Everolimus with low-dose tacrolimus in simultaneous pancreas and kidney transplantation.

The efficacy and safety of everolimus (EVR) in simultaneous pancreas and kidney transplantation (SPKT) is unclear. We retrospectively evaluated 25 consecutive SPKT recipients at our center from November 2011 to March 2013. All patients received dual induction (Thymoglobulin/basiliximab) and low-dose tacrolimus plus corticosteroids. Nine patients who received EVR were compared with 14 patients who received enteric-coated mycophenolate sodium (EC-MPS); two patients who received sirolimus were excluded from the analysis. With a median follow-up of 14 months, the pancreas graft survival rate was 100% in both groups, and the kidney graft survival rate was 100% and 93% in EVR and EC-MPS patients, respectively. One EC-MPS patient lost her kidney graft from proteinuric kidney disease. Another EC-MPS patient received treatment for clinically diagnosed pancreas and kidney graft rejection. No rejection was observed in EVR patients. Serum creatinine and HbA1c levels were similar between the groups. There was no significant difference of surgical or medical complications. In conclusion, EVR seems to provide comparable short-term outcome to EC-MPS when combined with low-dose tacrolimus/steroids and dual induction therapy. A larger study with a longer follow-up is required to further assess this combination.

Rational design of shepherdin, a novel anticancer agent.

Anticancer agents that selectively kill tumor cells and spare normal tissues are urgently needed. Here, we engineered a cell-permeable peptidomimetic, shepherdin, modeled on the binding interface between the molecular chaperone Hsp90 and the antiapoptotic and mitotic regulator, survivin. Shepherdin makes extensive contacts with the ATP pocket of Hsp90, destabilizes its client proteins, and induces massive death of tumor cells by apoptotic and nonapoptotic mechanisms. Conversely, shepherdin does not reduce the viability of normal cells, and does not affect colony formation of purified hematopoietic progenitors. Systemic administration of shepherdin in vivo is well tolerated, and inhibits human tumor growth in mice without toxicity. Shepherdin could provide a potent and selective anticancer agent in humans.

Developmental control of apoptosis by the immunophilin aryl hydrocarbon receptor-interacting protein (AIP) involves mitochondrial import of the survivin protein.

Survivin is a multifunctional protein with essential roles in cell division and inhibition of apoptosis, but the molecular underpinnings of its cytoprotective properties are poorly understood. Here we show that homozygous deletion of the aryl hydrocarbon receptor-interacting protein (AIP), a survivin-associated immunophilin, causes embryonic lethality in mice by embryonic day 13.5-14, increased apoptosis of Ter119(-)/CD71(-) early erythropoietic progenitors, and loss of survivin expression in its cytosolic and mitochondrial compartments in vivo. In import assays using recombinant proteins, AIP directly mediated the import of survivin to mitochondria, thus enabling its anti-apoptotic function, whereas a survivin 1-141 mutant that does not bind AIP was not imported to mitochondria and failed to inhibit apoptosis. AIP-directed mitochondrial import of survivin did not affect cell division, was independent of the organelle transmembrane potential, did not require the chaperone Heat Shock Protein 90 (Hsp90), and was inhibited by cytosolic factor(s) present in normal cells. shRNA knockdown of the mitochondrial import receptor Tom20 abolished mitochondrial import of survivin and sensitized tumor cells to apoptosis, whereas silencing of Tom70 had no effect. Therefore, an AIP-Tom20 recognition contributes to cell survival in development and cancer by mediating the mitochondrial import of survivin.

Aberrant overexpression of the cell polarity module scribble in human cancer.

