Cyclosporine A inhibits colorectal cancer proliferation probably by regulating expression levels of c-Myc, p21WAF1/CIP1 and proliferating cell nuclear antigen

Dephosphorylation of NFAT by Calcineurin inhibits Skp2-mediated degradation

The transcription factor NFAT plays key roles in multiple biological activities, such as immune responses, tissue development and malignant transformation. NFAT is dephosphorylated by calcineurin, which is activated by intracellular calcium levels, and translocated into the nucleus, resulting in transcriptional activation. Calcineurin dephosphorylates various target proteins and regulates their functions. However, the regulation of NFAT degradation is largely unknown, and it is unclear whether calcineurin contributes to the stability of NFAT. We investigated the effect of calcineurin inhibition on NFAT protein stability and found that the dephosphorylation of NFAT by calcineurin promotes the NFAT stabilization, whereas calcineurin mutant that is defective in phosphatase activity was unable to stabilize NFAT. Increased intracellular calcium ion concentration, which is essential for calcineurin activation, also induced NFAT stability. In addition, we identified S-phase kinase associated protein 2 (Skp2), an F-box protein of the SCF ubiquitin ligase complex, as a factor mediating degradation of NFAT when calcineurin was depleted. In summary, these findings revealed that the dephosphorylation of NFAT by calcineurin protects NFAT from degradation by Skp2 and promotes its protein stability.

WNT16b promotes the proliferation and self-renewal of human limbal epithelial stem/progenitor cells via activating the calcium/calcineurin A/NFATC2 pathway

Our previous finding revealed that WNT16b promoted the proliferation of human limbal epithelial stem cells (hLESCs) through a β-catenin independent pathway. Here, we aimed to explore its underlying molecular mechanism and evaluate its potential in the treatment of limbal stem cell deficiency (LSCD). Based on the findings of mRNA-sequencing, the expression of key molecules in WNT/calcineurin A/NFATC2 signalling pathway was investigated in WNT16b-co-incubated hLESCs and control hLESCs. An epithelial wound healing model was established on Wnt16b-KO mice to confirm the regulatory effect of WNT16b in vivo. The therapeutic potential of WNT16b-co-incubated hLESCs was also evaluated in mice with LSCD. Our findings showed that WNT16b bound with Frizzled7, promoted the release of Ca2+ and activated calcineurin A and NFATC2. With the translocation of NFATC2 into cell nucleus and the activation of HDAC3, WDR5 and GCN5L2, the expression of H3K4me3, H3K14ac and H3K27ac in the promoter regions of FoxM1 and c-MYC increased, which led to hLESC proliferation. The effect of the WNT16b/calcium/calcineurin A/NFATC2 pathway on LESC homeostasis maintenance and corneal epithelial repair was confirmed in Wnt16b-KO mice. Moreover, WNT16b-coincubated hLESCs could reconstruct a stable ocular surface and inhibit corneal neovascularization in mice with LSCD. In conclusion, WNT16b enhances the proliferation and maintains the stemness of hLESCs by activating the non-canonical calcium/calcineurin A/NFATC2 pathway in vitro and in vivo, and accelerates corneal epithelial wound healing.

Differential dose-response effect of cyclosporine A in regulating apoptosis and autophagy markers in MCF-7 cells

Cyclosporine A (CsA) is an immunosuppressant primarily used at a higher dosage in transplant medicine and autoimmune diseases with a higher success rate. At lower doses, CsA exhibits immunomodulatory properties. CsA has also been reported to inhibit breast cancer cell growth by downregulating the expression of pyruvate kinase. However, differential dose-response effects of CsA in cell growth, colonization, apoptosis, and autophagy remain largely unidentified in breast cancer cells. Herein, we showed the cell growth-inhibiting effects of CsA by preventing cell colonization and enhancing DNA damage and apoptotic index at a relatively lower concentration of 2 µM in MCF-7 breast cancer cells. However, at a higher concentration of 20 µM, CsA leads to differential expression of autophagy-related genes ATG1, ATG8, and ATG9 and apoptosis-associated markers, such as Bcl-2, Bcl-XL, Bad, and Bax, indicating a dose-response effect on differential cell death mechanisms in MCF-7 cells. This was confirmed in the protein-protein interaction network of COX-2 (PTGS2), a prime target of CsA, which had close interactions with Bcl-2, p53, EGFR, and STAT3. Furthermore, we investigated the combined effect of CsA with SHP2/PI3K-AKT inhibitors showing significant MCF-7 cell growth reduction, suggesting its potential to use as an adjuvant during breast cancer therapy.

