of proteins that play key roles in colon cancer initiation and progression. The primary objective of the current study was to define the safety and efficacy of ganetespib, a novel, selective small-molecule Hsp90 inhibitor, in patients with refractory metastatic colorectal cancer.

PATIENTS AND METHODS

The study was a single-arm, Simon 2-stage, phase II trial for patients with chemotherapy-refractory, metastatic colorectal cancer. Patients received ganetespib 200 mg/m(2) intravenously. Tumor tissue was collected before treatment and 48 hours after treatment for changes in expression of Hsp90 client proteins and other potential pharmacodynamics markers. V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), v-Raf murine sarcoma viral oncogene homolog B, and phosphatidylinositol-4, 5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutational status was also determined.

RESULTS

Seventeen patients were treated (median age, 58; range, 44-79 years). No patients demonstrated objective regression of disease. Two patients had stable disease of 6.8 and 5.1 months duration. Serious adverse events that were potentially attributable to ganetespib included diarrhea (12%, n = 2), fatigue (17%, n = 3), and increased aspartate aminotransferase/alanine aminotransferase (12%, n = 2) and alkaline phosphatase (6%, n = 1) levels. Of the 17 evaluable patients, 9 (53%) including patients with stable disease as best response, had KRAS-mutant tumors.

CONCLUSION

In this first phase II investigation of an Hsp90 inhibitor in colorectal cancer, ganetespib as a single agent did not demonstrate activity in chemotherapy-refractory metastatic colorectal cancer. However, on the basis of the drug's promising preclinical combination data and the relatively mild toxicity profile, further clinical investigation of this agent in combination with standard cytotoxic agents is planned.

Dual targeting of heat shock proteins 90 and 70 promotes cell death and enhances the anticancer effect of chemotherapeutic agents in bladder cancer

Heat shock proteins (HSPs), which are molecular chaperones that stabilize numerous vital proteins, may be attractive targets for cancer therapy. The aim of the present study was to investigate the possible anticancer effect of single or dual targeting of HSP90 and HSP70 and the combination treatment with HSP inhibitors and chemotherapeutic agents in bladder cancer cells. The expression of HSP90 and the anticancer effect of the HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) coupled with cisplatin, docetaxel, or gemcitabine were examined using immunohistochemistry, quantitative real-time PCR, cell growth, flow cytometry, immunoblots and caspase-3/7 assays. The expression of HSP70 under HSP90 inhibition and the additive effect of HSP70 inhibitor pifithrin-μ (PFT-μ) were examined by the same assays and transmission electron microscopy. HSP90 was highly expressed in bladder cancer tissues and cell lines. 17-AAG enhanced the antiproliferative and apoptotic effects of each chemotherapeutic agent. 17-AAG also suppressed Akt activity but induced the upregulation of HSP70. PFT-μ enhanced the effect of 17-AAG or chemotherapeutic agents; the triple combination of 17-AAG, PFT-μ and a chemotherapeutic agent showed the most significant anticancer effect on the T24 cell line. The combination of 17-AAG and PFT-μ markedly suppressed Akt and Bad activities. With HSP90 suppression, HSP70 overexpression possibly contributes to the avoidance of cell death and HSP70 may be a key molecule for overcoming resistance to the HSP90 inhibitor. The dual targeting of these two chaperones and the combination with conventional anticancer drugs could be a promising therapeutic option for patients with advanced bladder cancer.

The HSP90 inhibitor 17-N-allylamino-17-demethoxy geldanamycin (17-AAG) synergizes with cisplatin and induces apoptosis in cisplatin-resistant esophageal squamous cell carcinoma cell lines via the Akt/XIAP pathway

Although cisplatin (CDDP) is a key drug in the treatment of esophageal squamous cell carcinoma (ESCC), acquired chemoresistance remains a major problem. Combination therapy may represent one strategy to overcome this resistance. Heat shock protein 90 (HSP90) is known to be overexpressed in several types of cancer cells, and its inhibition by small molecules, either alone or in combination, has shown promise in the treatment of solid malignancies. In the present study, we evaluated the synergistic effects of combining CDDP with the HSP90 inhibitor 17-N-allylamino-17-demethoxy geldanamycin (17-AAG) on two CDDP-resistant human esophageal squamous cancer cell lines, KYSE30 and KYSE150. The results obtained demonstrated the synergistic inhibitory effects of CDDP and 17-AAG on the growth of KYSE30 and KYSE150 cells. Cell growth and cell number were more effectively reduced by the combined treatment with CDDP and 17-AAG than by the treatment with either CDDP or 17-AAG alone. Western blotting revealed that the combined action of CDDP and 17-AAG cleaved poly (ADP-ribose) polymerase (PARP) and caspase-3, which demonstrated that the reduction in both cell growth and cell number was mediated by apoptosis. Time-course experiments showed that reduction in X-linked inhibitor of apoptosis protein (XIAP) and phosphorylated Akt were concomitant with apoptosis. The results of the present study demonstrate that 17-AAG synergizes with CDDP and induces apoptosis in CDDP-resistant ESCC cell lines, and also that modulation of the Akt/XIAP pathway may underlie this synergistic effect. Combination therapy with CDDP and an HSP90 inhibitor may represent a promising strategy to overcome CDDP resistance in ESCC.

Hsp90 inhibition by PU-H71 induces apoptosis through endoplasmic reticulum stress and mitochondrial pathway in cancer cells and overcomes the resistance conferred by Bcl-2

Heat shock protein 90 (Hsp90) has recently emerged as an attractive therapeutic target in cancer treatment because of its role in stabilizing the active form of a wide range of client oncoproteins. This study investigated the mechanism of apoptosis induced by the purine-scaffold Hsp90 inhibitor PU-H71 in different human cancer cell lines and examined the role of Bcl-2 and Bax in this process. We demonstrated that Hsp90 inhibition by PU-H71 generated endoplasmic reticulum (ER) stress and activated the Unfolded Protein Response (UPR) as evidenced by XBP1 mRNA splicing and up-regulation of Grp94, Grp78, ATF4 and CHOP. In response to PU-H71-induced ER stress, apoptosis was triggered in melanoma, cervix, colon, liver and lung cancer cells, but not in normal human fibroblasts. Apoptosis was executed through the mitochondrial pathway as shown by down-regulation of Bcl-2, up-regulation and activation of Bax, permeabilization of mitochondrial membranes, release of cytochrome c and activation of caspases. We also found that, in contrast to the ER stressor thapsigargin, PU-H71 induced apoptosis in cells overexpressing Bcl-2 and thus overcame the resistance conferred by this anti-apoptotic protein. In addition, although Bax deficiency rendered cells resistant to PU-H71, combined treatment with the anticancer drugs cisplatin or melphalan greatly sensitized these cells to PU-H71. Taken together, these data suggest that inhibition of Hsp90 by PU-H71 is a promising strategy for cancer treatment, particularly in the case of tumors resistant to conventional chemotherapy.