Responses to Dasatinib as a Second- and Third-Line Tyrosine Kinase Inhibitor in Chronic Phase Chronic Myeloid Leukaemia Patients.

We retrospectively evaluated the efficacy and safety of dasatinib among 48 Chinese patients with chronic phase chronic myeloid leukaemia. The proportions of patients achieving the optimal molecular responses at 3, 6, and 12 months, a major molecular response (MMR) rate and a complete cytogenetic response (CCyR) rate were 87.0, 87.0, 72.2, 45.8, and 72.7% for patients with dasatinib as second-line therapy, and 34.8, 34.8, 33.3, 20.8, and 46.2% as third-line therapy, respectively. A BCR-ABL1 transcript level on the International Scale (BCR-ABL1IS) of ≤10% at the initiation of -dasatinib treatment was found to be associated with a higher probability of achieving MMR. Among patients with a -BCR-ABL1IS higher than 10% at initiation of dasatinib treatment, dasatinib showed better performance as a second-line therapy than as a third-line therapy. The patients who achieved an optimal molecular response at 3 months had a superior cumulative incidence of MMR and CCyR compared with patients who failed to achieve such a response. Dasatinib induced considerable responses as a second-line treatment, especially in patients with a BCR-ABL1IS ≤10% at initiation of treatment, whereas the efficacy was limited in patients receiving third-line therapy with a BCR-ABL1IS >10% at the initiation of treatment.

The K-Ras effector p38γ MAPK confers intrinsic resistance to tyrosine kinase inhibitors by stimulating EGFR transcription and EGFR dephosphorylation.

Mutations in K-Ras and epidermal growth factor receptor (EGFR) are mutually exclusive, but it is not known how K-Ras activation inactivates EGFR, leading to resistance of cancer cells to anti-EGFR therapy. Here, we report that the K-Ras effector p38γ MAPK confers intrinsic resistance to small molecular tyrosine kinase inhibitors (TKIs) by concurrently stimulating EGFR gene transcription and protein dephosphorylation. We found that p38γ increases EGFR transcription by c-Jun-mediated promoter binding and stimulates EGFR dephosphorylation via activation of protein-tyrosine phosphatase H1 (PTPH1). Silencing the p38γ/c-Jun/PTPH1 signaling network increased sensitivities to TKIs in K-Ras mutant cells in which EGFR knockdown inhibited growth. Similar results were obtained with the p38γ-specific pharmacological inhibitor pirfenidone. These results indicate that in K-Ras mutant cancers, EGFR activity is regulated by the p38γ/c-Jun/PTPH1 signaling network, whose disruption may be a novel strategy to restore the sensitivity to TKIs.

p38γ MAPK Is a Therapeutic Target for Triple-Negative Breast Cancer by Stimulation of Cancer Stem-Like Cell Expansion.

Triple-negative breast cancer (TNBC) is highly progressive and lacks established therapeutic targets. p38γ mitogen-activated protein kinase (MAPK) (gene name: MAPK12) is overexpressed in TNBC but how overexpressed p38γ contributes to TNBC remains unknown. Here, we show that p38γ activation promotes TNBC development and progression by stimulating cancer stem-like cell (CSC) expansion and may serve as a novel therapeutic target. p38γ silencing in TNBC cells reduces mammosphere formation and decreases expression levels of CSC drivers including Nanog, Oct3/4, and Sox2. Moreover, p38γ MAPK-forced expression alone is sufficient to stimulate CSC expansion and to induce epithelial cell transformation in vitro and in vivo. Furthermore, p38γ depends on its activity to stimulate CSC expansion and breast cancer progression, indicating a therapeutic opportunity by application of its pharmacological inhibitor. Indeed, the non-toxic p38γ specific pharmacological inhibitor pirfenidone selectively inhibits TNBC growth in vitro and/or in vivo and significantly decreases the CSC population. Mechanistically, p38γ stimulates Nanog transcription through c-Jun/AP-1 via a multi-protein complex formation. These results together demonstrate that p38γ can drive TNBC development and progression and may be a novel therapeutic target for TNBC by stimulating CSC expansion. Inhibiting p38γ activity with pirfenidone may be a novel strategy for the treatment of TNBC.

