Targeting of KRAS mutant tumors by HSP90 inhibitors involves degradation of STK33

STK33 as the functional substrate of miR-454-3p for suppression and apoptosis in neuroblastoma

miR-454-3p has been reported to be a tumor suppressive micro-RNA (miRNA) in multiple cancer types. We identified the kinase STK33 mRNA, which is a high-risk factor for survival in neuroblastoma (NB) patients, as being a substrate of miR-454-3p in NB. Even though STK33 is an attractive target for several cancers, development of inhibitors of STK33 has been challenging. For the various cell lines tested, we demonstrated reduced growth and viability with the miR-454-3p mimic. From among the candidate NB-associated miRNAs, miR-454-3p mimic and its antagonist had the most profound effect on STK33 mRNA and protein level changes. Under various conditions of growth and external stress for the cells, the RNA levels for miR-454-3p and STK33 also negatively correlated. Luciferase reporter assays demonstrated STK33 as a substrate for miR-454-3p, and recombinant versions of STK33 resistant to miR-454-3p significantly blunted the suppressive effect of the miR-454-3p and established STK33 as the major functional substrate of miR-454-3p. Overexpression of miR-454-3p or knockdown of STK33 mRNA promoted autophagy, and at the same time, increased the apoptotic markers in the tested NB cells, indicating a mechanism for the suppressive effect of the agents. Given the difficult-to-drug targets such as STK33 and the recent successes in RNA delivery methods for cancer treatment, it is thought that targeting cancer cells with a suppressive miRNA such as miR-454-3p for STK33-dependent cancer types may be an alternative means of NB therapy.

Advances in dual-targeting inhibitors of HDAC6 for cancer treatment

Histone Deacetylase 6 (HDAC6) is an essential regulator of histone acetylation processes, exerting influence on a multitude of cellular functions such as cell motility, endocytosis, autophagy, apoptosis, and protein trafficking through its deacetylation activity. The significant implications of HDAC6 in diseases such as cancer, neurodegenerative disorders, and immune disorders have motivated extensive investigation into the development of specific inhibitors targeting this enzyme for therapeutic purposes. Single targeting drugs carry the risk of inducing drug resistance, thus prompting exploration of dual targeting therapy which offers the potential to impact multiple signaling pathways simultaneously, thereby lowering the likelihood of resistance development. While pharmacological studies have exhibited promise in combined therapy involving HDAC6, challenges related to potential drug interactions exist. In response to these challenges, researchers are investigating HDAC6 hybrid molecules which enable the concomitant targeting of HDAC6 and other key proteins, thus enhancing treatment efficacy while mitigating side effects and reducing the risk of resistance compared to traditional combination therapies. The published design strategies for dual targeting inhibitors of HDAC6 are summarized and discussed in this review. This will provide some valuable insights into more novel HDAC6 dual targeting inhibitors to meet the urgent need for innovative therapies in oncology and other related fields.

Serine/Threonine Kinase (STK) 33 promotes the proliferation and metastasis of human esophageal squamous cell carcinoma via inflammation-related pathway

The serine/threonine kinase (STK) 33 plays a key role in cancer cell proliferation and metastasis. Abnormal STK33 expression is closely related to malignancy of numerous cancers. This study suggests the important role of STK33 in the pathogenesis and metastatic progression of esophageal squamous cell carcinoma (ESCC). STK33 expression in human ESCC tissues was detected by immunohistochemical technique. Further, we analyzed the relationship between STK33 and clinical and pathological factors as well as the prognosis of patients. ECa109 cell line was cultured and transfected with STK33-RNAi lentiviral vector to perform Hochest33342 & PI and metastasis experiments. The TCGA database was used to analyze the STK33 expression level in ESCC. All statistical analyses were performed in SPSS 23.0 software. Differences with P < 0.05 were considered statistically significant. In human ESCC specimens, STK33 was overexpressed and associated with poor prognosis. Silencing STK33 expression suppressed ESCC proliferation, migration, invasion, and tumor growth. STK33 also mediated angiogenesis, TGFβ, and inflammatory response in ESCC. Mechanistic investigations revealed that STK33 regulates ESCC through multiple complex pathways. Dysregulated STK33 signaling promotes ESCC growth and progression. Thus, our findings identified STK33 as a candidate treatment target that improves ESCC therapy.

Identification of KLHDC2 as an efficient proximity-induced degrader of K-RAS, STK33, β-catenin, and FoxP3

Targeted protein degradation (TPD), induced by enforcing target proximity to an E3 ubiquitin ligase using small molecules has become an important drug discovery approach for targeting previously undruggable disease-causing proteins. However, out of over 600 E3 ligases encoded by the human genome, just over 10 E3 ligases are currently utilized for TPD. Here, using the affinity-directed protein missile (AdPROM) system, in which an anti-GFP nanobody was linked to an E3 ligase, we screened over 30 E3 ligases for their ability to degrade 4 target proteins, K-RAS, STK33, β-catenin, and FoxP3, which were endogenously GFP-tagged. Several new E3 ligases, including CUL2 diGly receptor KLHDC2, emerged as effective degraders, suggesting that these E3 ligases can be taken forward for the development of small-molecule degraders, such as proteolysis targeting chimeras (PROTACs). As a proof of concept, we demonstrate that a KLHDC2-recruiting peptide-based PROTAC connected to chloroalkane is capable of degrading HALO-GFP protein in cells.

HSPs/STAT3 Interplay Sustains DDR and Promotes Cytokine Release by Primary Effusion Lymphoma Cells

Primary effusion lymphoma (PEL) is a rare and aggressive B-cell lymphoma, against which current therapies usually fail. In the present study, we show that targeting HSPs, such as HSP27, HSP70 and HSP90, could be an efficient strategy to reduce PEL cell survival, as it induces strong DNA damage, which correlated with an impairment of DDR. Moreover, as HSP27, HSP70 and HSP90 cross talk with STAT3, their inhibition results in STAT3 de-phosphorylation and. On the other hand, the inhibition of STAT3 may downregulate these HSPs. These findings suggest that targeting HSPs has important implications in cancer therapy, as it can reduce the release of cytokines by PEL cells, which, besides affecting their own survival, could negatively influence anti-cancer immune response.

