CAPC negatively regulates NF-κB activation and suppresses tumor growth and metastasis

Intracellular Delivery of Stabilized Peptide Blocking MTDH-SND1 Interaction for Breast Cancer Suppression

Triple-negative breast cancer is one of the most prevalent malignant cancers worldwide. Disrupting the MTDH-SND1 protein-protein interaction has recently been shown to be a promising strategy for breast cancer therapy. In this work, a novel potent stabilized peptide with a stronger binding affinity was obtained through rational structure-based optimization. Furthermore, a sulfonium-based peptide delivery system was established to improve the cell penetration and antitumor effects of stabilized peptides in metastatic breast cancer. Our study further broadens the in vivo applications of the stabilized peptides for blocking MTDH-SND1 interaction and provides promising opportunities for breast cancer therapy.

Serine protease inhibitors decrease metastasis in prostate, breast, and ovarian cancers

Targeted therapies for prostate, breast, and ovarian cancers are based on their activity against primary tumors rather than their anti-metastatic activity. Consequently, there is an urgent need for new agents targeting the metastatic process. Emerging evidence correlates in vitro and in vivo cancer invasion and metastasis with increased activity of the proteases mesotrypsin (prostate and breast cancer) and kallikrein 6 (KLK6; ovarian cancer). Thus, mesotrypsin and KLK6 are attractive putative targets for therapeutic intervention. As potential therapeutics for advanced metastatic prostate, breast, and ovarian cancers, we report novel mesotrypsin- and KLK6-based therapies, based on our previously developed mutants of the human amyloid β-protein precursor Kunitz protease inhibitor domain (APPI). These mutants, designated APPI-3M (prostate and breast cancer) and APPI-4M (ovarian cancer), demonstrated significant accumulation in tumors and therapeutic efficacy in orthotopic preclinical models, with the advantages of long retention times in vivo, high affinity and favorable pharmacokinetic properties. The applicability of the APPIs, as a novel therapy and for imaging purposes, is supported by their good safety profile and their controlled and scalable manufacturability in bioreactors.

Peptidase inhibitor (PI16) impairs bladder cancer metastasis by inhibiting NF-κB activation via disrupting multiple-site ubiquitination of NEMO

BACKGROUND

Bladder cancer (BLCA) is a malignancy that frequently metastasizes and leads to poor patient prognosis. It is essential to understand the molecular mechanisms underlying the progression and metastasis of BLCA and identify potential biomarkers.

METHODS

The expression of peptidase inhibitor 16 (PI16) was analysed using quantitative PCR, immunoblotting and immunohistochemistry assays. The functional roles of PI16 were evaluated using wound healing, transwell, and human umbilical vein endothelial cell tube formation assays, as well as in vivo tumour models. The effects of PI16 on nuclear factor κB (NF-κB) signalling activation were examined using luciferase reporter gene systems, immunoblotting and immunofluorescence assays. Co-immunoprecipitation was used to investigate the interaction of PI16 with annexin-A1 (ANXA1) and NEMO.

RESULTS

PI16 expression was downregulated in bladder cancer tissues, and lower PI16 levels correlated with disease progression and poor survival in patients with BLCA. Overexpressing PI16 inhibited BLCA cell growth, motility, invasion and angiogenesis in vitro and in vivo, while silencing PI16 had the opposite effects. Mechanistically, PI16 inhibited the activation of the NF-κB pathway by interacting with ANXA1, which inhibited K63 and M1 ubiquitination of NEMO.

CONCLUSIONS

These results indicate that PI16 functions as a tumour suppressor in BLCA by inhibiting tumour growth and metastasis. Additionally, PI16 may serve as a potential biomarker for metastatic BLCA.

The LRRC family of BK channel regulatory subunits: potential roles in health and disease

Large conductance K+ channels, termed BK channels, regulate a variety of cellular and physiological functions. Although universally activated by changes in voltage or [Ca2+ ]i , the threshold for BK channel activation varies among loci of expression, often arising from cell-specific regulatory subunits including a family of leucine rich repeat-containing (LRRC) γ subunits (LRRC26, LRRC52, LRRC55 and LRRC38). The 'founding' member of this family, LRRC26, was originally identified as a tumour suppressor in various cancers. An LRRC26 knockout (KO) mouse model recently revealed that LRRC26 is also highly expressed in secretory epithelial cells and partners with BK channels in the salivary gland and colonic goblet cells to promote sustained K+ fluxes likely essential for normal secretory function. To accomplish this, LRRC26 negatively shifts the range of BK channel activation such that channels contribute to K+ flux near typical epithelial cell resting conditions. In colon, the absence of LRRC26 increases vulnerability to colitis. LRRC26-containing BK channels are also likely important regulators of epithelial function in other loci, including airways, female reproductive tract and mammary gland. Based on an LRRC52 KO mouse model, LRRC52 regulation of large conductance K+ channels plays a role both in sperm function and in cochlear inner hair cells. Although our understanding of LRRC-containing BK channels remains rudimentary, KO mouse models may help define other organs in which LRRC-containing channels support normal function. A key topic for future work concerns identification of endogenous mechanisms, whether post-translational or via gene regulation, that may impact LRRC-dependent pathologies.