[Evaluation of the rapid trehalose test for the identification of the Candida glabrata].

OBJECTIVE: To explore a rapid and cost-effective method for identification of Candida glabrata through the comparison of two different methods, using molecular methods of sequencing as gold standard. METHODS: From our clinic, 200 strains of suspected Candida glabrata were collected during the last 3 years and selected after incubation in CHROMagar Candida medium for 48 h. By comparing the results of the CHROMagar Candida medium, the identification of the rapid trehalose test for different kinds of strains were analyzed under incubation in the tubes for 3 h, 6 h, and 24 h at 37 °C and 42 °C, respectively. All the strains were identified to species level by methods of sequencing. The optimal time and temperature of the trehalose test for the identification of Candida glabrata were assessed. Two different methods, CHROMagar Candida medium and the rapid trehalose test, in identification of Candida glabrata were compared. RESULTS: In all the 200 strains, Candida glabrata ferment trehalose with 3 h incubation under 42 °C were the optimal time and temperature for fermenting trehalose. The accuracy, sensitivity, and specificity of the rapid trehalose test were 99.00% (198/200), 98.66% (147/149) and 100.00% (51/51). The accuracy rate of CHROMagar Candida medium was 79.50% (159/200), the sensitivity and specificity were only 89.93% (134/149) and 49.02% (25/51), however, compared with the domestic current popular methods, the rapid trehalose test had better time efficiency ratio. CONCLUSION: The evaluation results suggest that the rapid trehalose test has advantages in terms of operational convenience and low cost, and the results can be obtained in 3 h. Therefore, it has application value in clinical laboratory.

p38γ Mitogen-activated protein kinase signals through phosphorylating its phosphatase PTPH1 in regulating ras protein oncogenesis and stress response.

Phosphatase plays a crucial role in determining cellular fate by inactivating its substrate kinase, but it is not known whether a kinase can vice versa phosphorylate its phosphatase to execute this function. Protein-tyrosine phosphatase H1 (PTPH1) is a specific phosphatase of p38γ mitogen-activated protein kinase (MAPK) through PDZ binding, and here, we show that p38γ is also a PTPH1 kinase through which it executes its oncogenic activity and regulates stress response. PTPH1 was identified as a substrate of p38γ by unbiased proteomic analysis, and its resultant phosphorylation at Ser-459 occurs in vitro and in vivo through their complex formation. Genetic and pharmacological analyses showed further that Ser-459 phosphorylation is directly regulated by Ras signaling and is important for Ras, p38γ, and PTPH1 oncogenic activity. Moreover, experiments with physiological stimuli revealed a novel stress pathway from p38γ to PTPH1/Ser-459 phosphorylation in regulating cell growth and cell death by a mechanism dependent on cellular environments but independent of canonical MAPK activities. These results thus reveal a new mechanism by which a MAPK regulates Ras oncogenesis and stress response through directly phosphorylating its phosphatase.

p38γ mitogen-activated protein kinase (MAPK) confers breast cancer hormone sensitivity by switching estrogen receptor (ER) signaling from classical to nonclassical pathway via stimulating ER phosphorylation and c-Jun transcription.

Estrogen receptor (ER) α promotes breast cancer growth by regulating gene expression through classical estrogen response element (ERE) binding and nonclassical (interaction with c-Jun at AP-1 sites) pathways. ER is the target for anti-estrogens such as tamoxifen (TAM). However, the potential for classical versus nonclassical ER signaling to influence hormone sensitivity is not known. Moreover, anti-estrogens frequently activate several signaling cascades besides the target ER, and the implications of these "off-target" signaling events have not been explored. Here, we report that p38γ MAPK is selectively activated by treatment with TAM. This results in both phosphorylation of ER at Ser-118 and stimulation of c-Jun transcription, thus switching ER signaling from the classical to the nonclassical pathway leading to increased hormone sensitivity. Unexpectedly, phosphorylation at Ser-118 is required for ER to bind both p38γ and c-Jun, thereby promoting ER relocation from ERE to AP-1 promoter sites. Thus, ER/Ser-118 phosphorylation serves as a central mechanism by which p38γ regulates signaling transduction of ER with its inhibitor TAM.