Human Scribble (Scrib) is an evolutionary-conserved cell polarity protein, but its potential role in human cancer is controversial. Herein, we show that Scrib is nearly universally overexpressed in cultured tumor cell lines and genetically disparate cancer patient series compared with matched normal tissues in vivo. Instead of a membrane association seen in normal epithelia, tumor-associated Scrib is mislocalized and found predominantly in the cytosol. Small-interfering RNA silencing of Scrib in model lung adenocarcinoma A549 cells inhibited cell migration in wound-healing assays, suppressed tumor cell invasion across Matrigel-coated inserts, and down-regulated the expression of cell motility markers and mediators of epithelial-mesenchymal transition. These data uncover a previously unrecognized exploitation of Scrib for aberrant tumor cell motility and invasion, thus potentially contributing to disease progression in humans.

Renal Protective Effect of Everolimus in Liver Transplantation: A Prospective Randomized Open-Label Trial.

Renal dysfunction is associated with poor long-term outcomes after liver transplantation. We examined the renal sparing effect of everolimus (EVR) compared to standard calcineurin inhibitor (CNI) immunosuppression with direct measurements of renal function over 24 months. METHODS: This was a prospective, randomized, open-label trial comparing EVR and mycophenolic acid (MPA) with CNI and MPA immunosuppression. An Investigational New Drug Application (IND # 113882) was obtained with the Food and Drug Administration as EVR is only approved for use with low-dose tacrolimus. Serum creatinine, 24-hour urine creatinine clearance, iothalamate clearance, Cockcroft-Gault creatinine clearance (CrCl), and Modification of Diet in Renal Disease estimated glomerular filtration rate were prospectively measured at 4 study visits. Nonparametric statistical tests were used for analyses, including the Mann-Whitney U test for continuous outcomes and Pearson's chi-square test for binary outcomes. Effect size was measured using Cohen's d. Patients also completed quality of life surveys using the FACT-Hep instrument at each study visit. Comparison between the 2 groups was performed using the Student t test. RESULTS: Each arm had 12 subjects; 4 patients dropped out in the EVR arm and 1 in the CNI arm by 24 months. Serum creatinine (P = 0.015), Modification of Diet in Renal Disease estimated glomerular filtration rate (P = 0.013), and 24-hour urine CrCL (P = 0.032) were significantly better at 24 months with EVR. Iothalamate clearance showed significant improvement at 12 months (P = 0.049) and a trend toward better renal function (P = 0.099) at 24 months. There was no statistical significance with Cockcroft-Gault CrCl. Adverse events were not significantly different between the 2 arms. The EVR group also showed significantly better physical, functional, and overall self-reported quality of life (P = 0.01) at 24 months. CONCLUSIONS: EVR with MPA resulted in significant long-term improvement in renal function and quality of life at 24 months after liver transplantation compared with standard CNI with MPA immunosuppression.

Incidence of Post-Liver Transplant Hepatic Dysfunction After Sustained Virologic Response Following Direct-Acting Anti-Hepatitis C Therapy.

OBJECTIVES: Newly developed, direct-acting antiviral therapy is effective in over 90% of cases to eradicate hepatitis C virus infection. Direct-acting antiviral therapy is also effective in liver transplant recipients with recurrent hepatitis C virus infection. However, hepatic function after sustained virologic response in transplant recipients is unknown. Here, we aimed to uncover the incidence of hepatic dysfunction in this patient group at our center. MATERIALS AND METHODS: Our study included 40 consecutive (January 2014 to February 2016) and compliant posttransplant recipients who achieved sustained viral response from direct-acting antiviral therapy. Patients were investigated for incidence and causes of hepatic dysfunction. RESULTS: In our patient group, 4 (10%) experienced hepatic dysfunction with stable baseline immunosuppression, with 2 having drastic increases in alanine aminotransferase at 15 and 32 weeks after direct-acting antiviral therapy. Biopsies showed hepatitis, and both patients were treated with hydrocortisone, which increased their baseline immunosuppression. The 3rd patient had an increase in bilirubin at 21 weeks posttherapy, with biopsy showing macrovascular steatosis. The 4th patient had a rapid increase in bilirubin at 7 weeks after direct-acting antiviral therapy, with biopsy showing significant duct loss. CONCLUSIONS: During the study period, 10% of patients experienced hepatic dysfunction after sustained viral response. Presumed causative factors included partial immune reconstitution and nonalcoholic fatty liver disease.