Gene Expression Changes and Associated Pathways Involved in the Progression of Prostate Cancer Advanced Stages

Prostate cancer (PC) is one of the most common cancers among men worldwide, and advanced PCs, such as locally advanced PC (LAPC) and castration-resistant PC (CRPC), present the greatest challenges in clinical management. Current indicators have limited capacity to predict the disease course; therefore, better prognostic markers are greatly needed. In this study, we performed a bioinformatic analysis of The Cancer Genome Atlas (TCGA) datasets, including RNA-Seq data from the prostate adenocarcinoma (PRAD; n = 55) and West Coast Dream Team – metastatic CRPC (WCDT-MCRPC; n = 84) projects, to evaluate the transcriptome changes associated with progression-free survival (PFS) for LAPC and CRPC, respectively. We identified the genes whose expression was positively/negatively correlated with PFS. In LAPC, the genes with the most significant negative correlations were ZC2HC1A, SQLE, and KIF11, and the genes with the most significant positive correlations were SOD3, LRRC26, MIR22HG, MEG3, and MIR29B2CHG. In CRPC, the most significant positive correlations were found for BET1, CTAGE5, IFNGR1, and GIMAP6, and the most significant negative correlations were found for CLPB, PRPF19, ZNF610, MPST, and LINC02001. In addition, we performed a gene network interaction analysis using STRINGdb, which revealed a significant relationship between genes predominantly involved in the cell cycle and characterized by upregulated expression in early recurrence. Based on the results, we propose several genes that can be used as potential prognostic markers.

Multi-omics analysis to identify driving factors in colorectal cancer

Aim: We aim to identify driving genes of colorectal cancer (CRC) through multi-omics analysis. Materials & methods: We downloaded multi-omics data of CRC from The Cancer Genome Atlas dataset. Integrative analysis of single-nucleotide variants, copy number variations, DNA methylation and differentially expressed genes identified candidate genes that carry CRC risk. Kernal genes were extracted from the weighted gene co-expression network analysis. A competing endogenous RNA network composed of CRC-related genes was constructed. Biological roles of genes were further investigated in vitro. Results: We identified LRRC26 and REP15 as novel prognosis-related driving genes for CRC. LRRC26 hindered tumorigenesis of CRC in vitro. Conclusion: Our study identified novel driving genes and may provide new insights into the molecular mechanisms of CRC.

Subunits of BK channels promote breast cancer development and modulate responses to endocrine treatment in preclinical models

BACKGROUND AND PURPOSE

Pore-forming α subunits of the voltage- and Ca²⁺ -activated K⁺ channel with large conductance (BKα) promote malignant phenotypes of breast tumour cells. Auxiliary subunits such as the leucine-rich repeat containing 26 (LRRC26) protein, also termed BKγ1, may be required to permit activation of BK currents at a depolarized resting membrane potential that frequently occur in non-excitable tumour cells.

EXPERIMENTAL APPROACH

Anti-tumour effects of BKα loss were investigated in breast tumour-bearing MMTV-PyMT transgenic BKα knockout (KO) mice, primary MMTV-PyMT cell cultures, and in a syngeneic transplantation model of breast cancer derived from these cells. The therapeutic relevance of BK channels in the context of endocrine treatment was assessed in human breast cancer cell lines expressing either low (MCF-7) or high (MDA-MB-453) levels of BKα and BKγ1, as well as in BKα-negative MDA-MB-157.

KEY RESULTS

BKα promoted breast cancer onset and overall survival in preclinical models. Conversely, lack of BKα and/or knockdown of BKγ1 attenuated proliferation of murine and human breast cancer cells in vitro. At low concentrations, tamoxifen and its major active metabolites stimulated proliferation of BKα/γ1-positive breast cancer cells, independent of the genomic signalling controlled by the oestrogen receptor. Finally, tamoxifen increased the relative survival time of BKα KO but not of wild-type tumour cell recipient mice.

CONCLUSION AND IMPLICATIONS

Breast cancer initiation, progression, and tamoxifen sensitivity depend on functional BK channels thereby providing a rationale for the future exploration of the oncogenic actions of BK channels in clinical outcomes with anti-oestrogen therapy.