Dephosphorylation of the EGFR protein by calcineurin at serine 1046/1047 enhances its stability

The epidermal growth factor receptor (EGFR) is highly expressed or abnormally activated in several types of cancers, such as lung and colorectal cancers. Inhibitors that suppress the tyrosine kinase activity of EGFR have been used in the treatment of lung cancer. However, resistance to these inhibitors has become an issue in cancer treatment, and the development of new therapies that inhibit EGFR is desired. We found that calcineurin, a Ca²⁺/calmodulin-activated serine/threonine phosphatase, is a novel regulator of EGFR. Inhibition of calcineurin by FK506 treatment or calcineurin depletion promoted EGFR degradation in cancer cells. In addition, we found that calcineurin dephosphorylates EGFR at serine (S)1046/1047, which in turn stabilizes EGFR. Furthermore, in human colon cancer cells transplanted into mice, the inhibition of calcineurin by FK506 decreased EGFR expression. These results indicate that calcineurin stabilizes EGFR by dephosphorylating S1046/1047 and promotes tumor growth. These findings suggest that calcineurin may be a new therapeutic target for cancers with high EGFR expression or activation.

Significant position of C-myc in colorectal cancer: a promising therapeutic target

Colorectal cancer (CRC) is a malignant tumor initiating from the mucosa of the colorectum. According to the 2020 statistics from the World Health Organization, there are 10.0% CRC cases among all 19.3 million new cancers, followed by lung and breast cancer, and 9.4% CRC cases among all 9.9 million cancer deaths, ranking second. The population of CRC patients in China is large, and its incidence and mortality continue to increase each year. Despite the continuous development of surgical methods, chemotherapy, radiotherapy, targeted therapy and immunotherapy, the overall survival of CRC patients remains low. Past research has suggested that c-myc plays a pivotal role in the development of CRC. A higher expression level of c-Myc is a negative prognostic marker in CRC. However, there are few drugs targeting c-myc directly. Therefore, we focused on discovering the mechanism of c-myc in CRC to provide a reference for a better therapy choice for patients.

RCAN1-mediated calcineurin inhibition as a target for cancer therapy

Cancer is the leading cause of mortality worldwide. Regulator of calcineurin 1 (RCAN1), as a patent endogenous inhibitor of calcineurin, plays crucial roles in the pathogenesis of cancers. Except for hypopharyngeal and laryngopharynx cancer, high expression of RCAN1 inhibits tumor progression. Molecular antitumor functions of RCAN1 are largely dependent on calcineurin. In this review, we highlight current research on RCAN1 characteristics, and the interaction between RCAN1 and calcineurin. Moreover, the dysregulation of RCAN1 in various cancers is reviewed, and the potential of targeting RCAN1 as a new therapeutic approach is discussed.

C-MYC induces idiopathic pulmonary fibrosis via modulation of miR-9-5p-mediated TBPL1

We sought to pinpoint the potential role of C-MYC in pulmonary fibroblast proliferation in idiopathic pulmonary fibrosis (IPF) and its mechanism. A mouse model of IPF was established by injection of bleomycin. C-MYC and miR-9-5p expression was determined by RT-qPCR and Western blot analysis. The interaction among C-MYC, miR-9-5p, and TBPL1 was detected by ChIP assay and dual luciferase reporter gene assay. After alteration of C-MYC, miR-9-5p, and TBPL1, their roles in pulmonary fibrosis and collagen fiber deposition in mice as well as proliferation and differentiation of pulmonary fibroblasts were assessed. Upregulated C-MYC expression was seen in the lung tissues of IPF mice and its silencing retarded IPF in mice. C-MYC could activate miR-9-5p that negatively regulated TBPL1 expression. Up-regulated C-MYC promoted proliferation and differentiation of pulmonary fibroblasts by inhibiting TBPL1 via activation of miR-9-5p, thus triggering IPF. Moreover, in the lung tissues-derived cells of IPF mice, C-MYC inhibitor, 10,058-F4, was observed to inhibit miR-9-5p expression, thereby repressing pulmonary fibrosis by up-regulating TBPL1. Our data provided evidence pinpointed the aggravative role of C-MYC in IPF by activating miR-9-5p to regulate TBPL1 expression.

Decoding the Phosphatase Code: Regulation of Cell Proliferation by Calcineurin

Calcineurin, a calcium-dependent serine/threonine phosphatase, integrates the alterations in intracellular calcium levels into downstream signaling pathways by regulating the phosphorylation states of several targets. Intracellular Ca²⁺ is essential for normal cellular physiology and cell cycle progression at certain critical stages of the cell cycle. Recently, it was reported that calcineurin is activated in a variety of cancers. Given that abnormalities in calcineurin signaling can lead to malignant growth and cancer, the calcineurin signaling pathway could be a potential target for cancer treatment. For example, NFAT, a typical substrate of calcineurin, activates the genes that promote cell proliferation. Furthermore, cyclin D1 and estrogen receptors are dephosphorylated and stabilized by calcineurin, leading to cell proliferation. In this review, we focus on the cell proliferative functions and regulatory mechanisms of calcineurin and summarize the various substrates of calcineurin. We also describe recent advances regarding dysregulation of the calcineurin activity in cancer cells. We hope that this review will provide new insights into the potential role of calcineurin in cancer development.