Is there increased risk of hepatocellular carcinoma recurrence in liver transplant patients with direct-acting antiviral therapy?

BACKGROUND: Recently, a controversy has emerged: is the rate of recurrence of hepatocellular carcinoma (HCC) higher following treatment of hepatitis C virus (HCV) with direct-acting antiviral (DAA) therapy? However, the risk of HCC recurrence has not been studied in liver transplant (LTx) recipients who received DAA therapy. The aim of the present study is to compare the rate of HCC recurrence in LTx recipients who did or did not receive DAA therapy. PATIENTS AND METHODS: Sixty-three patients received LTx with HCC. Twenty-seven (42.9%) with HCV received DAA therapy (Group A), 20 (31.7%) with HCV did not receive DAA therapy (Group B), and 16 (25.4%) did not have HCV (Group C). RESULTS: In group A, three (11%), in group B, one (5%), and in group C, none had recurrence of HCC. Actuarial 4-year recurrence-free survival was 88.9, 95, and 100% in group A, B, and C, respectively (p = 0.37). Group A was subdivided into two groups for comparison with Group B: A1 included five patients who had end of treatment response (ETR) without sustained virological response (SVR), and A2 included 20 patients who achieved SVR. Three patients from A1 had HCC recurrence and no patients from A2 had HCC recurrence. (p = 0.0038; group A1, A2, and B). CONCLUSIONS: The rate of HCC recurrence in LTx patients with DAA therapy was significantly higher with ETR, without SVR, after DAA therapy compared to patients with SVR or patients who did not receive DAA therapy. LTx recipients with HCC receiving DAA therapy requires further studies.

Activated checkpoint kinase 2 provides a survival signal for tumor cells.

Tumor cells often become resistant to DNA damage-based therapy; however, the underlying mechanisms are not yet understood. Here, we show that tumor cells exposed to DNA damage counteract cell death by releasing the antiapoptotic protein, survivin, from mitochondria. This is independent of p53, and requires activated checkpoint kinase 2 (Chk2), a putative tumor suppressor. Molecular or genetic targeting of Chk2 prevents the release of survivin from mitochondria, enhances DNA damage-induced tumor cell apoptosis, and inhibits the growth of resistant in vivo tumors. Therefore, activated Chk2 circumvents its own tumor-suppressive functions by promoting tumor cell survival. Inhibiting Chk2 in combination with DNA-damaging agents may provide a rational approach for treating resistant tumors.

Mitochondrial survivin inhibits apoptosis and promotes tumorigenesis.

Evasion of apoptosis is a hallmark of cancer, but the molecular circuitries of this process are not understood. Here we show that survivin, a member of the inhibitor of apoptosis gene family that is overexpressed in cancer, exists in a novel mitochondrial pool in tumor cells. In response to cell death stimulation, mitochondrial survivin is rapidly discharged in the cytosol, where it prevents caspase activation and inhibits apoptosis. Selective targeting of survivin to mitochondria enhances colony formation in soft agar, accelerates tumor growth in immunocompromised animals, and abolishes tumor cell apoptosis in vivo. Therefore, mitochondrial survivin orchestrates a novel pathway of apoptosis inhibition, which contributes to tumor progression.

Oncolytic recombinant herpes simplex virus for treatment of orthotopic liver tumors in nude mice.