Involvement of the γ1 subunit of the large-conductance Ca2+-activated K+ channel in the proliferation of human somatostatinoma cells

Pancreatic neuroendocrine tumors (pNETs) occur due to the abnormal growth of pancreatic islet cells and predominantly develop in the duodenal-pancreatic region. Somatostatinoma is one of the pNETs associated with tumors of pancreatic δ cells, which produce and secrete somatostatin. Limited information is currently available on the pathogenic mechanisms of somatostatinoma. The large-conductance Ca²⁺-activated K⁺ (BK_Ca) channel is expressed in several types of cancer cells and regulates cell proliferation, migration, invasion, and metastasis. In the present study, the functional expression of the BK_Ca channel was examined in a human somatostatinoma QGP-1 cell line. In QGP-1 cells, outward currents were elicited by membrane depolarization at pCa 6.5 (300 nM) in the pipette solution and inhibited by the specific BK_Ca channel blocker, paxilline. Paxilline-sensitive currents were detected, even at pCa 8.0 (10 nM) in the pipette solution, in QGP-1 cells. In addition to the α and β2-4 subunits of the BK_Ca channel, the novel regulatory γ1 subunit (BK_Caγ1) was co-localized with the α subunit in QGP-1 cells. Paxilline-sensitive currents at pCa 8.0 in the pipette solution were reduced by the siRNA knockdown of BK_Caγ1. Store-operated Ca²⁺ entry was smaller in BK_Caγ1 siRNA-treated QGP-1 cells. The proliferation of QGP-1 cells was attenuated by paxilline or the siRNA knockdown of BK_Caγ1. These results strongly suggest that BK_Caγ1 facilitates the proliferation of human somatostatinoma cells. Therefore, BK_Caγ1 may be a novel therapeutic target for somatostatinoma.

Roles of LRRC26 as an auxiliary γ1-subunit of large-conductance Ca2+-activated K+ channels in bronchial smooth muscle cells

In visceral smooth muscle cells (SMCs), the large-conductance Ca²⁺-activated K⁺ (BK) channel is one of the key elements underlying a negative feedback mechanism that is essential for the regulation of intracellular Ca²⁺ concentration. Although leucine-rich repeat-containing (LRRC) proteins have been identified as novel auxiliary γ-subunits of the BK channel (BKγ) in several cell types, its physiological roles in SMCs are unclear. The BKγ expression patterns in selected SM tissues were examined using real-time PCR analyses and Western blotting. The functional contribution of BKγ1 to BK channel activity was examined by whole cell patch-clamp in SMCs and heterologous expression systems. BKγ1 expression in mouse bronchial SMCs (mBSMCs) was higher than in other several SMC types. Coimmunoprecipitation and total internal reflection fluorescence imaging analyses revealed molecular interaction between BKα and BKγ1 in mBSMCs. Under voltage-clamp, steady-state activation of BK channel currents at pCa 8.0 in mBSMCs occurred in a voltage range comparable to that of reconstituted BKα/BKγ1 complex. However, this range was much more negative than in mouse aortic SMCs (mASMCs) or in HEK293 cells expressing BKα alone and β-subunit (BKβ1). Mallotoxin, a selective activator of BK channel that lacks BKγ1, dose-dependently activated BK currents in mASMCs but not in mBSMCs. The abundant expression of BKγ1 in mBSMCs extensively facilitates BK channel activity to keep the resting membrane potential at negative values and prevents contraction under physiological conditions.

Emerging roles for multifunctional ion channel auxiliary subunits in cancer

Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.

HOXC10 overexpression promotes cell proliferation and migration in gastric cancer

Homeodomain‑containing gene 10 (HOXC10) is a member of the homeobox transcription factors that plays an important role in the development of multicellular organisms. HOXC10 is overexpressed in a variety of human cancers, and recent studies have revealed that HOXC10 is upregulated in gastric cancer as well. However, its mechanism of action is not fully understood, thus, the role of HOXC10 was investigated in the present study in human gastric cancer. First, HOXC10 expression was revealed to be significantly increased in gastric cancer tissues compared to normal tissues (TCGA dataset), and HOXC10 upregulation was associated with decreased recurrence‑free survival in gastric cancer patients in a public gene expression dataset. HOXC10 promoted cell proliferation and metastasis in two gastric cancer cell lines (AGS and MKN74). Analyzing TCGA 450K DNA methylation dataset, it was revealed that HOXC10 CpG sites were hypomethylated in gastric cancer tissues. Bisulfite sequencing revealed that CpG sites in the HOXC10 first intronic region were hypomethylated in three gastric cancer tissues, and HOXC10 expression was increased in gastric cancer cell lines (AGS and SNU620) in response to 5‑azacytidine treatment. By RNA‑sequencing of AGS cells with ectopic HOXC10 expression, it was revealed that many genes were upregulated by HOXC10 overexpression. Among them, CST1 was predicted to be a HOXC10 direct target gene via prediction of HOXC10 binding sites from the JASPAR database. A chromatin immunoprecipitation assay revealed that HOXC10 directly bound to CST1 promoter regions. The present study proposes HOXC10 is a potential prognostic marker or therapeutic target in human gastric cancer.