9-ING-41, a Small Molecule Inhibitor of GSK-3β, Potentiates the Effects of Chemotherapy on Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most common and lethal types of cancer. Although researchers have made significant efforts to study the mechanisms underlying CRC drug resistance, our knowledge of this disease is still limited, and novel therapies are in high demand. It is urgent to find new targeted therapy considering limited chemotherapy options. KRAS mutations are the most frequent molecular alterations in CRC. However, there are no approved K-Ras targeted therapies for these tumors yet. GSK-3β is demonstrated to be a critically important kinase for the survival and proliferation of K-Ras–dependent pancreatic cancer cells. In this study, we tested combinations of standard-of-care therapy and 9-ING-41, a small molecule inhibitor of GSK-3β, in CRC cell lines and patient-derived tumor organoid models of CRC. We demonstrate that 9-ING-41 inhibits the growth of CRC cells via a distinct from chemotherapy mechanism of action. Although molecular biomarkers of 9-ING-41 efficacy are yet to be identified, the addition of 9-ING-41 to the standard-of-care drugs 5-FU and oxaliplatin could significantly enhance growth inhibition in certain CRC cells. The results of the transcriptomic analysis support our findings of cell cycle arrest and DNA repair deficiency in 9-ING-41–treated CRC cells. Notably, we find substantial similarity in the changes of the transcriptomic profile after inhibition of GSK-3β and suppression of STK33, another critically important kinase for K-Ras–dependent cells, which could be an interesting point for future research. Overall, the results of this study provide a rationale for the further investigation of GSK-3 inhibitors in combination with standard-of-care treatment of CRC.

Introns control stochastic allele expression bias

Monoallelic expression (MAE) or extreme allele bias can account for incomplete penetrance, missing heritability and non-Mendelian diseases. In cancer, MAE is associated with shorter patient survival times and higher tumor grade. Prior studies showed that stochastic MAE is caused by stochastic epigenetic silencing, in a gene and tissue-specific manner. Here, we used C. elegans to study stochastic MAE in vivo. We found allele bias/MAE to be widespread within C. elegans tissues, presenting as a continuum from fully biallelic to MAE. We discovered that the presence of introns within alleles robustly decreases MAE. We determined that introns control MAE at distinct loci, in distinct cell types, with distinct promoters, and within distinct coding sequences, using a 5'-intron position-dependent mechanism. Bioinformatic analysis showed human intronless genes are significantly enriched for MAE. Our experimental evidence demonstrates a role for introns in regulating MAE, possibly explaining why some mutations within introns result in disease.

Regulation of Mitogen-Activated Protein Kinase Signaling Pathways by the Ubiquitin-Proteasome System and Its Pharmacological Potential

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved signaling pathways that play essential roles in transducing extracellular environmental signals into diverse cellular responses to maintain homeostasis. These pathways are classically organized into an architecture of three sequentially acting protein kinases: a MAPK kinase kinase that phosphorylates and activates a MAPK kinase, which in turn phosphorylates and activates the effector MAPK. The activity of MAPKs is tightly regulated by phosphorylation of their activation loop, which can be modulated by positive and negative feedback mechanisms to control the amplitude and duration of the signal. The signaling outcomes of MAPK pathways are further regulated by interactions of MAPKs with scaffolding and regulatory proteins. Accumulating evidence indicates that, in addition to these mechanisms, MAPK signaling is commonly regulated by ubiquitin-proteasome system (UPS)-mediated control of the stability and abundance of MAPK pathway components. Notably, the biologic activity of some MAPKs appears to be regulated mainly at the level of protein turnover. Recent studies have started to explore the potential of targeted protein degradation as a powerful strategy to investigate the biologic functions of individual MAPK pathway components and as a new therapeutic approach to overcome resistance to current small-molecule kinase inhibitors. Here, we comprehensively review the mechanisms, physiologic importance, and pharmacological potential of UPS-mediated protein degradation in the control of MAPK signaling. SIGNIFICANCE STATEMENT: Accumulating evidence highlights the importance of targeted protein degradation by the ubiquitin-proteasome system in regulating and fine-tuning the signaling output of mitogen-activated protein kinase (MAPK) pathways. Manipulating protein levels of MAPK cascade components may provide a novel approach for the development of selective pharmacological tools and therapeutics.

Sildenafil triggers tumor lethality through altered expression of HSP90 and degradation of PKD2

The repurposing of existing drugs has emerged as an attractive additional strategy to the development of novel compounds in the fight against cancerous diseases. Inhibition of phosphodiesterase 5 (PDE5) has been claimed as a potential approach to target various cancer subtypes in recent years. However, data on the treatment of tumors with PDE5 inhibitors as well as the underlying mechanisms are as yet very scarce. Here, we report that treatment of tumor cells with low concentrations of Sildenafil was associated with decreased cancer cell proliferation and augmented apoptosis in vitro and resulted in impaired tumor growth in vivo. Notably, incubation of cancer cells with Sildenafil was associated with altered expression of HSP90 chaperone followed by degradation of protein kinase D2, a client protein previously reported to be involved in tumor growth. Furthermore, the involvement of low doses of PU-H71, an HSP90 inhibitor currently under clinical evaluation, in combination with low concentrations of Sildenafil, synergistically and negatively impacted on the viability of cancer cells in vivo. Taken together, our study suggests that repurposing of already approved drugs, alone or in combination with oncology-dedicated compounds, may represent a novel cancer therapeutic strategy.

Transcriptional Enhancer Factor Domain Family member 4 Exerts an Oncogenic Role in Hepatocellular Carcinoma by Hippo-Independent Regulation of Heat Shock Protein 70 Family Members

Transcriptional enhancer factor domain family member 4 (TEAD4) is a downstream effector of the conserved Hippo signaling pathway, regulating the expression of genes involved in cell proliferation and differentiation. It is up-regulated in several cancer types and is associated with metastasis and poor prognosis. However, its role in hepatocellular carcinoma (HCC) remains largely unexplored. Using data from The Cancer Genome Atlas, we found that TEAD4 was overexpressed in HCC and was associated with aggressive HCC features and worse outcome. Overexpression of TEAD4 significantly increased proliferation and migration rates in HCC cells in vitro as well as tumor growth in vivo. Additionally, RNA sequencing analysis of TEAD4-overexpressing HCC cells demonstrated that TEAD4 overexpression was associated with the up-regulation of genes involved in epithelial-to-mesenchymal transition, proliferation, and protein-folding pathways. Among the most up-regulated genes following TEAD4 overexpression were the 70-kDa heat shock protein (HSP70) family members HSPA6 and HSPA1A. Chromatin immunoprecipitation-quantitative real-time polymerase chain reaction experiments demonstrated that TEAD4 regulates HSPA6 and HSPA1A expression by directly binding to their promoter and enhancer regions. The pharmacologic inhibition of HSP70 expression in TEAD4-overexpressing cells reduced the effect of TEAD4 on cell proliferation. Finally, by overexpressing TEAD4 in yes-associated protein (YAP)/transcriptional coactivator with PDZ binding motif (TAZ)-knockdown HCC cells, we showed that the effect of TEAD4 on cell proliferation and its regulation of HSP70 expression does not require YAP and TAZ, the main effectors of the Hippo signaling pathway. Conclusion: A novel Hippo-independent mechanism for TEAD4 promotes cell proliferation and tumor growth in HCC by directly regulating HSP70 family members.