p38γ MAPK Inflammatory and Metabolic Signaling in Physiology and Disease.

p38γ MAPK (also called ERK6 or SAPK3) is a family member of stress-activated MAPKs and has common and specific roles as compared to other p38 proteins in signal transduction. Recent studies showed that, in addition to inflammation, p38γ metabolic signaling is involved in physiological exercise and in pathogenesis of cancer, diabetes, and Alzheimer's disease, indicating its potential as a therapeutic target. p38γphosphorylates at least 19 substrates through which p38γ activity is further modified to regulate life-important cellular processes such as proliferation, differentiation, cell death, and transformation, thereby impacting biological outcomes of p38γ-driven pathogenesis. P38γ signaling is characterized by its unique reciprocal regulation with its specific phosphatase PTPH1 and by its direct binding to promoter DNAs, leading to transcriptional activation of targets including cancer-like stem cell drivers. This paper will review recent findings about p38γ inflammation and metabolic signaling in physiology and diseases. Moreover, we will discuss the progress in the development of p38γ-specific pharmacological inhibitors for therapeutic intervention in disease prevention and treatment by targeting the p38γ signaling network.

Phosphorylation and stabilization of topoisomerase IIα protein by p38γ mitogen-activated protein kinase sensitize breast cancer cells to its poisons.

Cancer drugs suppress tumor cell growth by inhibiting specific cellular targets. However, most drugs also activate several cellular nonspecific stress pathways, and the implications of these off-target effects are mostly unknown. Here, we report that p38γ, but not p38α, MAPK is specifically activated by treatment of breast cancer cells with topoisomerase II (Topo II) drugs, whereas paclitaxel (Taxol) does not have this effect. The activated p38γ in turn phosphorylates and stabilizes Topo IIα protein, and this enhances the growth inhibition by Topo II drugs. Moreover, p38γ activity was shown to be necessary and sufficient for Topo IIα expression, the drug-p38γ-Topo IIα axis is only detected in intrinsically sensitive but not resistant cells, and p38γ is co-overexpressed with Topo IIα protein in primary breast cancers. These results reveal a new paradigm in which p38γ actively regulates the drug-Topo IIα signal transduction, and this may be exploited to increase the therapeutic activity of Topo II drugs.

Isoform-specific and cell/tissue-dependent effects of p38 MAPKs in regulating inflammation and inflammation-associated oncogenesis.

p38 MAPK (mitogen-activated protein kinases) family proteins (α, ß, γ and δ) are key inflammatory kinases and play an important role in relaying and processing intrinsic and extrinsic signals in response to inflammation, stress, and oncogene to regulate cell growth, cell death and cell transformation. Recent studies in genetic mouse models revealed that p38α in epithelial cells mostly suppresses whereas in immune cells it promotes inflammation and inflammation-associated oncogenesis. On the contrary, p38γ and p38δ signaling in immune and epithelial cells is both pro-inflammatory and oncogenic. This review summarizes recent discoveries in this field, discusses possible associated mechanisms, and highlights potentials of systemically targeting isoform-specific p38 MAPKs. Understanding of p38 MAPK isoform-specific and cell/tissue- and perhaps stage-dependent effects and their integrated regulated activity in inflammation and in inflammation-associated oncogenesis is essential for effectively targeting this group of kinases for therapeutic intervention.

p38gamma MAPK cooperates with c-Jun in trans-activating matrix metalloproteinase 9.