Cystatins in cancer progression: More than just cathepsin inhibitors

Cystatins are endogenous and reversible inhibitors of cysteine peptidases that are important players in cancer progression. Besides their primary role as regulators of cysteine peptidase activity, cystatins are involved in cancer development and progression through proteolysis-independent mechanisms. Mechanistic studies of cystatin function revealed that they affect all stages of cancer progression including tumor growth, apoptosis, invasion, metastasis and angiogenesis. Recently, the involvement of cystatins in the antitumor immune responses was reported. In this review, we discuss molecular mechanisms and clinical aspects of cystatins in cancer. Altered expression of cystatins in cancer resulting in harmful excessive cysteine peptidase activity has been a subject of several studies in order to find correlations with clinical outcome and therapy response. However, involvement in anti-tumor immune response and signaling cascades leading to cancer progression designates cystatins as possible targets for development of new anti-tumor drugs.

Research progress of cystatin SN in cancer

Cystatin SN, belonging to the type 2 cystatin superfamily, is widely expressed and distributed in mammals. Cystatin SN is involved in inflammation, cell cycle, cellular senescence, tumorigenesis, and metastasis. Cystatin SN is also known to participate in signaling pathways like Wnt signaling pathway, GSK3 signaling pathway, AKT signaling pathway, and IL-6 signaling pathway. Cystatin SN was found to be highly expressed in peritumoral normal tissues in esophageal squamous cell carcinoma (ESCC); however, low cystatin SN expression was found in ESCC cancer tissues. Conversely, in other cancer types such as lung cancer, breast cancer, gastric cancer, pancreatic cancer, and colorectal cancer, high cystatin SN expression in cancer tissues but low cystatin SN expression in peritumoral normal tissues was found. Survival analyses showed that high cystatin SN expression benefited ESCC patients but did harm to other types of cancer patients. Univariate and multivariate analyses indicated that cystatin SN possibly acts as a marker for cancer prognosis. Here, we provide a brief introduction about the role of cystatin SN in cancer and discuss the different prognostic effects of cystatin SN on different tumors. Cystatin SN might be a potential marker for cancer prognosis and a target for cancer therapy.

Frequent downregulation of LRRC26 by epigenetic alterations is involved in the malignant progression of triple-negative breast cancer

Triple-negative breast cancer (TNBC), defined as breast cancer lacking estrogen- and progesterone‑receptor expression and human epidermal growth factor receptor 2 (HER2) amplification, is a heterogeneous disease. RNA-sequencing analysis of 15 TNBC specimens and The Cancer Genome Atlas-TNBC dataset analysis identified the frequent downregulation of leucine-rich repeat-containing 26 (LRRC26), which negatively regulates nuclear factor-κB (NF-κB) signaling, in TNBC tissues. Quantitative polymerase chain reaction and bisulfite pyrosequencing analyses revealed that LRRC26 was frequently silenced in TNBC tissues and cell lines as a result of promoter methylation. LRRC26 expression was restored by 5-aza-2'-deoxycytidine (5'-aza-dC) treatment in HCC1937 TNBC cells, which lack LRRC26 expression. Notably, small interfering RNA-mediated knockdown of LRRC26 expression significantly enhanced the anchorage-independent growth, invasion and migration of HCC70 cells, whereas ectopic overexpression of LRRC26 in BT20 cells suppressed their invasion and migration. Conversely, neither knockdown nor overexpression of LRRC26 had an effect on cell viability in the absence of tumor necrosis factor-α (TNF-α) stimulation. Meanwhile, overexpression of LRRC26 caused the reduction of TNF-α-mediated NF-κB luciferase reporter activity, whereas depleting LRRC26 expression resulted in the upregulation of TNF-α-mediated NF-κB downstream genes [interleukin-6 (IL-6), IL-8 and C-X-C motif chemokine ligand-1]. Taken together, these findings demonstrate that LRRC26 is frequently downregulated in TNBC due to DNA methylation and that it suppresses the TNF-α-independent anchorage-independent growth, invasion and migration of TNBC cells. Loss of LRRC26 function may be a critical event in the aggressiveness of TNBC cells through a TNF-α/NF-κB-independent mechanism.