Functional proteomic analysis reveals that fungal immunomodulatory protein reduced expressions of heat shock proteins correlates to apoptosis in lung cancer cells

BACKGROUND

Ling Zhi-8 (LZ-8) and GMI are two fungal immunomodulatory proteins (FIPs) with a similar structure and amino acid sequence and are respectively obtained from the medicinal mushroom Ganoderma lucidum and Ganoderma microsporum. They present the anti-cancer progression and metastasis. We previously demonstrated that LZ-8 reduces the tumor progression in lung cancer LLC1 cell-bearing mouse. However, it is unclear whether these FIPs induce changes in the protein expression profile in cancer cells and the mechanism for such a process is not defined.

PURPOSE

This study determines the changes in the proteomic profile for tumor lesions of LLC1 cell-bearing mouse received with LZ-8 and the potential mechanism for FIPs in anti-lung cancer cells.

METHODS

The proteomic profile of tumor lesions was determined using two-dimensional electrophoresis and a LTQ-OrbitrapXL mass spectrometer (LC-MS/MS). The biological processes and the signaling pathway enrichment analysis were performed using Ingenuity Pathway Analysis (IPA). The differentially expressed proteins were verified by Western blot. Cell viability was determined by MTT assay. Cell morphology was characterized using electron microscopy. Migration was detected using the Transwell assay. The apoptotic response was determined using Western blot and flow cytometry.

RESULTS

Obtained results showed that 21 proteins in the tumor lesions exhibited differential (2-fold change, p < 0.05) expression between PBS and LZ-8 treatment groups. LZ-8-induced changes in the proteomic profile that may relate to protein degradation pathways. Specifically, three heat shock proteins (HSPs), HSP60, 70 and 90, were significantly downregulated in tumor lesions of LLC1-bearing mouse received with LZ-8. Both LZ-8 and GMI reduced the protein levels for these HSPs in lung cancer cells. Functional studies showed that they inhibited cell migration but effectively induced apoptotic response in LLC1 cells in vitro. In addition, the inhibitors of HSP60 and HSP70 effectively inhibited cell migration and decreased cell viability of LLC1 cells.

CONCLUSIONS

LZ-8 induced changes in the proteomic profile of tumor lesions which may regulate the HSPs-related cell viability. Moreover, inhibition of HSPs may be related to the anti-lung cancer activity.

Recent developments in targeting genes and pathways by RNAi-based approaches in colorectal cancer

A wide spectrum of genetic and epigenetic variations together with environmental factors has made colorectal cancer (CRC), which involves the colon and rectum, a challenging and heterogeneous cancer. CRC cannot be effectively overcomed by common conventional therapies including surgery, chemotherapy, targeted therapy, and hormone replacement which highlights the need for a rational design of novel anticancer therapy. Accumulating evidence indicates that RNA interference (RNAi) could be an important avenue to generate great therapeutic efficacy for CRC by targeting genes that are responsible for the viability, cell cycle, proliferation, apoptosis, differentiation, metastasis, and invasion of CRC cells. In this review, we underline the documented benefits of small interfering RNAs and short hairpin RNAs to target genes and signaling pathways related to CRC tumorigenesis. We address the synergistic effects of RNAi-mediated gene knockdown and inhibitors/chemotherapy agents to increase the sensitivity of CRC cells to common therapies. Finally, this review points new delivery systems/materials for improving the cellular uptake efficiency and reducing off-target effects of RNAi.

Prodigiosin/PU-H71 as a novel potential combined therapy for triple negative breast cancer (TNBC): preclinical insights

Prodigiosin, a secondary metabolite red pigment produced by Serratia marcescens, has an interesting apoptotic efficacy against cancer cell lines with low or no toxicity on normal cells. HSP90α is known as a crucial and multimodal target in the treatment of TNBC. Our research attempts to assess the therapeutic potential of prodigiosin/PU-H71 combination on MDA-MB-231 cell line. The transcription and protein expression levels of different signalling pathways were assessed. Treatment of TNBC cells with both drugs resulted in a decrease of the number of adherent cells with apoptotic effects. Prodigiosin/PU-H71 combination increased the levels of caspases 3,8 and 9 and decreased the levels of mTOR expression. Additionally, there was a remarkable decrease of HSP90α transcription and expression levels upon treatment with combined therapy. Also, EGFR and VEGF expression levels decreased. This is the first study to show that prodigiosin/PU-H71 combination had potent cytotoxicity on MDA-MB-231 cells; proving to play a paramount role in interfering with key signalling pathways in TNBC. Interestingly, prodigiosin might be a potential anticancer agent to increase the sensitivity of TNBC cells to apoptosis. This study provides a new basis for upcoming studies to overcome drug resistance in TNBC cells.

A Driver Never Works Alone-Interplay Networks of Mutant p53, MYC, RAS, and Other Universal Oncogenic Drivers in Human Cancer

The knowledge accumulating on the occurrence and mechanisms of the activation of oncogenes in human neoplasia necessitates an increasingly detailed understanding of their systemic interactions. None of the known oncogenic drivers work in isolation from the other oncogenic pathways. The cooperation between these pathways is an indispensable element of a multistep carcinogenesis, which apart from inactivation of tumor suppressors, always includes the activation of two or more proto-oncogenes. In this review we focus on representative examples of the interaction of major oncogenic drivers with one another. The drivers are selected according to the following criteria: (1) the highest frequency of known activation in human neoplasia (by mutations or otherwise), (2) activation in a wide range of neoplasia types (universality) and (3) as a part of a distinguishable pathway, (4) being a known cause of phenotypic addiction of neoplastic cells and thus a promising therapeutic target. Each of these universal oncogenic factors—mutant p53, KRAS and CMYC proteins, telomerase ribonucleoprotein, proteasome machinery, HSP molecular chaperones, NF-κB and WNT pathways, AP-1 and YAP/TAZ transcription factors and non-coding RNAs—has a vast network of molecular interrelations and common partners. Understanding this network allows for the hunt for novel therapeutic targets and protocols to counteract drug resistance in a clinical neoplasia treatment.

Inhibition of Heat Shock Protein 90 as a Novel Platform for the Treatment of Cancer

Heat shock protein 90 (Hsp90) plays an essential role in various physiological and pathological processes. It activates client proteins to participate in tumor progression. Blocking Hsp90 could enable effective antitumor effects in many tumor types, such as multiple myeloma and colon cancer. Recently, it has motivated an interest in Hsp90 inhibitors that bind to the N-terminal or C-terminal ATP pocket as antitumor drugs. We reviewed the data from experimental and clinical trials on Hsp90 inhibitors in the treatment of different malignancies to explore and summarize their antitumor mechanisms.