Discovery and development of tumor glycolysis rate-limiting enzyme inhibitors

Tumor cells mainly provide necessary energy and substances for rapid cell growth through aerobic perglycolysis rather than oxidative phosphorylation. This phenomenon is called the "Warburg effect". The mechanism of glycolysis in tumor cells is more complicated, which is caused by the comprehensive regulation of multiple factors. Abnormal enzyme metabolism is one of the main influencing factors and inhibiting the three main rate-limiting enzymes in glycolysis is thought to be important strategy for cancer treatment. Therefore, numerous inhibitors of glycolysis rate-limiting enzyme have been developed in recent years, such as the latest HKII inhibitor and PKM2 inhibitor Pachymic acid (PA) and N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide. The review focuses on source, structure-activity relationship, bioecological activity and mechanism of the three main rate-limiting enzymes inhibitors, and hopes to guide the future research on the design and synthesis of rate-limiting enzyme inhibitors.

Strategies for Targeting Serine/Threonine Protein Phosphatases with Small Molecules in Cancer

Among numerous posttranslational regulation patterns, phosphorylation is reversibly controlled by the balance of kinases and phosphatases. The major form of cellular signaling involves the reversible phosphorylation of proteins on tyrosine, serine, or threonine residues. However, altered phosphorylation levels are found in diverse diseases, including cancer, making kinases and phosphatases ideal drug targets. In contrast to the success of prosperous kinase inhibitors, design of small molecules targeting phosphatase is struggling due to past bias and difficulty. This is especially true for serine/threonine phosphatases, one of the largest phosphatase families. From this perspective, we aim to provide insights into serine/threonine phosphatases and the small molecules targeting these proteins for drug development, especially in cancer. Through highlighting the modulation strategies, we aim to provide basic principles for the design of small molecules and future perspectives for the application of drugs targeting serine/threonine phosphatases.

Cyclosporin in dermatology: A practical compendium

Cyclosporine A (CYA) belongs to calcineurin inhibitor family, which has the ability to selectively suppress T cells. Owing to its immune-modulatory effects, it had been in use for graft vs host diseases and organ transplant rejection for many years, but in dermatology, it was first approved for use in 1997 in the treatment of psoriasis. Other off-label indications for skin diseases include atopic dermatitis, chronic spontaneous urticaria, lichen planus, pyoderma gangrenosum, alopecia areata, granuloma annulare, and several others. A thorough search of Medline-PubMed database, Google Scholar, and Uptodate was performed for evidence-based and peer-reviewed information. We have summarized the use of cyclosporine in dermatological diseases with respect to its, dosage, safety considerations, and monitoring guidelines. Furthermore, brief overview of its pharmacology, drug interactions, use in pregnancy, and lactation has been discussed. Despite of its common adverse effects like nephrotoxicity and hypertension, cyclosporine offers good safety profile when used in skin diseases. Decision to start cyclosporine therapy is individualized and it should be based on analysis of risk vs benefit. Nevertheless, CYA is preferred over other immunosuppressants in dermatology because of early therapeutic response and less myelosupression. This article offers concise but detailed summary of this beneficial immune-suppressive agent in skin diseases.

The critical role of calcineurin/NFAT (C/N) pathways and effective antitumor prospect for colorectal cancers

Transcription factors (TFs) like a nuclear factor of activated T-cells (NFAT) and its controller calcineurin are highly expressed in primary intestinal epithelial cells (IECs) due to delamination, damage by tumor-associated flora and selective activation in the intestinal tract tumor are crucial in the progression and growth of colorectal cancer (CRC). This study sought to summarize the current findings concerning the dysregulated calcineurin/NFAT (C/N) signaling involved in CRC initiation and progression. These signalings include proliferation, T-cell functions, and glycolysis with high lactate production that remodels the acidosis, which genes in tumor cells provide an evolutionary advantage, or even increased their attack phenotype. Moreover, the relationship between C/N and gut microbiome in CRC, especially role of NFAT and toll-like receptor signaling in regulating intestinal microbiota are also discussed. Furthermore, this review will discuss the proteins and genes relating to C/N induced acidosis in CRC, which includes ASIC2 regulated C/N1 and TFs associated with the glycolytic by-product that affect T-cell functions and CRC cell growth. It is revealed that calcineurin or NFAT targeting to antitumor, selective calcineurin inhibition or targets in NFAT signaling may be useful for clinical treatment of CRC. This can further aid in the identification of specific targets via cancer patient-personalized approach. Future studies should be focused on targeting to C/N or TLR signaling by the combination of therapeutic agents to regulate T-cell functions and gut microbiome for activating potent anticancer property with the prospect of potentiating the antitumor therapy for CRC.

Lessons to Learn From Low-Dose Cyclosporin-A: A New Approach for Unexpected Clinical Applications

Cyclosporin-A has been known and used for a long time, since its "fast track" approval in the early 80's. This molecule has rapidly demonstrated unexpected immunosuppressive properties, transforming the history of organ transplantation. Cyclosporin's key effect relies on modulation on T-lymphocyte activity, which explains its role in the prevention of graft rejection. However, whether cyclosporin-A exerts other effects on immune system remains to be determined. Until recently, cyclosporin-A was mainly used at a high-dose, but given the drug toxicity and despite the fear of losing its immunosuppressive effects, there is nowadays a tendency to decrease its dose. The literature has been reporting data revealing a paradoxical effect of low dosage of cyclosporin-A. These low-doses appear to have immunomodulatory properties, with different effects from high-doses on CD8+ T lymphocyte activation, auto-immune diseases, graft-vs.-host disease and cancer. The aim of this review is to discuss the role of cyclosporin-A, not only as a consecrated immunosuppressive agent, but also as an immunomodulatory drug when administrated at low-dose. The use of low-dose cyclosporin-A may become a new therapeutic strategy, particularly to treat cancer.