Cell-specific, replicating viruses are being developed as a new class of oncolytic agents. A novel approach to viral gene therapy with the use of replication-competent herpes simplex virus has been described; G92A is a replication-competent, multimutant oncolytic herpes simplex virus (HSV) that has been evaluated for anticancer effects and selectivity in the treatment of subcutaneous tumors. G92A replicates efficiently in albumin-producing tumor cell lines but not in non-albumin-producing tumor cell lines, whereas both types are equally susceptible to a non-tissue-specific recombinant HSV, hrR3. In this study, we analyzed the antitumoral efficacy of a single intrasplenic G92A or hrR3 injection in nude mice. In vivo, G92A replicated well in liver xenografts of human albumin-producing hepatoma cells (Hep3B) but not in liver xenografts of a non-albumin-producing malignant colon tumor cell line (HT29), whereas hrR3 replicated well in both tumor types. G92A effectively and selectively replicated throughout liver tumors without apparent hepatotoxicity and inhibited tumor growth, leading to a significantly increased survival time. By monitoring lacZ histochemical staining, we determined the oncolytic potential of recombinant HSV against liver tumors. Our results indicate that G92A warrants further investigation as a clinical therapy against malignant liver tumors.

Therapeutic targeting of the survivin pathway in cancer: initiation of mitochondrial apoptosis and suppression of tumor-associated angiogenesis.

PURPOSE: Molecular antagonists of the inhibitor of apoptosis protein survivin have shown promise as novel anticancer strategies for triggering tumor cell apoptosis, dysregulating mitotic progression, and inhibiting tumor growth in preclinical models. However, how survivin couples to the cell death machinery has remained elusive, and the relevant cellular targets of survivin antagonists have not been completely elucidated. EXPERIMENTAL DESIGN: Human umbilical vein and dermal microvascular endothelial cells were infected with replication-deficient adenoviruses encoding survivin (pAd-Survivin), green fluorescent protein (pAd-GFP), or a phosphorylation-defective survivin Thr(34)-->Ala (pAd-T34A) dominant negative mutant. The effect of wild-type or mutant survivin was investigated on capillary network stability, endothelial cell viability, and caspase activation in vitro and on kinetics of tumor growth and development of angiogenesis in a breast cancer xenograft model in vivo. The cell death pathway initiated by survivin targeting was mapped with respect to cytochrome c release, changes in mitochondrial transmembrane potential, and apoptosome requirements using mouse embryonic fibroblasts deficient in Apaf-1 or caspase-9. RESULTS: Adenoviral transduction of endothelial cells with pAd-Survivin inhibited growth factor deprivation- or ceramide-induced apoptosis, reduced caspase-3 and -7 generation, and stabilized three-dimensional capillary networks in vitro. Conversely, expression of pAd-T34A caused apoptosis in umbilical vein and dermal microvascular endothelial cells and resulted in caspase-3 activity. Cell death induced by survivin targeting exhibited the hallmarks of mitochondrial-dependent apoptosis with release of cytochrome c and loss of mitochondrial transmembrane potential and was suppressed in Apaf-1 or caspase-9 knockout mouse embryonic fibroblasts. When injected in human breast cancer xenografts, pAd-T34A inhibited growth of established tumors and triggered tumor cell apoptosis in vivo. This was associated with a approximately 60% reduction in tumor-derived blood vessels by quantitative morphometry of CD31-stained tumor areas, and appearance of endothelial cell apoptosis by internucleosomal DNA fragmentation in vivo. CONCLUSIONS: Survivin functions as a novel upstream regulator of mitochondrial-dependent apoptosis, and molecular targeting of this pathway results in anticancer activity via a dual mechanism of induction of tumor cell apoptosis and suppression of angiogenesis.

Transcriptional expression of survivin and its splice variants in brain tumors in humans.