TRPC3 Regulates the Proliferation and Apoptosis Resistance of Triple Negative Breast Cancer Cells through the TRPC3/RASA4/MAPK Pathway

Currently, there is no effective molecular-based therapy for triple-negative breast cancer (TNBC). Canonical transient receptor potential isoform 3 (TRPC3) was previously shown to be upregulated in breast cancer biopsy tissues when compared to normal breast tissues. However, the biological role of TRPC3 in breast cancer still remains to be elucidated. In this study, subcellular fractionation followed by Western blot and immunocytochemistry showed that TRPC3 was over-expressed on the plasma membrane of TNBC line MDA-MB-231 when compared to an estrogen receptor-positive cell line MCF-7. TRPC3 blocker Pyr3 and dominant negative of TRPC3 attenuated proliferation, induced apoptosis and sensitized cell death to chemotherapeutic agents in MDA-MB-231 as measured by proliferation assays. Interestingly, Ras GTPase-activating protein 4 (RASA4), a Ca²⁺-promoted Ras-MAPK pathway suppressor, was found to be located on the plasma membrane of MDA-MB-231. Blocking TRPC3 decreased the amount of RASA4 located on the plasma membrane, with concomitant activation of MAPK pathways. Our results suggest that, in TNBC MDA-MB-231 cells, Ca²⁺ influx through TRPC3 channel sustains the presence of RASA4 on the plasma membrane where it inhibits the Ras-MAPK pathway, leading to proliferation and apoptosis resistance. Our study reveals the novel TRPC3-RASA4-MAPK signaling cascade in TNBC cells and suggests that TRPC3 may be exploited as a potential therapeutic target for TNBC.

Physical plasma-triggered ROS induces tumor cell death upon cleavage of HSP90 chaperone

HSP90 is a ubiquitously expressed molecular chaperone implicated in the correct folding and maturation of a plethora of proteins including protein kinases and transcription factors. While disruption of chaperone activity was associated with augmented cancer cell death and decreased tumor growth both in vitro and in vivo, the regulation of HSP90 is not clearly understood. Here we report that treatment of cancer cells with cold physical plasma, an emerging and less aggressive tumor therapy, resulted in ROS generation which subsequently triggered the cleavage of HSP90. Notably, cleavage of HSP90 was followed by the degradation of PKD2, a crucial regulator of tumor growth and angiogenesis. Pre-sensitization of cancer cells with subliminal doses of PU-H71, an HSP90 inhibitor currently under clinical evaluation, followed by treatment with cold-plasma, synergistically and negatively impacted on the viability of cancer cells. Taken together, cold-plasma can be used in conjunction with pharmacologic treatment in order to target the expression and activity of HSP90 and the downstream client proteins implicated in various cancer cell capabilities.

Combination therapies with HSP90 inhibitors against colorectal cancer

Oncogene stability and homeostasis mediated by the HSP90 chaperone is a crucial protection trait of cancer cells. Therefore, HSP90 represents an attractive therapeutic target for many cancers, including colorectal cancer. Although monotherapy has limited clinical efficacy, preclinical and early-phase clinical studies indicate improved antitumor activity when HSP90 inhibitors are combined with chemotherapies or targeted agents. This may be further improved with a biomarker-guided approach based on oncogenic HSP90 clients, or stratification based on the consensus molecular subtypes of colorectal cancer, suggesting a synergistic activity with 5-fluorouracil in preclinical models of the chemorefractory mesenchymal subtype. Furthermore, HSP90 inhibition may activate mechanisms to turn non-immunogenic tumors hot and improve their recognition by the immune system, suggesting synergy with immune checkpoint blockade.

Simvastatin functions as a heat shock protein 90 inhibitor against triple-negative breast cancer

Acetylation plays an important role in regulating the chaperone activity of heat shock protein 90 (Hsp90) during malignant transformation through the stabilization and conformational maturation of oncogenic proteins. However, the functional acetylation sites, potential anticancer drug targets, are still emerging. We found that acetylation at K292 in Hsp90α is critical for the development and treatment of breast cancer. Acetylation at K292 not only augments the affinity of Hsp90 to ATP, cochaperones, and client proteins but it also promotes cancer cell colony formation, migration, and invasion in vitro as well as tumor growth in vivo. Importantly, K292‐acetylated Hsp90 has been validated as an exciting anticancer drug target by interfering with the complex formation between K292‐acetylated Hsp90 and cochaperone Cdc37, leading to diminishment of kinase client maturation and proteasome‐dependent degradation of kinase substrates. Furthermore, we showed that simvastatin prevented, whereas LBH589 promoted, the progression of Hsp90 chaperone cycling and client maturation, resulting in an increment of cell apoptosis by the combination of simvastatin and LBH589 in a mouse xenograft model. These data suggest that simvastatin is a novel Hsp90 inhibitor to disrupt the formation of the K292‐acetylated Hsp90/Cdc37 complex in triple‐negative breast cancer cells. The combination of simvastatin with LBH589 could be used as a novel therapeutic strategy for triple‐negative breast cancer.

Synthetic Lethal Vulnerabilities in KRAS-Mutant Cancers

KRAS is the most commonly mutated oncogene in human cancer. Most KRAS-mutant cancers depend on sustained expression and signaling of KRAS, thus making it a high-priority therapeutic target. Unfortunately, development of direct small molecule inhibitors of KRAS function has been challenging. An alternative therapeutic strategy for KRAS-mutant malignancies involves targeting codependent vulnerabilities or synthetic lethal partners that are preferentially essential in the setting of oncogenic KRAS. KRAS activates numerous effector pathways that mediate proliferation and survival signals. Moreover, cancer cells must cope with substantial oncogenic stress conferred by mutant KRAS. These oncogenic signaling pathways and compensatory coping mechanisms of KRAS-mutant cancer cells form the basis for synthetic lethal interactions. Here, we review the compendium of previously identified codependencies in KRAS-mutant cancers, including the results of numerous functional genetic screens aimed at identifying KRAS synthetic lethal targets. Importantly, many of these vulnerabilities may represent tractable therapeutic opportunities.

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.