Gut Microbiota-Mediated Bile Acid Transformations Alter the Cellular Response to Multidrug Resistant Transporter Substrates in Vitro: Focus on P-glycoprotein

Pharmacokinetic research at the host-microbe interface has been primarily directed toward effects on drug metabolism, with fewer investigations considering the absorption process. We previously demonstrated that the transcriptional expression of genes encoding intestinal transporters involved in lipid translocation are altered in germ-free and conventionalized mice possessing distinct bile acid signatures. It was consequently hypothesized that microbial bile acid metabolism, which is the deconjugation and dehydroxylation of the bile acid steroid nucleus by gut bacteria, may impact upon drug transporter expression and/or activity and potentially alter drug disposition. Using a panel of three human intestinal cell lines (Caco-2, T84, and HT-29) that differ in basal transporter expression level, bile acid conjugation-, and hydroxylation-status was shown to influence the transcription of genes encoding several major influx and efflux transporter proteins. We further investigated if these effects on transporter mRNA would translate to altered drug disposition and activity. The results demonstrated that the conjugation and hydroxylation status of the bile acid steroid nucleus can influence the cellular response to multidrug resistance (MDR) substrates, a finding that did not directly correlate with directionality of gene or protein expression. In particular, we noted that the cytotoxicity of cyclosporine A was significantly augmented in the presence of the unconjugated bile acids deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) in P-gp positive cell lines, as compared to their taurine/glycine-conjugated counterparts, implicating P-gp in the molecular response. Overall this work identifies a novel mechanism by which gut microbial metabolites may influence drug accumulation and suggests a potential role for the microbial bile acid-deconjugating enzyme bile salt hydrolase (BSH) in ameliorating multidrug resistance through the generation of bile acid species with the capacity to access and inhibit P-gp ATPase. The physicochemical property of nonionization is suggested to underpin the preferential ability of unconjugated bile acids to attenuate the efflux of P-gp substrates and to sensitize tumorigenic cells to cytotoxic therapeutics in vitro. This work provides new impetus to investigate whether perturbation of the gut microbiota, and thereby the bile acid component of the intestinal metabolome, could alter drug pharmacokinetics in vivo. These findings may additionally contribute to the development of less toxic P-gp modulators, which could overcome MDR.

Raddeanin A inhibits growth and induces apoptosis in human colorectal cancer through downregulating the Wnt/β-catenin and NF-κB signaling pathway

AIMS

Colorectal cancer (CRC) remains one of the most lethal human malignancies with high incidence and lack of effective therapy. Raddeanin A (RA), an active triterpenoid saponins, has been demonstrated the ability to inhibit the growth of tumor. But the therapeutic effects and mechanisms of RA in CRC remain elusive. Here, we investigated the efficacy and mechanism of RA in CRC both in vitro and in vivo.

MAIN METHODS

Cell viability was investigated to evaluate cytotoxic activity by MTT method. Apoptosis induced by RA was studied using Annexin V-FITC/PI binding and JC-1 staining by flow cytometry analysis. The xenograft mouse model of CRC was used to investigate anti-tumor effects in vivo. The key proteins involved in mitochondrial apoptotic, Wnt/β-catenin and NF-κB pathway were detected by Western blotting, Immunofluorescence, and Immunohistochemistry.

KEY FINDINGS

RA induced apoptosis and inhibited cell proliferation of SW480 and LOVO cells in a concentration-dependent manner. Moreover, RA efficiently inhibited tumor growth in xenograft mouse model. RA could down regulate the Wnt/β-catenin signaling to display anti-tumor effects via suppression of p-LRP6, induction of AKT inactivation, removal of GSK-3β inhibition and attenuation of β-catenin. Meanwhile, RA also suppressed the NF-κB pathway by decreasing the phosphorylation of IKBα to induce subsequently mitochondrial apoptotic pathway.

SIGNIFICANCE

In summary, RA suppressed the growth and triggered the apoptosis of CRC through discontinuing Wnt/β-catenin signaling and inhibiting the NF-κB pathway. These findings suggested that RA may hold a promise as a novel therapeutic agent for CRC therapy.