Mitogen-activated protein kinases (MAPKs) regulate gene expression through transcription factors. However, the precise mechanisms in this critical signal event are largely unknown. Here, we show that the transcription factor c-Jun is activated by p38gamma MAPK, and the activated c-Jun then recruits p38gamma as a cofactor into the matrix metalloproteinase 9 (MMP9) promoter to induce its trans-activation and cell invasion. This signaling event was initiated by hyperexpressed p38gamma that led to increased c-Jun synthesis, MMP9 transcription, and MMP9-dependent invasion through p38gamma interacting with c-Jun. p38gamma requires phosphorylation and its C terminus to bind c-Jun, whereas both c-Jun and p38gamma are required for the trans-activation of MMP9. The active p38gamma/c-Jun/MMP9 pathway also exists in human colon cancer, and there is a coupling of increased p38gamma and MMP9 expression in the primary tissues. These results reveal a new paradigm in which a MAPK acts both as an activator and a cofactor of a transcription factor to regulate gene expression leading to an invasive response.

p38γ MAPK Is Essential for Aerobic Glycolysis and Pancreatic Tumorigenesis.

KRAS is mutated in most pancreatic ductal adenocarcinomas (PDAC) and yet remains undruggable. Here, we report that p38γ MAPK, which promotes PDAC tumorigenesis by linking KRAS signaling and aerobic glycolysis (also called the Warburg effect), is a novel therapeutic target. p38γ interacted with a glycolytic activator PFKFB3 that was dependent on mutated KRAS. KRAS transformation and overexpression of p38γ increased expression of PFKFB3 and glucose transporter GLUT2, conversely, silencing mutant KRAS, and p38γ decreased PFKFB3 and GLUT2 expression. p38γ phosphorylated PFKFB3 at S467, stabilized PFKFB3, and promoted their interaction with GLUT2. Pancreatic knockout of p38γ decreased p-PFKFB3/PFKFB3/GLUT2 protein levels, reduced aerobic glycolysis, and inhibited PDAC tumorigenesis in KPC mice. PFKFB3 and GLUT2 depended on p38γ to stimulate glycolysis and PDAC growth and p38γ required PFKFB3/S467 to promote these activities. A p38γ inhibitor cooperated with a PFKFB3 inhibitor to blunt aerobic glycolysis and PDAC growth, which was dependent on p38γ. Moreover, overexpression of p38γ, p-PFKFB3, PFKFB3, and GLUT2 in PDAC predicted poor clinical prognosis. These results indicate that p38γ links KRAS oncogene signaling and aerobic glycolysis to promote pancreatic tumorigenesis through PFKFB3 and GLUT2, and that p38γ and PFKFB3 may be targeted for therapeutic intervention in PDAC. SIGNIFICANCE: These findings show that p38γ links KRAS oncogene signaling and the Warburg effect through PFKBF3 and Glut2 to promote pancreatic tumorigenesis, which can be disrupted via inhibition of p38γ and PFKFB3.

p38gamma mitogen-activated protein kinase integrates signaling crosstalk between Ras and estrogen receptor to increase breast cancer invasion.

Ras is believed to stimulate invasion and growth by different effector pathways, and yet, the existence of such effectors under physiologic conditions has not been shown. Estrogen receptor (ER), on the other hand, is both anti-invasive and proliferative in human breast cancer, with mechanisms for these paradoxical actions remaining largely unknown. Our previous work showed an essential role of p38gamma mitogen-activated protein kinase in Ras transformation in rat intestinal epithelial cells, and here, we show that p38gamma integrates invasive antagonism between Ras and ER to increase human breast cancer invasion without affecting their proliferative activity. Ras positively regulates p38gamma expression, and p38gamma in turn mediates Ras nonmitogenic signaling to increase invasion. Expression of the Ras/p38gamma axis, however, is trans-suppressed by ER that inhibits invasion and stimulates growth also by distinct mechanisms. Analysis of ER and its cytoplasmic localized mutant reveals that ER additionally binds to p38gamma protein, leading to its specific down-regulation in the nuclear compartment. A p38gamma-antagonistic activity of ER was further shown in a panel of breast cancer cell lines and was shown independent of estrogens by both ER depletion and ER expression. These results revealed that both Ras and ER use distinct pathways to regulate breast cancer growth and invasion, and that p38gamma specifically integrates their antagonistic activity to stimulate cell invasion. Selective targeting of p38gamma-dependent invasion pathways may be a novel strategy to control breast cancer progression.

Targeting an oncogenic kinase/phosphatase signaling network for cancer therapy.