A Novel Inducible Mouse Model of MLL-ENL-driven Mixed-lineage Acute Leukemia

Supplemental Digital Content is available in the text

Previous retroviral and knock-in approaches to model human t(11;19)⁺ acute mixed-lineage leukemia in mice resulted in myeloproliferation and acute myeloid leukemia not fully recapitulating the human disease. The authors established a doxycycline (DOX)-inducible transgenic mouse model “iMLL-ENL” in which induction in long-term hematopoietic stem cells, lymphoid primed multipotent progenitor cells, multipotent progenitors (MPP4) but not in more committed myeloid granulocyte-macrophage progenitors led to a fully reversible acute leukemia expressing myeloid and B-cell markers. iMLL-ENL leukemic cells generally expressed lower MLL-ENL mRNA than those obtained after retroviral transduction. Disease induction was associated with iMLL-ENL levels exceeding the endogenous Mll1 at mRNA and protein levels. In leukemic cells from t(11;19)⁺ leukemia patients, MLL-ENL mRNA also exceeded the endogenous MLL1 levels suggesting a critical threshold for transformation. Expression profiling of iMLL-ENL acute leukemia revealed gene signatures that segregated t(11;19)⁺ leukemia patients from those without an MLL translocation. Importantly, B220⁺iMLL-ENL leukemic cells showed a higher in vivo leukemia initiation potential than coexisting B220⁻ cells. Collectively, characterization of a novel transgenic mouse model indicates that the cell-of-origin and the fusion gene expression levels are both critical determinants for MLL-ENL-driven acute leukemia.

Prospective identification of resistance mechanisms to HSP90 inhibition in KRAS mutant cancer cells

Inhibition of the HSP90 chaperone results in depletion of many signaling proteins that drive tumorigenesis, such as downstream effectors of KRAS, the most commonly mutated human oncogene. As a consequence, several small-molecule HSP90 inhibitors are being evaluated in clinical trials as anticancer agents. To prospectively identify mechanisms through which HSP90-dependent cancer cells evade pharmacologic HSP90 blockade, we generated multiple mutant KRAS-driven cancer cell lines with acquired resistance to the purine-scaffold HSP90 inhibitor PU-H71. All cell lines retained dependence on HSP90 function, as evidenced by sensitivity to short hairpin RNA-mediated suppression of HSP90AA1 or HSP90AB1 (also called HSP90α and HSP90β, respectively), and exhibited two types of genomic alterations that interfere with the effects of PU-H71 on cell viability and proliferation: (i) a Y142N missense mutation in the ATP-binding domain of HSP90α that co-occurred with amplification of the HSP90AA1 locus, (ii) genomic amplification and overexpression of the ABCB1 gene encoding the MDR1 drug efflux pump. In support of a functional role for these alterations, exogenous expression of HSP90α Y142N conferred PU-H71 resistance to HSP90-dependent cells, and pharmacologic MDR1 inhibition with tariquidar or lowering ABCB1 expression restored sensitivity to PU-H71 in ABCB1-amplified cells. Finally, comparison with structurally distinct HSP90 inhibitors currently in clinical development revealed that PU-H71 resistance could be overcome, in part, by ganetespib (also known as STA9090) but not tanespimycin (also known as 17-AAG). Together, these data identify potential mechanisms of acquired resistance to small molecules targeting HSP90 that may warrant proactive screening for additional HSP90 inhibitors or rational combination therapies.

Krüppel-like Factor 4 Suppresses Serine/Threonine Kinase 33 Activation and Metastasis of Gastric Cancer through Reversing Epithelial-Mesenchymal Transition

Background: Cancers with aberrant expression of Serine/threonine kinase 33 (STK33) has been reported to be particularly aggressive. However, its expression, clinical significance, and biological functions in gastric cancer remain largely unknown. In the present study, we determined the expression and function of STK33 in gastric cancer and delineated the clinical significance of the Krüppel-like factor 4 (KLF4)/STK33 signaling pathway.Methods: STK33 expression and its association with multiple clinicopathologic characteristics were analyzed immunohistochemically in human gastric cancer specimens. STK33 knockdown and overexpression were used to dissect the underlying mechanism of its functions in gastric cancer cells. Regulation and underlying mechanisms of STK33 expression by KLF4 in gastric cancer cells were studied using cell and molecular biological methods.Results: Drastically higher expression of STK33 was observed in gastric cancer and gastric intraepithelial neoplasia tissues compared with adjacent normal gastric tissues. Increased STK33 expression correlated directly with tumor size, lymph node, and distant metastasis; and patients with low STK33 expression gastric cancer were predicted to have a favorable prognosis. Enforced expression of STK33 promoted gastric cancer cell proliferation, migration, and invasion in vitro and in vivo, whereas reduced STK33 did the opposite. Moreover, STK33 promoted epithelial-mesenchymal transition (EMT) in vitro Mechanistically, KLF4 transcriptionally inhibited STK33 expression in gastric cancer cells. KLF4-mediated inhibition of gastric cancer cell invasion was reversed by upregulation of STK33 expression.Conclusions: STK33 has pro-tumor function and is a critical downstream mediator of KLF4 in gastric cancer. STK33 may serve as a potential prognostic marker and therapeutic target for gastric cancer. Clin Cancer Res; 24(10); 2440-51. ©2018 AACR.

STK33 Promotes Growth and Progression of Pancreatic Cancer as a Critical Downstream Mediator of HIF1α

The serine/threonine kinase STK33 has been implicated in cancer cell proliferation. Here, we provide evidence of a critical role for STK33 in the pathogenesis and metastatic progression of pancreatic ductal adenocarcinoma (PDAC). STK33 expression in PDAC was regulated by the hypoxia-inducible transcription factor HIF1α. In human PDAC specimens, STK33 was overexpressed and associated with poor prognosis. Enforced STK33 expression promoted PDAC proliferation, migration, invasion, and tumor growth, whereas STK33 depletion exerted opposing effects. Mechanistic investigations showed that HIF1α regulated STK33 via direct binding to a hypoxia response element in its promoter. In showing that dysregulated HIF1α/STK33 signaling promotes PDAC growth and progression, our results suggest STK33 as a candidate therapeutic target to improve PDAC treatment. Cancer Res; 77(24); 6851-62. ©2017 AACR.

STK33 participates to HSP90-supported angiogenic program in hypoxic tumors by regulating HIF-1α/VEGF signaling pathway

Lately, the HSP90 client serine/threonine kinase STK33 emerged to be required by cancer cells for their viability and proliferation. However, its mechanistic contribution to carcinogenesis is not clearly understood. Here we report that elevated STK33 expression correlates with advanced stages of human pancreatic and colorectal carcinomas. Impaired proliferation and augmented apoptosis associated with genetic abrogation of STK33 were paralleled by decreased vascularization in tumor xenografts. In line with this, ectopic STK33 not only promoted tumor growth after pharmacologic inhibition of HSP90 using structurally divergent small molecules currently in clinical development, but also restored blood vessel formation in vivo. Mechanistic studies demonstrated that HSP90-stabilized STK33 interacts with and regulates hypoxia-driven accumulation and activation of HIF-1α as well as secretion of VEGF-A in hypoxic cancer cells. In addition, our study reveals a putative cooperation between STK33 and other HSP90 client protein kinases involved in molecular and cellular events through which cancer cells ensure their survival by securing the oxygen and nutrient supply. Altogether, our findings indicate that STK33 interferes with signals from hypoxia and HSP90 to promote tumor angiogenesis and tumor growth.