Cyclophilin D counteracts P53-mediated growth arrest and promotes Ras tumorigenesis

Mitochondrial alterations induced by oncogenes are known to be crucial for tumorigenesis. Ras oncogene leads to proliferative signals through a Raf-1/MEK/ERK kinase cascade, whose components have been found to be also associated with mitochondria. The mitochondrial pepdidyl-prolyl isomerase cyclophilin D (CypD) is an important regulator of the mitochondrial permeability transition and a key player in mitochondria physiology; however, its role in cancer is still unclear. Using cellular and in vivo mouse models, we demonstrated that CypD protein upregulation induced by oncogenic Ras through the Raf-1/MEK/ERK pathway has a deterministic role in tumor progression. In fact, targeting CypD gene expression clearly affected RasV12-induced transformation, as showed by in vitro data on murine NIH3T3 and human MCF10A mammary epithelial cells. In addition, studies in xenograft and K-Ras lung cancer mouse models demonstrated that genetic deletion or pharmacological suppression of CypD efficiently prevented Ras-dependent tumor formation. Furthermore, Erbb2-mediated breast tumorigenesis was similarly prevented by targeting CypD. From a mechanistic point of view, CypD expression was associated with a reduced induction of p21(WAF1/CIP1) and p53 functions, unraveling an antagonistic function of CypD on p21-p53-mediated growth suppression. CypD activity is p53 dependent. Interestingly, a physical association between p53 and CypD was detected in mitochondria of MCF10A cells; furthermore, both in vitro and in vivo studies proved that CypD inhibitor-based treatment was able to efficiently impair this interaction, leading to a tumor formation reduction. All together, these findings indicate that the countering effect of CypD on the p53-p21 pathway participates in oncogene-dependent transformation.

Inhibiting NFAT1 for breast cancer therapy: New insights into the mechanism of action of MDM2 inhibitor JapA

Transcription factor NFAT1 has been recently identified as a new regulator of the MDM2 oncogene. Targeting the NFAT1-MDM2 pathway represents a novel approach to cancer therapy. We have recently identified a natural product MDM2 inhibitor, termed JapA. As a specific and potent MDM2 inhibitor, JapA inhibits MDM2 at transcriptional and post-translational levels. However, the molecular mechanism remains to be fully elucidated for its inhibitory effects on MDM2 transcription. Herein, we reported that JapA inhibited NFAT1 and NFAT1-mediated MDM2 transcription, which contributed to the anticancer activity of JapA. Its effects on the expression and activity of NFAT1 were examined in various breast cancer cell lines in vitro and in MCF-7 and MDA-MB-231 xenograft tumors in vivo. The specificity of JapA in targeting NFAT1 and NFAT1-MDM2 pathway and the importance of NFAT1 inhibition in JapA's anticancer activity were demonstrated using NFAT1 overexpression and knockdown cell lines and the pharmacological activators and inhibitors of NFAT1 signaling. Our results indicated that JapA inhibited NFAT1 signaling in breast cancer cells in vitro and in vivo, which plays a pivotal role in its anticancer activity. JapA inhibited the nuclear localization of NFAT1, disrupted the NFAT1-MDM2 P2 promoter complex, and induced NFAT1 proteasomal degradation, resulting in the repression of MDM2 transcription. In conclusion, JapA is a novel NFAT1 inhibitor and the NFAT1 inhibition is responsible for the JapA-induced repression of MDM2 transcription, contributing to its anticancer activity. The results may pave an avenue for validating the NFAT1-MDM2 pathway as a novel molecular target for cancer therapy.

KRAS mutation leads to decreased expression of regulator of calcineurin 2, resulting in tumor proliferation in colorectal cancer

KRAS mutations occur in 30–40% of all cases of human colorectal cancer (CRC). However, to date, specific therapeutic agents against KRAS-mutated CRC have not been developed. We previously described the generation of mouse models of colon cancer with and without Kras mutations (CDX2P-G22Cre;Apc^flox/flox; LSL-Kras^G12D and CDX2P-G22Cre;Apc^flox/flox mice, respectively). Here, the two mouse models were compared to identify candidate genes, which may represent novel therapeutic targets or predictive biomarkers. Differentially expressed genes in tumors from the two mouse models were identified using microarray analysis, and their expression was compared by quantitative reverse transcription–PCR (qRT–PCR) and immunohistochemical analyses in mouse tumors and surgical specimens of human CRC, with or without KRAS mutations, respectively. Furthermore, the functions of candidate genes were studied using human CRC cell lines. Microarray analysis of 34 000 transcripts resulted in the identification of 19 candidate genes. qRT–PCR analysis data showed that four of these candidate genes (Clps, Irx5, Bex1 and Rcan2) exhibited decreased expression in the Kras-mutated mouse model. The expression of the regulator of calcineurin 2 (RCAN2) was also observed to be lower in KRAS-mutated human CRC. Moreover, inhibitory function for cancer cell proliferation dependent on calcineurin was indicated with overexpression and short hairpin RNA knockdown of RCAN2 in human CRC cell lines. KRAS mutations in CRC lead to a decrease in RCAN2 expression, resulting in tumor proliferation due to derepression of calcineurin–nuclear factor of activated T cells (NFAT) signaling. Our findings suggest that calcineurin–NFAT signal may represent a novel molecular target for the treatment of KRAS-mutated CRC.

Increased Calcineurin A Expression Is Associated with a Lower Relapse-Free Survival Rate after Colorectal Cancer Surgery

OBJECTIVE

Increased expression of calcineurin in colorectal cancer (CRC) has been reported. Although the oncogenic function has been suggested, the clinical relevance is still unclear. We herein studied calcineurin expression as a prognostic biomarker in patients receiving curative surgery for stages I-III CRC.