Protein kinases and phosphatases signal by phosphorylation and dephosphorylation to precisely control the activities of their individual and common substrates for a coordinated cellular outcome. In many situations, a kinase/phosphatase complex signals dynamically in time and space through their reciprocal regulations and their cooperative actions on a substrate. This complex may be essential for malignant transformation and progression and can therefore be considered as a target for therapeutic intervention. p38γ is a unique MAPK family member that contains a PDZ motif at its C-terminus and interacts with a PDZ domain-containing protein tyrosine phosphatase PTPH1. This PDZ-coupled binding is required for both PTPH1 dephosphorylation and inactivation of p38γ and for p38γ phosphorylation and activation of PTPH1. Moreover, the p38γ/PTPH1 complex can further regulate their substrates phosphorylation and dephosphorylation, which impacts Ras transformation, malignant growth and progression, and therapeutic response. This review will use the p38γ/PTPH1 signaling network as an example to discuss the potential of targeting the kinase/phosphatase signaling complex for development of novel targeted cancer therapy.

Idiopathic thrombocytopenic purpura: pathogenesis and potential therapeutic approach.

BACKGROUND: This study sought to clarify the pathogenesis of idiopathic thrombocytopenic purpura (ITP) and make preliminary investigations regarding a therapeutic approach. METHODS: Enzyme-linked immunosorbent assay was used to establish and analyze the standard curve for interferon (IFN) γ, interleukin (IL) 4, and IL-17 in order to determine a measurement method for these cytokines. Subsequently, cellular levels of IFN-γ, IL-4, and IL-17 in the peripheral blood of patients in the treatment group (traditional Chinese medicine) was compared with those in the control group (Western-style care). An ITP mice model was also established and treated with different medications. RESULTS: Th1/Th2 cell quantities in ITP patients were significantly higher than in healthy individuals (P<0.05). Furthermore, IL-17 secreted by Th17 cells was significantly higher in ITP patients than healthy individuals (P<0.01). A combination of traditional Chinese medicine and Western-style care yielded the best treatment effect for ITP mice, followed by Western medicine alone and then Chinese medicine alone. CONCLUSIONS: The experimental results suggested that Th17 cells may be more related to the pathogenesis of ITP, and that application of Western-style care supplemented by traditional Chinese medicine may yield a more optimal treatment for ITP.

Molecular epidemiology of colistin-resistant Enterobacteriaceae in inpatient and avian isolates from China: high prevalence of mcr-negative Klebsiella pneumoniae.

Whether chromosomal and transmissible mechanisms contribute simultaneously to colistin resistance in Klebsiella pneumoniae and Escherichia coli remains unknown. This study aims to identify the underlying mechanisms of colistin resistance in inpatient and avian K. pneumoniae and E. coli in China. We retrospectively screened 2353 Enterobacteriaceae isolates from inpatients at multiple centers during 2011-2014, and 168 avian isolates from one slaughterhouse in 2013 for the presence of MCR-1/MCR-2. Mutations and transcriptional levels of the chromosomal RamA, PhoPQ, and PmrAB genes were determined by PCR and RT-qPCR. The transferability and genetic characteristics of the underlying colistin-resistance genes were detected by conjugation and whole-genome sequencing. The MIC90 for colistin in colistin-resistant K. pneumoniae (ColRKP, 128 mg/L, N = 17) was 16-fold higher than in colistin-resistant E. coli (ColREC, 8 mg/L, N = 33). The dominant sequence types of ColRKP were ST2018 and ST37, whereas ColREC displayed diversity. The chromosomal genes ramA, pmrB, and phoQ were not associated with colistin resistance in ColRKP. The transcriptional levels of PmrB in ColREC were 7.5-fold greater than in colistin-susceptible isolates. The carrying rates of MCR-1 in ColREC and ColRKP were 100% (33/33) and 23.5% (4/17), respectively. Plasmid IncI2 (~60 kb) carrying MCR-1 could be transferred to recipient E. coli EC600 with frequencies ranging from 8.74 × 10-6 to 1.31 × 10-4. No transferable genes were identified in mcr-1-negative ColRKP. MCR-1 combined with upregulated PmrB was associated with low-level colistin resistance in ColREC. However, two-thirds of the ColRKP isolates were mcr-negative and need to be studied further.