Correlation between STK33 and the pathology and prognosis of lung cancer

Correlation between the expression of STK33 and the pathology of lung cancer was investigated, to explore its effects on prognosis. Hundred and two lung cancer patients diagnosed by pathological examinations were randomly selected in Shanghai Jiao Tong University Affiliated Sixth People's Hospital from February, 2012 to February, 2017 to serve as observation group, and the tumor tissues were collected. At the same time, 19 patients with lung benign lesions were selected and lung tissues were also collected to serve as control group. RT-qPCR was used to detect the expression of STK33 mRNA in tissues. Expression levels of STK33 protein were detected and compared by SP immunohistochemistry staining and western blot analysis. Statistical analysis was performed to analyze the correlation between STK33 expression and the pathology and prognosis of lung cancer. Results of PCR showed that expression level of STK33 gene in control group was significantly lower than that in observation group (p<0.05). The expression level of STK33 mRNA in lung adenocarcinoma and squamous cell carcinoma was lower than that in lung small cell carcinoma and large cell carcinoma (p<0.05). Western blot analysis showed that the expression level of STK33 protein in lung small cell carcinoma and large cell carcinoma was significantly higher than that in lung adenocarcinoma and squamous cell carcinoma (p<0.05). Immunohistochemistry staining showed that the positive rate of STK33 in lung large cell carcinoma (100%) and small cell carcinoma (100%) was significantly higher than that in lung adenocarcinoma (88.1%) and squamous cell carcinoma (86.2%) (p<0.05). The 5-year survival rate analysis showed that the recurrence-free survival rate and overall survival rate of STK33 gene high expression level group were significantly lower than those of low expression level group (p<0.05). The differential expression level of STK33 is related to the pathology and prognosis of lung cancer, which is of great value in clinical diagnosis and prognosis evaluation.

Musashi-1 promotes a cancer stem cell lineage and chemoresistance in colorectal cancer cells

Colorectal cancers (CRCs) are a critical health issue worldwide. Cancer stem cell (CSC) lineages are associated with tumour transformation, progression, and malignant transformation. However, how lineages are transformed and how chemoresistance is acquired by CRCs remain largely unknown. In this report, we demonstrated that the RNA-binding protein Musashi-1 enhanced the development of CD44⁺ colorectal CSCs and triggered the formation of anti-apoptotic stress granules (SGs). Our results indicated that CD44⁺ CSC lineage-specific induction of tumour malignancies was controlled by Musashi-1. In addition, Musashi-1 formed SGs when CRC cell lines were treated with 5-fluorouracil. The C-terminal domain of Musashi-1 was critical for recruitment of Musashi-1 into SGs. Intracellular Musashi-1 SGs enhanced the chemoresistance of CRCs. Analysis of clinical CRC samples indicated that Musashi-1 expression was prominent in CRC stage IIA and IIB. In summary, we demonstrated that Musashi-1, a stemness gene, is a critical modulator that promotes the development of CD44⁺ colorectal CSCs and also enhances CRC chemoresistance via formation of SGs. Our findings elucidated a novel mechanism of CRC chemoresistance through increased anti-apoptotic effects via Musashi-1-associated SGs.

Re-examining HSPC1 inhibitors

HSPC1 is a critical protein in cancer development and progression, including colorectal cancer (CRC). However, clinical trial data reporting the effectiveness of HSPC1 inhibitors on several cancer types has not been as successful as predicted. Furthermore, some N-terminal inhibitors appear to be much more successful than others despite similar underlying mechanisms. This study involved the application of three N-terminal HSPC1 inhibitors, 17-DMAG, NVP-AUY922 and NVP-HSP990 on CRC cells. The effects on client protein levels over time were examined. HSPC1 inhibitors were also applied in combination with chemotherapeutic agents commonly used in CRC treatment (5-fluorouracil, oxaliplatin and irinotecan). As HSPA1A and HSPB1 have anti-apoptotic activity, gene-silencing techniques were employed to investigate the significance of these proteins in HSPC1 inhibitor and chemotherapeutic agent resistance. When comparing the action of the three HSPC1 inhibitors, there are distinct differences in the time course of important client protein degradation events. The differences between HSPC1 inhibitors were also reflected in combination treatment-17-DMAG was more effective compared with NVP-AUY922 in potentiating the cytotoxic effects of 5-fluorouracil, oxaliplatin and irinotecan. This study concludes that there are distinct differences between N-terminal HSPC1 inhibitors, despite their common mode of action. Although treatment with each of the inhibitors results in significant induction of the anti-apoptotic proteins HSPA1A and HSPB1, sensitivity to HSPC1 inhibitors is not improved by gene silencing of HSPA1A or HSPB1. HSPC1 inhibitors potentiate the cytotoxic effects of chemotherapeutic agents in CRC, and this approach is readily available to enter clinical trials. From a translational point of view, there may be great variability in sensitivity to the inhibitors between individual patients.

Targeting Fibroblast Growth Factor Receptor 1 for Treatment of Soft-Tissue Sarcoma

Purpose: Altered FGFR1 signaling has emerged as a therapeutic target in epithelial malignancies. In contrast, the role of FGFR1 in soft-tissue sarcoma (STS) has not been established. Prompted by the detection and subsequent therapeutic inhibition of amplified FGFR1 in a patient with metastatic leiomyosarcoma, we investigated the oncogenic properties of FGFR1 and its potential as a drug target in patients with STS.Experimental Design: The frequency of FGFR1 amplification and overexpression, as assessed by FISH, microarray-based comparative genomic hybridization and mRNA expression profiling, SNP array profiling, and RNA sequencing, was determined in three patient cohorts. The sensitivity of STS cell lines with or without FGFR1 alterations to genetic and pharmacologic FGFR1 inhibition and the signaling pathways engaged by FGFR1 were investigated using viability assays, colony formation assays, and biochemical analysis.Results: Increased FGFR1 copy number was detected in 74 of 190 (38.9%; cohort 1), 13 of 79 (16.5%; cohort 2), and 80 of 254 (31.5%; cohort 3) patients. FGFR1 overexpression occurred in 16 of 79 (20.2%, cohort 2) and 39 of 254 (15.4%; cohort 3) patients. Targeting of FGFR1 by RNA interference and small-molecule inhibitors (PD173074, AZD4547, BGJ398) revealed that the requirement for FGFR1 signaling in STS cells is dictated by FGFR1 expression levels, and identified the MAPK-ERK1/2 axis as critical FGFR1 effector pathway.Conclusions: These data identify FGFR1 as a driver gene in multiple STS subtypes and support FGFR1 inhibition, guided by patient selection according to the FGFR1 expression and monitoring of MAPK-ERK1/2 signaling, as a therapeutic option in this challenging group of diseases. Clin Cancer Res; 23(4); 962-73. ©2016 AACR.