METHODS

In 121 patients with stages I-III CRC treated at Hiroshima University between 1997 and 2003, calcineurin A expression was examined using immunohistochemistry (IHC) staining of surgical specimens. Specimens were considered positive for calcineurin A if any IHC-stained cells were observed within the carcinomatous area, and clinicopathological characteristics and survival outcomes were compared between IHC-positive and -negative groups.

RESULTS

Calcineurin A was preferentially expressed in the cytoplasm of cancer cells, and a median of 8% of the cells (range: 0-80%; interquartile range: 0-22.5%) were stained within the carcinomatous areas. Of 121 cases, 81 were determined as IHC positive while 40 were determined to be negative. Positive expression of calcineurin A, as well UICC-TNM stage, was associated with low relapse-free survival (RFS) rates in multivariate analyses (hazard ratio = 2.92; 95% CI: 1.27-7.92; p = 0.010).

CONCLUSION

Increased calcineurin A expression is associated with lower RFS rates and may have clinical value in predicting recurrence.

Epithelial calcineurin controls microbiota-dependent intestinal tumor development

Inflammation-associated pathways are active in intestinal epithelial cells (IECs) and contribute to the pathogenesis of colorectal cancer (CRC). Calcineurin, a phosphatase required for the activation of the nuclear factor of activated T cells (NFAT) family of transcription factors, shows increased expression in CRC. We therefore investigated the role of calcineurin in intestinal tumor development. We demonstrate that calcineurin and NFAT factors are constitutively expressed by primary IECs and selectively activated in intestinal tumors as a result of impaired stratification of the tumor-associated microbiota and toll-like receptor signaling. Epithelial calcineurin supports the survival and proliferation of cancer stem cells in an NFAT-dependent manner and promotes the development of intestinal tumors in mice. Moreover, somatic mutations that have been identified in human CRC are associated with constitutive activation of calcineurin, whereas nuclear translocation of NFAT is associated with increased death from CRC. These findings highlight an epithelial cell-intrinsic pathway that integrates signals derived from the commensal microbiota to promote intestinal tumor development.

Selective dysfunction of p53 for mitochondrial biogenesis induces cellular proliferation in bronchial smooth muscle from asthmatic patients

BACKGROUND

Increase of bronchial smooth muscle (BSM) mass is a crucial feature of asthma remodeling. The mechanisms of such an increased BSM mass are complex but involve enhanced mitochondrial biogenesis, leading to increased proliferation of BSM cells in asthmatic patients. The major tumor suppressor protein p53 is a key cell regulator involved in cell proliferation and has also been implicated in mitochondrial biogenesis. However, the role of p53 in BSM cell proliferation and mitochondrial biogenesis has not been investigated thus far.

OBJECTIVE

We sought to evaluate the role of p53 in proliferation of BSM cells in asthmatic patients and mitochondrial biogenesis.

METHODS

The expression of p53 was assessed both in vitro by using flow cytometry and Western blotting and ex vivo by using RT-PCR after laser microdissection. The role of p53 was assessed with small hairpin RNA lentivirus in both asthmatic patients and control subjects with BSM cell proliferation by using 5-bromo-2'-deoxyuridine and cell counting and in the expression of p21, BCL2-associated X protein, mitochondrial transcription factor A (TFAM), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α).

RESULTS

Twenty-nine patients with moderate-to-severe asthma and 26 control subjects were enrolled in the study. p53 expression was increased in BSM from asthmatic patients both ex vivo and in vitro, with a decreased interaction with mouse double minute 2 homolog (Mdm2) and an increased phosphorylation of serine 20. p53 did not inhibit the transcription of both TFAM and PGC-1α in BSM cells from asthmatic patients. As a consequence, p53 is unable to slow the increased mitochondrial biogenesis and hence the subsequent increased proliferation of BSM cells in asthmatic patients.

CONCLUSION

This study suggests that p53 might act as a new potential therapeutic target against BSM remodeling in asthmatic patients.

NFAT as cancer target: mission possible?

The NFAT signaling pathway regulates various aspects of cellular functions; NFAT acts as a calcium sensor, integrating calcium signaling with other pathways involved in development and growth, immune response, and inflammatory response. The NFAT family of transcription factors regulates diverse cellular functions such as cell survival, proliferation, migration, invasion, and angiogenesis. The NFAT isoforms are constitutively activated and overexpressed in several cancer types wherein they transactivate downstream targets that play important roles in cancer development and progression. Though the NFAT family has been conclusively proved to be pivotal in cancer progression, the different isoforms play distinct roles in different cellular contexts. In this review, our discussion is focused on the mechanisms that drive the activation of various NFAT isoforms in cancer. Additionally, we analyze the potential of NFAT as a valid target for cancer prevention and therapy.