OBJECT: Survivin, one of the apoptosis inhibitor proteins, has been detected in most cancers in humans. In addition, two splice variants (survivin-2B and survivin-deltaEx3) have been identified. The authors investigated the transcription levels of survivin messenger (m)RNA and its splice variants in nine tumor cell lines, including gliomas, and in 25 brain tumor samples, by performing quantitative reverse transcription-polymerase chain reaction. The correlation between transcript expression levels and pathological findings were also analyzed. METHODS: Transcription levels were measured using primer pairs specific for survivin and either of its splice variants and were normalized to the glyceraldehyde 6-phosphate dehydrogenase. Among the tumor cell lines tested, glioblastoma cell lines showed the highest levels of survivin expression. Among brain tumor samples studied, survivin was preferentially expressed in malignant brain tumors and gliomas. The relative expression level of survivin-deltaEx3/survivin was significantly higher in malignant than in benign brain tumor samples. Expression patterns were dominant for survivin-deltaEx3 in malignant brain tumors and dominant for survivin-2B in benign ones. A significant linear correlation between survivin mRNA expression and MIB-1 labeling index was demonstrated in all brain tumor samples. CONCLUSIONS: The authors' results indicate that quantifying the levels of survivin and its splice variants is useful for the prediction of the cell biological malignancy of gliomas, independent of their pathological features.

Relationship between types of common channel and development of biliary tract cancer in pancreaticobiliary maljunction.

BACKGROUND/AIMS: The incidence of biliary tract cancer development is high among patients with pancreaticobiliary maljunction. However, there have been no reports published evaluating the incidence of development of biliary tract cancers in pancreaticobiliary maljunction based on the morphology of the common channel at the junction of the bile and pancreatic ducts. We evaluated between types of common channel and development of biliary tract cancers in pancreaticobiliary maljunction. METHODOLOGY: During the last 21 years, we have experienced 78 patients with pancreaticobiliary maljunction. Of those patients, 44 adult patients, whose morphologic types of common channel were identified by cholangiography, were enrolled in this study. The dilatation patterns of the common channel were classified into 3 types: A type (moderately dilated type), B type (markedly dilated type), and C type (non-dilated type). Evaluated items included the length and dilation patterns of the common channel, incidence of development of biliary tract cancers and proliferative activity in the biliary tract epithelium. RESULTS: Seventeen patients had a common channel shorter than 20 mm, while 27 had a common channel of 20 mm or longer. Eleven patients with a common channel of 20 mm or longer had development of bile tract cancers. The dilation patterns of the common channel were classified as A (11 patients), B (16 patients) and C type (17 patients). Amylase levels in the biliary tract were higher in patients with A and B type than in patients with the C type. Development of gallbladder cancer was observed in 6 patients with A, 2 patients with B and one patient with C, while development of bile duct cancer was observed in 2 patients with C and one patient with B. The PCNAL.I. of the biliary epithelium was higher in patients with A, B and C type in descending order. CONCLUSIONS: The incidence of development of biliary tract cancer was higher in patients with common channel of 20 mm or longer. The proliferative activity in the biliary epithelium was accelerated in patients with A type, together with a high incidence of development of gallbladder cancer.

Studies on biliary tract carcinoma in the case with pancreaticobiliary maljunction.

BACKGROUND/AIMS: The purpose of this study was to clarify the clinicopathological features of pancreaticobiliary maljunction and to determine the appropriate surgical approach for biliary tract with pancreaticobiliary maljunction. METHODOLOGY: The data of 77 patients with pancreaticobiliary maljunction including 13, who had been treated for biliary tract cancer, were reviewed retrospectively. We assessed the clinical features, biological characteristics of the cancer, methods of surgical treatment, postoperative outcome and cell proliferating activity of the biliary epithelium, evaluated by the PCNALI (proliferating cell nuclear antigen-labeling index). RESULTS: The incidence of cancer development in the case with pancreaticobiliary maljunction was 13.4% in the bile duct dilatation group (n = 67) and 40.0% in the non-dilatation group (n = 10). Dissection of lymphadenectomy was performed in 10 (76.9%) of 13 patients, and curative resection was feasible in 9 of the 10 patients. Two (20.0%) of the 10 patients had lymph node involvement noted at surgery and died of recurrence. In the other eight patients without lymph node involvement at surgery, six patients underwent curative resection and are alive at 7 months to 11 years and 6 months after surgery. PCNALI of the biliary epithelium of the patients with pancreaticobiliary maljunction was significantly higher than that of the control group. CONCLUSIONS: For patients with pancreaticobiliary maljunction, it should be stressed that the extrahepatic bile duct be prophylactically removed, even when there are no neoplasmatic changes because of high prevalence of cancer development, presumably predicted by the increase of cell proliferative activity in the biliary epithelium. For patients with biliary cancer, early detection at the stage with no lymph node involvement is essential to secure for long-term survival.