Knockout of the LRRC26 subunit reveals a primary role of LRRC26-containing BK channels in secretory epithelial cells

Leucine-rich-repeat-containing protein 26 (LRRC26) is the regulatory γ1 subunit of Ca²⁺- and voltage-dependent BK-type K⁺ channels. BK channels that contain LRRC26 subunits are active near normal resting potentials even without Ca²⁺, suggesting they play unique physiological roles, likely limited to very specific cell types and cellular functions. By using Lrrc26 KO mice with a β-gal reporter, Lrrc26 promoter activity is found in secretory epithelial cells, especially acinar epithelial cells in lacrimal and salivary glands, and also goblet and Paneth cells in intestine and colon, although absent from neurons. We establish the presence of LRRC26 protein in eight secretory tissues or tissues with significant secretory epithelium and show that LRRC26 protein coassembles with the pore-forming BK α-subunit in at least three tissues: lacrimal gland, parotid gland, and colon. In lacrimal, parotid, and submandibular gland acinar cells, LRRC26 KO shifts BK gating to be like α-subunit-only BK channels. Finally, LRRC26 KO mimics the effect of SLO1/BK KO in reducing [K⁺] in saliva. LRRC26-containing BK channels are competent to contribute to resting K⁺ efflux at normal cell membrane potentials with resting cytosolic Ca²⁺ concentrations and likely play a critical physiological role in supporting normal secretory function in all secretory epithelial cells.

Reduced Shedding of Surface Mesothelin Improves Efficacy of Mesothelin-Targeting Recombinant Immunotoxins

Mesothelin (MSLN) is a differentiation antigen that is highly expressed in many epithelial cancers. MSLN is an important therapeutic target due to its high expression in cancers and limited expression in normal human tissues. Although it has been assumed that shed antigen is a barrier to immunotoxin action, a modeling study predicted that shed MSLN may enhance the action of MSLN-targeting recombinant immunotoxins such as SS1P and similar therapeutics by facilitating their redistribution within tumors. We aimed to determine whether shed MSLN enhances or reduces the antitumor effect of MSLN-targeting immunotoxins SS1P and RG7787. We engineered a cell line, A431/G9 (TACE mutant) that expresses a mutant form of MSLN in which the TNF-converting enzyme protease site is replaced with GGGS. We compared the response of the TACE-mutant cells with immunotoxins SS1P and RG7787 with that of the parental A431/H9 cell line. We show that TACE-mutant cells shed 80% less MSLN than A431/H9 cells, that TACE-mutant cells show a 2- to 3-fold increase in MSLN-targeted immunotoxin uptake, and that they are about 5-fold more sensitive to SS1P killing in cell culture. Tumors with reduced shedding respond significantly better to treatment with SS1P and RG7787. Our data show that MSLN shedding is an impediment to the antitumor activity of SS1P and RG7787. Approaches that decrease MSLN shedding could enhance the efficacy of immunotoxins and immunoconjugates targeting MSLN-expressing tumors. Mol Cancer Ther; 15(7); 1648-55. ©2016 AACR.

Modulation of BK Channel Function by Auxiliary Beta and Gamma Subunits

The large-conductance, Ca(2+)- and voltage-activated K(+) (BK) channel is ubiquitously expressed in mammalian tissues and displays diverse biophysical or pharmacological characteristics. This diversity is in part conferred by channel modulation with different regulatory auxiliary subunits. To date, two distinct classes of BK channel auxiliary subunits have been identified: β subunits and γ subunits. Modulation of BK channels by the four auxiliary β (β1-β4) subunits has been well established and intensively investigated over the past two decades. The auxiliary γ subunits, however, were identified only very recently, which adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. This chapter will review the current understanding of BK channel modulation by auxiliary β and γ subunits, especially the latest findings.

Nuclear Receptor Corepressor 1 Expression and Output Declines with Prostate Cancer Progression

PURPOSE

Castration therapy in advanced prostate cancer eventually fails and leads to the development of castration-resistant prostate cancer (CRPC), which has no cure. Characteristic features of CRPC can be increased androgen receptor (AR) expression and altered transcriptional output. We investigated the expression of nuclear receptor corepressor 1 (NCOR1) in human prostate and prostate cancer and the role of NCOR1 in response to antiandrogens.

EXPERIMENTAL DESIGN

NCOR1 protein levels were compared between matched normal prostate and prostate cancer in 409 patient samples. NCOR1 knockdown was used to investigate its effect on bicalutamide response in androgen-dependent prostate cancer cell lines and transcriptional changes associated with the loss of NCOR1. NCOR1 transcriptional signature was also examined in prostate cancer gene expression datasets.