Antiproliferative and apoptotic-inducing potential of ellagic acid against 1,2-dimethyl hydrazine-induced colon tumorigenesis in Wistar rats

Colon cancer remains one of the major worldwide causes of cancer-related morbidity and mortality in Western countries and is increasingly common in Asia. Ellagic acid (EA), a major component of polyphenol possesses attractive remedial features. The aim of this study is to divulge the potential effect of EA during 1,2-dimethyl hydrazine (DMH)-induced colon cancer in male Wistar albino rats. The rats were segregated into four groups: group I, control rats; group II, rats received EA (60 mg/kg b.wt./day, orally); rats in group III, induced with DMH (20 mg/kg b.wt.) subcutaneously for 15 weeks; DMH-induced group IV rats were initiated with EA treatment. Colon of the rats treated with DMH exhibited higher glycoconjugates and proliferation index such as elevated expressions of argyrophilic nucleolar organizing regions (AgNORs), proliferating cell nuclear antigen (PCNA), cyclin D1, matrix metalloproteins (MMP-2 and -9), and mast cells. DMH induction also increased phase I-metabolizing enzymes with simultaneous decrease in the phase II detoxifying enzymes. In contrast, dietary administration of EA significantly (p < 0.05) down regulated the proliferation index and restored back the levels of biotransformation enzymes. The carcinogenic insult also altered the expression of pro-apoptotic protein p53, whereas dietary EA administration significantly (p < 0.01) up regulates p53 expression to further induce apoptotic pathway. Ultrastructural changes in colon were also in accord with the above aberrations. Overall findings suggested that the suppression of colon cancer by EA in vivo involves inhibition of cell proliferation, activation of apoptosis, and efficient detoxification.

Cyclosporin A inhibits colon cancer cell growth independently of the calcineurin pathway

Chronic inflammation is a risk factor for the development of colon cancer, providing genotoxic insults, growth and pro-angiogenic factors that can promote tumorigenesis and tumor growth. Immunomodulatory agents can interfere with the inflammation that feeds cancer, but their impact on the transformed cell is poorly understood. The calcium/calcineurin signaling pathway, through activation of NFAT, is essential for effective immune responses, and its inhibitors cyclosporin A (CsA) and FK506 are used in the clinics to suppress immunity. Moreover, the kinases GSK3β and mTOR, modulated by PI-3K/Akt, can inhibit NFAT activity, suggesting a cross-talk between the calcium and growth factor signaling pathways. Both NFAT and mTOR activity have been associated with tumorigenesis. We therefore investigated the impact of calcineurin and PI-3K/mTOR inhibition in growth of human colon carcinoma cells. We show that despite the efficient inhibition of NFAT1 activity, FK506 promotes tumor growth, whereas CsA inhibits it due to a delay in cell cycle progression and induction of necroptosis. We found NFκB activation and mTORC1 activity not to be altered by CsA or FK506. Similarly, changes to mitochondrial homeostasis were equivalent upon treatment with these drugs. We further show that, in our model, NFAT1 activation is not modulated by PI3K/mTOR. We conclude that CsA slows cell cycle progression and induces necroptosis of human carcinoma cell lines in a TGFβ-, NFAT-, NFκB- and PI3K/mTOR-independent fashion. Nevertheless, our data suggest that CsA, in addition to its anti-inflammatory capacity, may target transformed colon and esophagus carcinoma cells without affecting non-transformed cells, promoting beneficial tumoristatic effects.

Examining the relationship between diet-induced acidosis and cancer

Increased cancer risk is associated with select dietary factors. Dietary lifestyles can alter systemic acid-base balance over time. Acidogenic diets, which are typically high in animal protein and salt and low in fruits and vegetables, can lead to a sub-clinical or low-grade state of metabolic acidosis. The relationship between diet and cancer risk prompts questions about the role of acidosis in the initiation and progression of cancer. Cancer is triggered by genetic and epigenetic perturbations in the normal cell, but it has become clear that microenvironmental and systemic factors exert modifying effects on cancer cell development. While there are no studies showing a direct link between diet-induced acidosis and cancer, acid-base disequilibrium has been shown to modulate molecular activity including adrenal glucocorticoid, insulin growth factor (IGF-1), and adipocyte cytokine signaling, dysregulated cellular metabolism, and osteoclast activation, which may serve as intermediary or downstream effectors of carcinogenesis or tumor promotion. In short, diet-induced acidosis may influence molecular activities at the cellular level that promote carcinogenesis or tumor progression. This review defines the relationship between dietary lifestyle and acid-base balance and discusses the potential consequences of diet-induced acidosis and cancer occurrence or progression.

Cyclosporine A inhibits breast cancer cell growth by downregulating the expression of pyruvate kinase subtype M2

The high proliferative rate of tumor cells leads to metabolic needs distinct from those of their normal counterparts. An embryonic- and tumor-specific isoform of the enzyme pyruvate kinase M2 (PKM2) is overexpressed in cancer cells to increase the use of glycolytic intermediates for macromolecular biosynthesis and tumor growth. We report that Cyclosporin A (CsA) can regulate the expression and activity of PKM2 in breast cancer cell lines MCF-7, MDA-MB-435 and MDA-MB-231. PKM2 was found to be highly expressed in the three breast cancer cell lines compared to normal primary breast cells. Treatment with CsA inhibited the viability of breast cancer cells in a time- and dose-dependent manner. CsA significantly downregulated the expression of PKM2 in breast cancer cells and decreased adenosine triphosphate (ATP) synthesis, which induced cancer cells to undergo necrosis. Furthermore, the growth suppression effect of CsA was impaired in MCF-7 cells when they were transfected with the PKM2 overexpression plasmid, suggesting that CsA was an effective inhibitor of PKM2-dependent proliferation of breast cancer cells. These results may provide new insights into the mechanism of CsA in cancer therapy.