Lack of clinical association and effect of peripheral WBC counts on immune cell function test in kidney transplant recipients with T-cell depleting induction and steroid-sparing maintenance therapy.

The Cylex ImmuKnow assay measures the amount of stimulated ATP production by CD4+ T-cells, and has been used clinically, trying to predict rejection and infection episodes. However, predictive values of this assay after induction therapy with steroid-sparing maintenance protocols are unclear. In this single-center cohort study, we analyzed renal transplant recipients who received T-cell depleting+/-anti-IL2 receptor antibodies and tacrolimus/mycophenolate maintenance without steroids. A total of 4224 ImmuKnow levels in 306 patients were available for analysis. ImmuKnow levels (Mean ± SE) changed over time after induction therapy with a paradoxical initial increase: 419 ± 23, 461 ± 32, 519 ± 14, 411 ± 10, 344 ± 6, and 405 ± 3 for pre-transplant, 0-1 wk, 1 wk-1 mo, 1-3 mos, 3 mos-1 yr, and thereafter. This change was parallel to the evolution of peripheral WBC counts and ImmuKnow levels had weak but significant correlation with WBC counts (R(2)=0.264, P<0.0001). The levels for biopsy-proven rejection (389 ± 56) and borderline/clinical rejection (254 ± 41) were not significantly higher than the levels of quiescent patients. The levels for opportunistic infection (349 ± 48) and other infections (345 ± 27) were not significantly lower than the levels of quiescent patients. The longitudinal changes in ImmuKnow levels were not predictive of rejection or infection. In conclusion, ImmuKnow levels can vary after T-cell depleting induction therapies at various time points, even without significant clinical events. Since ImmuKnow levels seem to be affected by WBC counts, ImmuKnow results need to be interpreted with caution. The effects of leukocytosis or leukopenia caused by immunosuppressive medication on the ImmuKnow assay need further investigation.

Control of tumor bioenergetics and survival stress signaling by mitochondrial HSP90s.

Tumors successfully adapt to constantly changing intra- and extracellular environments, but the wirings of this process are still largely elusive. Here, we show that heat-shock-protein-90-directed protein folding in mitochondria, but not cytosol, maintains energy production in tumor cells. Interference with this process activates a signaling network that involves phosphorylation of nutrient-sensing AMP-activated kinase, inhibition of rapamycin-sensitive mTOR complex 1, induction of autophagy, and expression of an endoplasmic reticulum unfolded protein response. This signaling network confers a survival and proliferative advantage to genetically disparate tumors, and correlates with worse outcome in lung cancer patients. Therefore, mitochondrial heat shock protein 90s are adaptive regulators of tumor bioenergetics and tractable targets for cancer therapy.

Chk2 phosphorylation of survivin-DeltaEx3 contributes to a DNA damage-sensing checkpoint in cancer.