RESULTS

NCOR1 protein was detected in cytoplasm and nuclei of secretory epithelial cells in normal prostate. Both cytoplasmic and nuclear NCOR1 protein levels were lower in prostate cancer than in normal prostate. Prostate cancer metastases show significant decrease in NCOR1 transcriptional output. Inhibition of LNCaP cellular proliferation by bicalutamide requires NCOR1. NCOR1-regulated genes suppress cellular proliferation and mediate bicalutamide resistance. In the mouse, NCOR1 is required for bicalutamide-dependent regulation of a subset of the AR target genes.

CONCLUSIONS

In summary, we demonstrated that NCOR1 function declines with prostate cancer progression. Reduction in NCOR1 levels causes bicalutamide resistance in LNCaP cells and compromises response to bicalutamide in mouse prostate in vivo Clin Cancer Res; 22(15); 3937-49. ©2016 AACR.

Identification of Differentially Expressed IGFBP5-Related Genes in Breast Cancer Tumor Tissues Using cDNA Microarray Experiments

IGFBP5 is an important regulatory protein in breast cancer progression. We tried to identify differentially expressed genes (DEGs) between breast tumor tissues with IGFBP5 overexpression and their adjacent normal tissues. In this study, thirty-eight breast cancer and adjacent normal breast tissue samples were used to determine IGFBP5 expression by qPCR. cDNA microarrays were applied to the highest IGFBP5 overexpressed tumor samples compared to their adjacent normal breast tissue. Microarray analysis revealed that a total of 186 genes were differentially expressed in breast cancer compared with normal breast tissues. Of the 186 genes, 169 genes were downregulated and 17 genes were upregulated in the tumor samples. KEGG pathway analyses showed that protein digestion and absorption, focal adhesion, salivary secretion, drug metabolism-cytochrome P450, and phenylalanine metabolism pathways are involved. Among these DEGs, the prominent top two genes (MMP11 and COL1A1) which potentially correlated with IGFBP5 were selected for validation using real time RT-qPCR. Only COL1A1 expression showed a consistent upregulation with IGFBP5 expression and COL1A1 and MMP11 were significantly positively correlated. We concluded that the discovery of coordinately expressed genes related with IGFBP5 might contribute to understanding of the molecular mechanism of the function of IGFBP5 in breast cancer. Further functional studies on DEGs and association with IGFBP5 may identify novel biomarkers for clinical applications in breast cancer.

Apoptosis, autophagy, necroptosis, and cancer metastasis

Metastasis is a crucial hallmark of cancer progression, which involves numerous factors including the degradation of the extracellular matrix (ECM), the epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, the development of an inflammatory tumor microenvironment, and defects in programmed cell death. Programmed cell death, such as apoptosis, autophagy, and necroptosis, plays crucial roles in metastatic processes. Malignant tumor cells must overcome these various forms of cell death to metastasize. This review summarizes the recent advances in the understanding of the mechanisms by which key regulators of apoptosis, autophagy, and necroptosis participate in cancer metastasis and discusses the crosstalk between apoptosis, autophagy, and necroptosis involved in the regulation of cancer metastasis.

Systems toxicology approaches enable mechanistic comparison of spontaneous and cigarette smoke-related lung tumor development in the A/J mouse model

The A/J mouse is highly susceptible to lung tumor induction and has been widely used as a screening model in carcinogenicity testing and chemoprevention studies. However, the A/J mouse model has several disadvantages. Most notably, it develops lung tumors spontaneously. Moreover, there is a considerable gap in our understanding of the underlying mechanisms of pulmonary chemical carcinogenesis in the A/J mouse. Therefore, we examined the differences between spontaneous and cigarette smoke-related lung tumors in the A/J mouse model using mRNA and microRNA (miRNA) profiling. Male A/J mice were exposed whole-body to mainstream cigarette smoke (MS) for 18 months. Gene expression interaction term analysis of lung tumors and surrounding non-tumorous parenchyma samples from animals that were exposed to either 300 mg/m³ MS or sham-exposed to fresh air indicated significant differential expression of 296 genes. Ingenuity Pathway Analysis^® (IPA^®) indicated an overall suppression of the humoral immune response, which was accompanied by a disruption of sphingolipid and glycosaminoglycan metabolism and a deregulation of potentially oncogenic miRNA in tumors of MS-exposed A/J mice. Thus, we propose that MS exposure leads to severe perturbations in pathways essential for tumor recognition by the immune system, thereby potentiating the ability of tumor cells to escape from immune surveillance. Further, exposure to MS appeared to affect expression of miRNA, which have previously been implicated in carcinogenesis and are thought to contribute to tumor progression. Finally, we identified a 50-gene expression signature and show its utility in distinguishing between cigarette smoke-related and spontaneous lung tumors.