The clinical value of enzyme-multiplied immunoassay technique monitoring the plasma concentrations of cyclosporine A after renal transplantation

The feasibility and the clinical value of the enzyme-multiplied immunoassay technique (EMIT) monitoring of blood concentrations of cyclosporine A (CsA) in patients treated with CsA were investigated after kidney transplantation. The validation method was performed to the EMIT determination of CsA blood concentration, the CsA whole blood ‘trough concentrations (C₀) of patients in different time periods after renal transplantation were monitored, and combined with the clinical complications, the statistical results were analyzed and compared. EMIT was precise, accurate and stable, also with a high quality control. The mean postoperative blood concentration of CsA was as follows: <1 month, (281.4 ± 57.9)ng/mL; 2 – 3 months, (264.5 ± 41. 2)ng/mL; 4 – 5 months, (236.4 ± 38. 9)ng/mL; 6 – 12 months, (206.5 ± 32.6)ng/mL; >12 months, (185.6 ± 28.1)ng/mL. The toxic reaction rate of CsA blood concentration within the recommended therapeutic concentration was 14. 1%, significantly lower than that of the none-recommended dose group (37.2%) (P < 0.05); the transplantation rejection rate was 4.4%, significantly lower than that of the none-recommended dose group (22.5%) (P < 0.05). Using EMIT to monitor the blood concentration of CsA as the routine laboratory method is feasible, and is able to reduce the CsA toxicity and rejection significantly, leading to achieving the desired therapeutic effect.

Suppression of aberrant transient receptor potential cation channel, subfamily V, member 6 expression in hyperproliferative colonic crypts by dietary calcium

Dietary calcium is believed to reduce colon cancer risk, but the mechanism by which this occurs is poorly understood. Employing the Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model, we previously showed that a high-calcium diet (hCa) significantly abrogated hyperplasia in the distal colons of NIH-Swiss mice. Here, we explored the mechanism of dietary protection by hCa by analyzing the expression of genes involved in the regulation of Ca uptake/flux in the intestinal epithelium, including the Ca-sensing receptor, vitamin D receptor, Ca binding protein, and transient receptor potential cation channels, subfamily V, members 5 and 6 (TRPV5/6). Interestingly, while TRPV6 expression increased significantly during TMCH, the expression of the other gene products was unchanged. This elevated TRPV6 expression was significantly abrogated by a hCa diet. Immunofluorescence revealed apical membrane localization of TRPV6 in the normal colon, whereas during TMCH we observed intense apical pole and cytoplasmic staining along the entire longitudinal crypt axis, including the expanded proliferating zone. The hCa diet reversed this effect. In humans, overexpression of TRPV6 was associated with early-stage colon cancer, and in colon carcinoma cells, inhibition of TRPV6 expression by small interfering RNA inhibited their proliferation and induced apoptosis. TRPV6 small interfering RNA also diminished the transcriptional activity of the calcium-dependent nuclear factors in activated T cells. Thus the aberrant overexpression of TRPV6 contributes to colonic crypt hyperplasia in mice and to colon cancer cell proliferation in humans. Therefore, it is likely that suppression of TRPV6 by a hCa diet is required for its protective effects in the colon.

Suppression of aberrant transient receptor potential cation channel, subfamily V, member 6 expression in hyperproliferative colonic crypts by dietary calcium

Dietary calcium is believed to reduce colon cancer risk, but the mechanism by which this occurs is poorly understood. Employing the Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model, we previously showed that a high-calcium diet (hCa) significantly abrogated hyperplasia in the distal colons of NIH-Swiss mice. Here, we explored the mechanism of dietary protection by hCa by analyzing the expression of genes involved in the regulation of Ca uptake/flux in the intestinal epithelium, including the Ca-sensing receptor, vitamin D receptor, Ca binding protein, and transient receptor potential cation channels, subfamily V, members 5 and 6 (TRPV5/6). Interestingly, while TRPV6 expression increased significantly during TMCH, the expression of the other gene products was unchanged. This elevated TRPV6 expression was significantly abrogated by a hCa diet. Immunofluorescence revealed apical membrane localization of TRPV6 in the normal colon, whereas during TMCH we observed intense apical pole and cytoplasmic staining along the entire longitudinal crypt axis, including the expanded proliferating zone. The hCa diet reversed this effect. In humans, overexpression of TRPV6 was associated with early-stage colon cancer, and in colon carcinoma cells, inhibition of TRPV6 expression by small interfering RNA inhibited their proliferation and induced apoptosis. TRPV6 small interfering RNA also diminished the transcriptional activity of the calcium-dependent nuclear factors in activated T cells. Thus the aberrant overexpression of TRPV6 contributes to colonic crypt hyperplasia in mice and to colon cancer cell proliferation in humans. Therefore, it is likely that suppression of TRPV6 by a hCa diet is required for its protective effects in the colon.