A Chemogenomic Screening Platform Used to Identify Chemotypes Perturbing HSP90 Pathways

Compounds that modulate the heat shock protein (HSP) network have potential in a broad range of research applications and diseases. A yeast-based liquid culture assay that measured time-dependent turbidity enabled the high-throughput screening of different Saccharomyces cerevisae strains to identify HSP modulators with unique molecular mechanisms. A focused set of four strains, with differing sensitivities to Hsp90 inhibitors, was used to screen a compound library of 3680 compounds. Computed turbidity curve functions were used to classify strain responses and sensitivity to chemical effects across the compound library. Filtering based on single-strain selectivity identified nine compounds as potential heat shock modulators, including the known Hsp90 inhibitor macbecin. Haploid yeast deletion strains (360), mined from previous Hsp90 inhibitor yeast screens and heat shock protein interaction data, were screened for differential sensitivities to known N-terminal ATP site-directed Hsp90 inhibitors to reveal functional distinctions. Strains demonstrating differential sensitivity (13) to Hsp90 inhibitors were used to prioritize primary screen hit compounds, with NSC145366 emerging as the lead hit. Our follow-up biochemical and functional studies show that NSC145366 directly interacts and inhibits the C-terminus of Hsp90, validating the platform as a powerful approach for early-stage identification of bioactive modulators of heat shock-dependent pathways.

Defeat mutant KRAS with synthetic lethality

Ras proteins are considered as the founding members of a large superfamily of small GTPases that control fundamental cellular functions. Mutationally activated RAS genes were discovered in human cancer cells more than 3 decades ago, but intensive efforts on Ras structure, biochemistry, function and signaling continue even now. Because mutant Ras proteins are inherently difficult to inhibit and have yet been therapeutically conquered, it was designated as “the Everest of oncogenes” in the cancer genome landscape, further promoting a “renaissance” in RAS research. Different paths to directly or indirectly targeting mutant Ras signaling are currently under investigation in the hope of finding an efficacious regimen. Inhibitors directly binding to KRAS^G12C to block its downstream signaling have been revealed, supporting the notion of Ras' druggability. An alternative indirect approach by targeting synthetic lethal interactors of mutant RAS is underway. We recently employed a synthetic lethal drug screen plus a combinatorial strategy using a panel of clinical agents and discovered that KRAS-mutant cancers were fragile to the combined inhibition of polo-like kinase 1 (Plk1) and RhoA/Rho kinase (ROCK). The combined regimen of BI-2536 (a Plk1 inhibitor) and fasudil (a ROCK inhibitor) promoted a significant inhibition of patient-derived lung cancer xenografts and prolonged the survival of LSL-KRAS^G12D mice. In this commentary, we will summarize the state-of-the art for the direction of synthetic lethality, and also speculate on the future development of this approach.

Suppression of KRas-mutant cancer through the combined inhibition of KRAS with PLK1 and ROCK

No effective targeted therapies exist for cancers with somatic KRAS mutations. Here we develop a synthetic lethal chemical screen in isogenic KRAS-mutant and wild-type cells to identify clinical drug pairs. Our results show that dual inhibition of polo-like kinase 1 and RhoA/Rho kinase (ROCK) leads to the synergistic effects in KRAS-mutant cancers. Microarray analysis reveals that this combinatory inhibition significantly increases transcription and activity of cyclin-dependent kinase inhibitor p21(WAF1/CIP1), leading to specific G2/M phase blockade in KRAS-mutant cells. Overexpression of p21(WAF1/CIP1), either by cDNA transfection or clinical drugs, preferentially impairs the growth of KRAS-mutant cells, suggesting a druggable synthetic lethal interaction between KRAS and p21(WAF1/CIP1). Co-administration of BI-2536 and fasudil either in the LSL-KRAS(G12D) mouse model or in a patient tumour explant mouse model of KRAS-mutant lung cancer suppresses tumour growth and significantly prolongs mouse survival, suggesting a strong synergy in vivo and a potential avenue for therapeutic treatment of KRAS-mutant cancers.

Contextualizing the Genes Altered in Bladder Neoplasms in Pediatric andTeen Patients Allows Identifying Two Main Classes of Biological ProcessesInvolved and New Potential Therapeutic Targets

Research on bladder neoplasms in pediatric and teen patients (BNPTP) has described 21 genes, which are variously involved in this disease and are mostly responsible for deregulated cell proliferation. However, due to the limited number of publications on this subject, it is still unclear what type of relationships there are among these genes and which are the chances that, while having different molecular functions, they i) act as downstream effector genes of well-known pro- or anti- proliferative stimuli and/or interplay with biochemical pathways having oncological relevance or ii) are specific and, possibly, early biomarkers of these pathologies. A Gene Ontology (GO)-based analysis showed that these 21 genes are involved in biological processes, which can be split into two main classes: cell regulation-based and differentiation/development-based. In order to understand the involvement/overlapping with main cancer-related pathways, we performed a meta-analysis dependent on the 189 oncogenic signatures of the Molecular Signatures Database (OSMSD) curated by the Broad Institute. We generated a binary matrix with 53 gene signatures having at least one hit; this analysis i) suggests that some genes of the original list show inconsistencies and might need to be experimentally re- assessed or evaluated as biomarkers (in particular, ACTA2) and ii) allows hypothesizing that important (proto)oncogenes (E2F3, ERBB2/HER2, CCND1, WNT1, and YAP1) and (putative) tumor suppressors (BRCA1, RBBP8/CTIP, and RB1-RBL2/p130) may participate in the onset of this disease or worsen the observed phenotype, thus expanding the list of possible molecular targets for the treatment of BNPTP.

Inhibition of HSP90 by AUY922 Preferentially Kills Mutant KRAS Colon Cancer Cells by Activating Bim through ER Stress

Oncogenic mutations of KRAS pose a great challenge in the treatment of colorectal cancer. Here we report that mutant KRAS colon cancer cells are nevertheless more susceptible to apoptosis induced by the HSP90 inhibitor AUY922 than those carrying wild-type KRAS. Although AUY922 inhibited HSP90 activity with comparable potency in colon cancer cells irrespective of their KRAS mutational statuses, those with mutant KRAS were markedly more sensitive to AUY922-induced apoptosis. This was associated with upregulation of the BH3-only proteins Bim, Bik, and PUMA. However, only Bim appeared essential, in that knockdown of Bim abolished, whereas knockdown of Bik or PUMA only moderately attenuated apoptosis induced by AUY922. Mechanistic investigations revealed that endoplasmic reticulum (ER) stress was responsible for AUY922-induced upregulation of Bim, which was inhibited by a chemical chaperone or overexpression of GRP78. Conversely, siRNA knockdown of GRP78 or XBP-1 enhanced AUY922-induced apoptosis. Remarkably, AUY922 inhibited the growth of mutant KRAS colon cancer xenografts through activation of Bim that was similarly associated with ER stress. Taken together, these results suggest that AUY922 is a promising drug in the treatment of mutant KRAS colon cancers, and the agents that enhance the apoptosis-inducing potential of Bim may be useful to improve the therapeutic efficacy.