Regulation of BK channels by auxiliary γ subunits

The large-conductance, calcium- and voltage-activated potassium (BK) channel has the largest single-channel conductance among potassium channels and can be activated by both membrane depolarization and increases in intracellular calcium concentration. BK channels consist of pore-forming, voltage- and calcium-sensing α subunits, either alone or in association with regulatory subunits. BK channels are widely expressed in various tissues and cells including both excitable and non-excitable cells and display diverse biophysical and pharmacological characteristics. This diversity can be explained in part by posttranslational modifications and alternative splicing of the α subunit, which is encoded by a single gene, KCNMA1, as well as by tissue-specific β subunit modulation. Recently, a leucine-rich repeat-containing membrane protein, LRRC26, was found to interact with BK channels and cause an unprecedented large negative shift (~-140 mV) in the voltage dependence of the BK channel activation. LRRC26 allows BK channels to open even at near-physiological calcium concentration and membrane voltage in non-excitable cells. Three LRRC26-related proteins, LRRC52, LRRC55, and LRRC38, were subsequently identified as BK channel modulators. These LRRC proteins are structurally and functionally distinct from the BK channel β subunits and were designated as γ subunits. The discovery of the γ subunits adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. Unlike BK channel β subunits, which have been intensively investigated both mechanistically and physiologically, our understanding of the γ subunits is very limited at this stage. This article reviews the structure, modulatory mechanisms, physiological relevance, and potential therapeutic implications of γ subunits as they are currently understood.

Autoimmune pulmonary alveolar proteinosis co-existing with breast cancer: a case report

Introduction

Pulmonary alveolar proteinosis is a rare pulmonary disease characterized by excessive alveolar accumulation of surfactant due to defective alveolar clearance by macrophages. There are only a few published case reports of pulmonary alveolar proteinosis occurring in association with solid cancers. To the best of our knowledge, there are no previously reported cases of pulmonary alveolar proteinosis associated with breast cancer.

Case presentation

A 48-year-old Asian woman, a nonsmoker, presented to our institution with a right breast mass. Biopsy examination of the lesion revealed scirrhous carcinoma. A chest computed tomography scan for metastases showed abnormal shadows in both upper lung fields. As a result of flexible fiberscopic bronchoscopy, this patient was diagnosed as having pulmonary alveolar proteinosis. This case was categorized as autoimmune pulmonary alveolar proteinosis due to the positive anti-granulocyte-macrophage colony-stimulating factor antibody. Pulmonary alveolar proteinosis decreased gradually after mastectomy.

Conclusions

The present case involved the coincident occurrence of autoimmune pulmonary alveolar proteinosis with breast cancer; breast cancer may be a factor during pulmonary alveolar proteinosis development.

Arsenic exposure in early pregnancy alters genome-wide DNA methylation in cord blood, particularly in boys

Early-life inorganic arsenic exposure influences not only child health and development but also health in later life. The adverse effects of arsenic may be mediated by epigenetic mechanisms, as there are indications that arsenic causes altered DNA methylation of cancer-related genes. The objective was to assess effects of arsenic on genome-wide DNA methylation in newborns. We studied 127 mothers and cord blood of their infants. Arsenic exposure in early and late pregnancy was assessed by concentrations of arsenic metabolites in maternal urine, measured by high performance liquid chromatography-inductively coupled plasma mass spectrometry. Genome-wide 5-methylcytosine methylation in mononuclear cells from cord blood was analyzed by Infinium HumanMethylation450K BeadChip. Urinary arsenic in early gestation was associated with cord blood DNA methylation (Kolmogorov-Smirnov test, P-value<10-15), with more pronounced effects in boys than in girls. In boys, 372 (74%) of the 500 top CpG sites showed lower methylation with increasing arsenic exposure (r S -values>-0.62), but in girls only 207 (41%) showed inverse correlation (r S -values>-0.54). Three CpG sites in boys (cg15255455, cg13659051 and cg17646418), but none in girls, were significantly correlated with arsenic after adjustment for multiple comparisons. The associations between arsenic and DNA methylation were robust in multivariable-adjusted linear regression models. Much weaker associations were observed with arsenic exposure in late compared with early gestation. Pathway analysis showed overrepresentation of affected cancer-related genes in boys, but not in girls. In conclusion, early prenatal arsenic exposure appears to decrease DNA methylation in boys. Associations between early exposure and DNA methylation might reflect interference with de novo DNA methylation.