Survivin is an oncogene that functions in cancer cell cytoprotection and mitosis. Here we report that differential expression in cancer cells of a C-terminal splice variant of survivin, termed survivin-ΔEx3, is tightly associated with aggressive disease and markers of unfavorable prognosis. In contrast to other survivin variants, survivin-ΔEx3 localized exclusively to nuclei in tumor cells and was phosphorylated at multiple residues by the checkpoint kinase Chk2 during DNA damage. Mutagenesis of the Chk2 phosphorylation sites enhanced the stability of survivin-ΔEx3 in tumor cells, inhibited the expression of phosphorylated H2AX (γH2AX) in response to double-strand DNA breaks, and impaired growth after DNA damage. DNA damage induced Chk2 phosphorylation, stabilization of p53, induction of the cyclin-dependent kinase inhibitor p21, and homologous recombination-induced repair were not affected. In vivo, active Chk2 was detected at the earliest stages of the colorectal adenoma-to-carcinoma transition, persisted in advanced tumors, and correlated with increased survivin expression. Together, our findings suggest that Chk2-mediated phosphorylation of survivin-ΔEx3 contributes to a DNA damage-sensing checkpoint that may affect cancer cell sensitivity to genotoxic therapies.

Essential role of the small GTPase Ran in postnatal pancreatic islet development.

The small GTPase Ran orchestrates pleiotropic cellular responses of nucleo-cytoplasmic shuttling, mitosis and subcellular trafficking, but whether deregulation of these pathways contributes to disease pathogenesis has remained elusive. Here, we generated transgenic mice expressing wild type (WT) Ran, loss-of-function Ran T24N mutant or constitutively active Ran G19V mutant in pancreatic islet ß cells under the control of the rat insulin promoter. Embryonic pancreas and islet development, including emergence of insulin(+) ß cells, was indistinguishable in control or transgenic mice. However, by one month after birth, transgenic mice expressing any of the three Ran variants exhibited overt diabetes, with hyperglycemia, reduced insulin production, and nearly complete loss of islet number and islet mass, in vivo. Deregulated Ran signaling in transgenic mice, adenoviral over-expression of WT or mutant Ran in isolated islets, or short hairpin RNA (shRNA) silencing of endogenous Ran in model insulinoma INS-1 cells, all resulted in decreased expression of the pancreatic and duodenal homeobox transcription factor, PDX-1, and reduced ß cell proliferation, in vivo. These data demonstrate that a finely-tuned balance of Ran GTPase signaling is essential for postnatal pancreatic islet development and glucose homeostasis, in vivo.

Exploiting the mitochondrial unfolded protein response for cancer therapy in mice and human cells.

Fine tuning of the protein folding environment in subcellular organelles, such as mitochondria, is important for adaptive homeostasis and may participate in human diseases, but the regulators of this process are still largely elusive. Here, we have shown that selective targeting of heat shock protein-90 (Hsp90) chaperones in mitochondria of human tumor cells triggered compensatory autophagy and an organelle unfolded protein response (UPR) centered on upregulation of CCAAT enhancer binding protein (C/EBP) transcription factors. In turn, this transcriptional UPR repressed NF-κB-dependent gene expression, enhanced tumor cell apoptosis initiated by death receptor ligation, and inhibited intracranial glioblastoma growth in mice without detectable toxicity. These data reveal what we believe to be a novel role of Hsp90 chaperones in the regulation of the protein-folding environment in mitochondria of tumor cells. Disabling this general adaptive pathway could potentially be used in treatment of genetically heterogeneous human tumors.

Heat shock protein 60 regulation of the mitochondrial permeability transition pore in tumor cells.

Mitochondrial apoptosis plays a critical role in tumor maintenance and dictates the response to therapy in vivo; however, the regulators of this process are still largely elusive. Here, we show that the molecular chaperone heat shock protein 60 (Hsp60) directly associates with cyclophilin D (CypD), a component of the mitochondrial permeability transition pore. This interaction occurs in a multichaperone complex comprising Hsp60, Hsp90, and tumor necrosis factor receptor-associated protein-1, selectively assembled in tumor but not in normal mitochondria. Genetic targeting of Hsp60 by siRNA triggers CypD-dependent mitochondrial permeability transition, caspase-dependent apoptosis, and suppression of intracranial glioblastoma growth in vivo. Therefore, Hsp60 is a novel regulator of mitochondrial permeability transition, contributing to a cytoprotective chaperone network that antagonizes CypD-dependent cell death in tumors.