[Study on the association between gestational diabetes mellitus and tumor necrosis factor-alpha gene polymorphism].

OBJECTIVE: To study allelic frequency of tumor necrosis factor-alpha (TNF-alpha) in gestational diabetes mellitus (GDM) of Han ethnicity in north China and to determine whether there is a specific allele of TNF-alpha associated with GDM susceptibility. METHODS: By using PCR-RFLP, we detected the distribution of TNF-alpha promoter alleles frequency in GDM women and control normal pregnant women. Plasma TNF-alpha levels and insulin levels were measured by radioimmunoassay. RESULTS: (1) There was a significant increase of A alleles frequency of TNF-alpha promoter -308 gene in GDM women compared with control group (61.4% vs 30.0%, P < 0.05) and an increase of the AA + GA genotype was observed in GDM group (71.4% vs 37.1%, P < 0.05). (2) In GDM group, the patients carrying the AA + GA genotype had higher plasma TNF-alpha levels (52 +/- 13 vs 14 +/- 4, P < 0.05) and a lower insulin sensitivity (13.6 +/- 6.5 vs 1.9 +/- 0.2, P < 0.05) compared with those carrying the other genotype (GG). CONCLUSIONS: The 308 G-->A polymorphism of TNF-alpha promoter gene is involved in the pathophysiology of insulin resistance and gestational diabetes mellitus.

[Study on association between gestational diabetes mellitus and sulfonylurea receptor-1 gene polymorphism].

OBJECTIVE: To investigate allelic frequency of sulfonylurea receptor-1 (SUR1) in gestational diabetes mellitus (GDM) women of Han nationality in north China in order to find out susceptible gene associated with GDM, and to assess the association between SUR1 allele and body mass index (BMI) and secretion of insulin. METHODS: Seventy cases of pregnant women were selected. It included 35 cases of pregnant women with GDM (GDM group), 35 cases of normal pregnant women (normal control group). Another 35 women patients with type 2 diabetes in the same period as T2DM group. By using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), we detected the distribution of SUR1 alleles frequency in all individuals of three groups. We also examined BMI, fasting insulin (INS(0)) and 2 h insulin levels (INS(120)). RESULTS: There was significantly increased c alleles frequency of SUR1 in GDM and T2DM women compared with normal pregnancy (70.0%, 71.4% and 52.9%, P < 0.05). Also significantly increased A alleles frequency of SUR1 in GDM and T2DM women was found compared with normal pregnancy (41.4%, 44.3% and 24.3%, P < 0.05). In GDM group, women carrying cc genotype had a higher BMI [(29.2 +/- 5.6) kg/m(2)], INS(0) [(14.9 +/- 8.7) mU/L] and INS(120) [(40.2 +/- 12.1) mU/L] as compared with those in carriers of other genotypes (ct and tt) (all P < 0.05). Also they had a lower insulin sensitivity (HOMA-IR) (3.9 +/- 2.5) as compared with carriers of ct genotype. Women carrying AA genotype had a higher INS(0) as compared with carriers of other genotypes (AG and GG) [(15.4 +/- 3.2), (12.1 +/- 4.5) and (11.5 +/- 4.8) mU/L, both P < 0.05]. Logistic regression analysis showed there was relationship between SUR1 cc genotype and severity of GDM (P = 0.005, RR = 25.128). CONCLUSIONS: There are -3t-->c and A/G polymorphism of SUR1 gene in the Han nationality. Alleles c of SUR1 are significantly implicated in the susceptibility to GDM. It suggests that the defect in SUR1 gene (cc and AA) may contribute to insulin hypersecretion, which might be the cause of increased body weight and decreased insulin sensitivity and genotype cc of SUR1 is connected with severe type of GDM. It might be the predictable index of GDM conversion to type 2 diabetes.