Antitumor effects of immunotoxins are enhanced by lowering HCK or treatment with SRC kinase inhibitors

Recombinant immunotoxins (RIT) are agents being developed for cancer treatment. They are composed of an Fv that binds to a cancer cell, fused to a 38-kDa fragment of Pseudomonas exotoxin A. SS1P is a RIT that targets mesothelin, a protein expressed on mesothelioma as well as pancreatic, ovarian, lung, and other cancers. Because the protein tyrosine kinase family regulates a variety of cellular processes and pathways, we hypothesized that tyrosine kinases might regulate susceptibility to immunotoxin killing. To investigate their role, we used siRNAs to lower the level of expression of the 88 known tyrosine kinases. We identified five tyrosine kinases, INSR, HCK, SRC, PDGFRβ, and BMX that enhance the activity of SS1P when their level of expression is lowered by siRNAs. We further investigated the Src family member HCK in this study. Knocking down of SRC slightly increased SS1P killing in A431/H9 cells, but knocking down HCK substantially enhanced killing by SS1P. We investigated the mechanism of enhancement and found that HCK knockdown enhanced SS1P cleavage by furin and lowered levels of Mcl-1 and raised Bax. We then found that Src inhibitors mimic the stimulatory effect of HCK knockdown; both SU6656 and SKI-606 (bosutinib) enhanced immunotoxin killing of mesothelin-expressing cells by SS1P and CD22-expressing cells by HA22 (moxetumomab pasudotox). SU6656 also enhanced the antitumor effects of SS1P and HA22 in mouse xenograft tumor models. Our data suggest that the combination of immunotoxin with tyrosine kinase inhibitors may be an effective way to treat some cancers.

PRSS3/mesotrypsin is a therapeutic target for metastatic prostate cancer

PRSS3/mesotrypsin is an atypical isoform of trypsin that has been associated with breast, lung, and pancreatic cancer cell malignancy. In analyses of open source transcriptional microarray data, we find that PRSS3 expression is upregulated in metastatic prostate cancer tissue, and that expression of PRSS3 in primary prostate tumors is prognostic of systemic progression following prostatectomy. Using a mouse orthotopic model with bioluminescent imaging, we show that PRSS3/mesotrypsin is critical for prostate cancer metastasis. Silencing of PRSS3 inhibits anchorage-independent growth of prostate cancer cells in soft agar assays, and suppresses invasiveness in Matrigel transwell assays and three-dimensional (3D) cell culture models. We further show that treatment with recombinant mesotrypsin directly promotes an invasive cellular phenotype in prostate cancer cells and find that these effects are specific and require the proteolytic activity of mesotrypsin, because neither cationic trypsin nor a mesotrypsin mutant lacking activity can drive the invasive phenotype. Finally, we show that a newly developed, potent inhibitor of mesotrypsin activity can suppress prostate cancer cell invasion to a similar extent as PRSS3 gene silencing. This study defines mesotrypsin as an important mediator of prostate cancer progression and metastasis, and suggests that inhibition of mesotrypsin activity may provide a novel modality for prostate cancer treatment.

BK potassium channel modulation by leucine-rich repeat-containing proteins

Molecular diversity of ion channel structure and function underlies variability in electrical signaling in nerve, muscle, and nonexcitable cells. Regulation by variable auxiliary subunits is a major mechanism to generate tissue- or cell-specific diversity of ion channel function. Mammalian large-conductance, voltage- and calcium-activated potassium channels (BK, K(Ca)1.1) are ubiquitously expressed with diverse functions in different tissues or cell types, consisting of the pore-forming, voltage- and Ca(2+)-sensing α-subunits (BKα), either alone or together with the tissue-specific auxiliary β-subunits (β1-β4). We recently identified a leucine-rich repeat (LRR)-containing membrane protein, LRRC26, as a BK channel auxiliary subunit, which causes an unprecedented large negative shift (∼140 mV) in voltage dependence of channel activation. Here we report a group of LRRC26 paralogous proteins, LRRC52, LRRC55, and LRRC38 that potentially function as LRRC26-type auxiliary subunits of BK channels. LRRC52, LRRC55, and LRRC38 produce a marked shift in the BK channel's voltage dependence of activation in the hyperpolarizing direction by ∼100 mV, 50 mV, and 20 mV, respectively, in the absence of calcium. They along with LRRC26 show distinct expression in different human tissues: LRRC26 and LRRC38 mainly in secretory glands, LRRC52 in testis, and LRRC55 in brain. LRRC26 and its paralogs are structurally and functionally distinct from the β-subunits and we designate them as a γ family of the BK channel auxiliary proteins, which potentially regulate the channel's gating properties over a spectrum of different tissues or cell types.