STK33 promotes hepatocellular carcinoma through binding to c-Myc

OBJECTIVE

STK33 has been reported to play an important role in cancer cell proliferation. We investigated the role of STK33 in hepatocellular carcinoma (HCC) and its underlying mechanisms.

DESIGN

251 patients with HCC were analysed for association between STK33 expression and clinical stage and survival rate. Tamoxifen (TAM)-inducible, hepatocyte-specific STK33 transgenic and knockout mice models were used to study the role of STK33 in liver tumorigenesis. HCC cell lines were used to study the role of STK33 in cell proliferation in vitro and in vivo.

RESULTS

STK33 expression was found to be frequently upregulated in patients with HCC. Significant associations were found between increased expression of STK33 and advanced HCC staging and shorter disease-free survival of patients. Overexpression of STK33 increased HCC cell proliferation both in vitro and in vivo, whereas suppression of STK33 inhibited this effect. Using a TAM-inducible, hepatocyte-specific STK33 transgenic mouse model, we found that overexpression of STK33 resulted in increased hepatocyte proliferation, leading to tumour cell burst. Using a TAM-inducible, hepatocyte-specific STK33 knockout mouse model, we found that, when subjected to the diethylnitrosamine (DEN) liver cancer bioassay, STK33KO(flox/flox, Alb-ERT2-Cre) mice exhibited a markedly lower incidence of tumour formation compared with control mice. The underlying mechanism may be that STK33 binds directly to c-Myc and increases its transcriptional activity. In particular, the C-terminus of STK33 blocks STK33/c-Myc association, downregulates HCC cell proliferation, and reduces DEN-induced liver tumour cell number and tumour size.

CONCLUSIONS

STK33 plays an essential role in hepatocellular proliferation and liver tumorigenesis. The C-terminus of STK33 could be a potential therapeutic target in the treatment of patients with STK33-overexpressed HCC.

The serine/threonine kinase 33 is present and expressed in palaeognath birds but has become a unitary pseudogene in neognaths about 100 million years ago

Background

Serine/threonine kinase 33 (STK33) has been shown to be conserved across all major vertebrate classes including reptiles, mammals, amphibians and fish, suggesting its importance within vertebrates. It has been shown to phosphorylate vimentin and might play a role in spermatogenesis and organ ontogenesis. In this study we analyzed the genomic locus and expression of stk33 in the class Aves, using a combination of large scale next generation sequencing data analysis and traditional PCR.

Results

Within the subclass Palaeognathae we analyzed the white-throated tinamou (Tinamus guttatus), the African ostrich (Struthio camelus) and the emu (Dromaius novaehollandiae). For the African ostrich we were able to generate a 62,778 bp long genomic contig and an mRNA sequence that encodes a protein showing highly significant similarity to STK33 proteins from other vertebrates. The emu has been shown to encode and transcribe a functional STK33 as well. For the white-throated tinamou we were able to identify 13 exons by sequence comparison encoding a protein similar to STK33 as well.

In contrast, in all 28 neognath birds analyzed, we could not find evidence for the existence of a functional copy of stk33 or its expression. In the genomes of these 28 bird species, we found only remnants of the stk33 locus carrying several large genomic deletions, leading to the loss of multiple exons. The remaining exons have acquired various indels and premature stop codons.

Conclusions

We were able to elucidate and describe the genomic structure and the transcription of a functional stk33 gene within the subclass Palaeognathae, but we could only find degenerate remnants of stk33 in all neognath birds analyzed. This led us to the conclusion that stk33 became a unitary pseudogene in the evolutionary history of the class Aves at the paleognath-neognath branch point during the late cretaceous period about 100 million years ago. We hypothesize that the pseudogenization of stk33 might have become fixed in neognaths due to either genetic redundancy or a non-orthologous gene displacement and present potential candidate genes for such an incident.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1769-9) contains supplementary material, which is available to authorized users.

Bioregulation

During the 20th century great progress was made in genetics and biochemistry, and these were combined into a molecular biological understanding of functions of macromolecules. Further great discoveries will be made about bioregulations, applicable to scientific problems such as cell development and evolution, and to illnesses including heart disease through defective control of cholesterol production, and to neurological cell-based diseases. The "War Against Cancer" is still far from won. The present generation of scientists can develop clinical applications from recent basic science discoveries.

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.

STK33 overexpression in hypopharyngeal squamous cell carcinoma: possible role in tumorigenesis

BACKGROUND

The role of serine/threonine kinase 33 (STK33) gene in tumorigenesis is still controversial. This study was aimed to investigate whether STK33 had the effect on hypopharyngeal squamous cell carcinoma (HSCC) and relevant genes, as well as the potential relation to ERK1/2 pathway.

METHODS

Immunohistochemistry was performed to investigate STK33 expression in human HSCC specimens. MTT, immunofluorescence, clone formation and matrigel invasion assays were employed to detect the effects of STK33 knockdown (STK33-RNAi) and/or PD98059 on major oncogenic properties of a HSCC cell line (Fadu), while, real-time PCR and western blot were used to examine the expressions of relevant genes.

RESULTS

STK33 was over-expressed in HSCC specimens, which was significantly associated with certain clinicopathological parameters. STK33-RNAi in Fadu cells resulted in inhibition of proliferation, induction of apoptosis, reduction of clone formation, and decline in the migration and invasion. These effects were potentiated by administration of PD98059. Mechanistic studies revealed that STK33-RNAi led to an increase in Caspse-3, Nm-23-H1 and E-Cadherin expressions and a reduction in Bcl-2, Ki-67 and Vimentin expressions. Moreover, PD98059 significantly reduced both ERK1/2 and STK33 expressions in Fadu cells.

CONCLUSIONS

STK33 is a potential oncogene and a promising diagnostic marker for HSCC. STK33 may promote tumorigenesis and progression of HSCC, and serve as a valuable molecular target for treatment of HSCC.

PRKD2: A two-pronged kinase crucial for the tumor-supporting activity of HSP90

PRKD2 plays an important role in tumor cell survival, proliferation, migration, and angiogenesis. We recently reported that cell death and impaired blood vessel formation evoked by inhibition of the HSP90 chaperone in human cancer cells of various tissue origins is mediated by destabilization of PRKD2.