Tyrosine dephosphorylation enhances the therapeutic target activity of epidermal growth factor receptor (EGFR) by disrupting its interaction with estrogen receptor (ER).

Protein-protein interactions can increase or decrease its therapeutic target activity and the determining factors involved, however, are largely unknown. Here, we report that tyrosine-dephosphorylation of epidermal growth factor receptor (EGFR) increases its therapeutic target activity by disrupting its interaction with estrogen receptor (ER). Protein tyrosine phosphatase H1 (PTPH1) dephosphorylates the tyrosine kinase EGFR, disrupts its interaction with the nuclear receptor ER, and increases breast cancer sensitivity to small molecule tyrosine kinase inhibitors (TKIs). These effects require PTPH1 catalytic activity and its interaction with EGFR, suggesting that the phosphatase may increase the sensitivity by dephosphorylating EGFR leading to its dissociation with ER. Consistent with this notion, a nuclear-localization defective ER has a higher EGFR-binding activity and confers the resistance to TKI-induced growth inhibition. Additional analysis show that PTPH1 stabilizes EGFR, stimulates the membranous EGFR accumulation, and enhances the growth-inhibitory activity of a combination therapy of TKIs with an anti-estrogen. Since EGFR and ER both are substrates for PTPH1 in vitro and in intact cells, these results indicate that an inhibitory EGFR-ER protein complex can be switched off through a competitive enzyme-substrate binding. Our results would have important implications for the treatment of breast cancer with targeted therapeutics.

Identification of a ternary protein-complex as a therapeutic target for K-Ras-dependent colon cancer.

A cancer phenotype is driven by several proteins and targeting a cluster of functionally interdependent molecules should be more effective for therapeutic intervention. This is specifically important for Ras-dependent cancer, as mutated (MT) Ras is non-druggable and targeting its interaction with effectors may be essential for therapeutic intervention. Here, we report that a protein-complex activated by the Ras effector p38γ MAPK is a novel therapeutic target for K-Ras-dependent colon cancer. Unbiased proteomic screening and immune-precipitation analyses identified p38γ interaction with heat shock protein 90 (Hsp90) and K-Ras in K-Ras MT, but not wild-type (WT), colon cancer cells, indicating a role of this complex in Ras-dependent growth. Further experiments showed that this complex requires p38γ and Hsp90 activity to maintain MT, but not WT, K-Ras protein expression. Additional studies demonstrated that this complex is activated by p38γ-induced Hsp90 phosphorylation at S595, which is important for MT K-Ras stability and for K-Ras dependent growth. Of most important, pharmacologically inhibition of Hsp90 or p38γ activity disrupts the complex, decreases K-Ras expression, and selectively inhibits the growth of K-Ras MT colon cancer in vitro and in vivo. These results demonstrated that the p38γ-activated ternary complex is a novel therapeutic target for K-Ras-dependent colon cancer.

MK2 Regulates Ras Oncogenesis through Stimulating ROS Production.

Ras signals through both mitogenic and stress pathways and studies of Ras regulatory effects of stress pathways hold great promise to control Ras-dependent malignancies. Our previous work showed Ras activation of a stress kinase (MAPK-activated protein kinase 2 [MK2]), and here, we examine regulatory effects of MK2 on Ras oncogenesis. MK2 knockout was shown to increase Ras transformation in mouse embryonic fibroblasts (MEFs) in vitro and to enhance the resultant tumor growth in mice, indicating a tumor suppressor activity. In Ras-dependent and -independent human colon cancer, however, MK2-forced expression increases and MK2 depletion decreases the malignant growth, suggesting its oncogenic activity. The oncogenic activity of MK2 couples with its activation by both stress and mitogenic signals through extracellular signal-regulated kinase and p38α pathways, whereas its tumor-suppressing effect links to its stimulation only by stress downstream of p38α. Of interest, MK2 was shown to decrease intracellular levels of reactive oxygen species (ROS) in MEFs but increase its production in human colon cancer cells, and experiments with antioxidants revealed that ROS is required for Ras oncogenesis in both systems. These results indicate that MK2 can increase or decrease Ras oncogenesis dependent of its ROS regulatory activities.