Expression of the 100-kda glucose-regulated protein (GRP100/endoplasmin) is associated with tumorigenicity in a model of rat colon adenocarcinoma

GM2-GM3 gangliosides ratio is dependent on GRP94 through down-regulation of GM2-AP cofactor in brain metastasis cells

GRP94 is an ATP-dependent chaperone able to regulate pro-oncogenic signaling pathways. Previous studies have shown a critical role of GRP94 in brain metastasis (BrM) pathogenesis and progression. In this work, an untargeted lipidomic analysis revealed that some lipid species were altered in GRP94-deficient cells, specially GM2 and GM3 gangliosides. The catalytic pathway of GM2 is affected by the low enzymatic activity of β-Hexosaminidase (HexA), responsible for the hydrolysis of GM2 to GM3. Moreover, a deficiency of the GM2-activator protein (GM2-AP), the cofactor of HexA, is observed without alteration of gene expression, indicating a post-transcriptional alteration of GM2-AP in the GRP94-ablated cells. One plausible explanation of these observations is that GM2-AP is a client of GRP94, resulting in defective GM2 catabolic processing and lysosomal accumulation of GM2 in GRP94-ablated cells. Overall, given the role of gangliosides in cell surface dynamics and signaling, their imbalance might be linked to modifications of cell behaviour acquired in BrM progression. This work indicates that GM2-AP could be an important factor in ganglioside balance maintenance. These findings highlight the relevance of GM3 and GM2 gangliosides in BrM and reveal GM2-AP as a promising diagnosis and therapeutic target in BrM research.

CD147 induces UPR to inhibit apoptosis and chemosensitivity by increasing the transcription of Bip in hepatocellular carcinoma

The unfolded protein response (UPR) is generally activated in solid tumors and results in tumor cell anti-apoptosis and drug resistance. However, tumor-specific UPR transducers are largely unknown. In the present study, we identified CD147, a cancer biomarker, as an UPR inducer in hepatocellular carcinoma (HCC). The expression of the major UPR target, Bip, was found to be positively associated with CD147 in human hepatoma tissues. By phosphorylating FAK and Src, CD147-enhanced TFII-I tyrosine phosphorylation at Tyr248. CD147 also induced p-TFII-I nuclear localization and binding to the Bip promoter where endoplasmic reticulum (ER) stress response element 1 (ERSE1) (-82/-50) is the most efficient target of the three ERSEs, thus increasing transcription of Bip. Furthermore, by inducing UPR, CD147 inhibited HCC cell apoptosis and decreased cell Adriamycin chemosensitivity, thus decreasing the survival rate of hepatoma-bearing nude mice. Together, these results reveal pivotal roles for CD147 in modulating the UPR in HCC and raise the possibility that CD147 is a target that promotes HCC cell apoptosis and increases the sensitivity of tumors to anti-cancer drugs. Therefore, CD147 inhibition provides an opportunity to enhance the efficacy of existing agents and represents a novel target for HCC treatment.

Glycoproteomics of paclitaxel resistance in human epithelial ovarian cancer cell lines: towards the identification of putative biomarkers

Glycosylation, one of the most common post translational modifications (PTMs) of proteins, is often associated with carcinogenesis and tumor malignancy. Ovarian cancer is the sixth cause of cancer-related death in Western countries. Currently, it is treated by debulking surgery followed by chemotherapy based on paclitaxel, alone or in combination with other drugs. However, chemoresistance represents a major obstacle to positive clinical outcome. We used two approaches, Multiplexed Proteomics (MP) technology and Multilectin Affinity Chromatography (MAC) to characterize the glycoproteome of the human ovarian cancer cell line A2780 and its paclitaxel resistant counterpart A2780TC1. Furthermore proteins were separated by traditional 2DE or DIGE and identified by MS (MALDI TOF or LC MS/MS). Seventy glycoproteins were successfully identified in ovarian cancer cells and 10 were found to be differentially expressed between sensitive and resistant cell lines. We focused on four glycoproteins (tumor rejection antigen (gp96) 1, triose phosphate isomerase, palmitoyl-protein thioesterase 1 precursor and ER-associated DNAJ) which were remarkably upregulated in A2780TC1 compared to A2780 cell line and which may represent biomarkers for paclitaxel resistance in ovarian cancer.

Honokiol induces calpain-mediated glucose-regulated protein-94 cleavage and apoptosis in human gastric cancer cells and reduces tumor growth

BACKGROUND

Honokiol, a small molecular weight natural product, has been shown to possess potent anti-neoplastic and anti-angiogenic properties. Its molecular mechanisms and the ability of anti-gastric cancer remain unknown. It has been shown that the anti-apoptotic function of the glucose-regulated proteins (GRPs) predicts that their induction in neoplastic cells can lead to cancer progression and drug resistance. We explored the effects of honokiol on the regulation of GRPs and apoptosis in human gastric cancer cells and tumor growth.

METHODOLOGY AND PRINCIPAL FINDINGS

Treatment of various human gastric cancer cells with honokiol led to the induction of GRP94 cleavage, but did not affect GRP78. Silencing of GRP94 by small interfering RNA (siRNA) could induce cell apoptosis. Treatment of cells with honokiol or chemotherapeutics agent etoposide enhanced the increase in apoptosis and GRP94 degradation. The calpain activity and calpain-II (m-calpain) protein (but not calpain-I (micro-calpain)) level could also be increased by honokiol. Honokiol-induced GRP94 down-regulation and apoptosis in gastric cancer cells could be reversed by siRNA targeting calpain-II and calpain inhibitors. Furthermore, the results of immunofluorescence staining and immunoprecipitation revealed a specific interaction of GRP94 with calpain-II in cells following honokiol treatment. We next observed that tumor GRP94 over-expression and tumor growth in BALB/c nude mice, which were inoculated with human gastric cancer cells MKN45, are markedly decreased by honokiol treatment.

CONCLUSIONS AND SIGNIFICANCE

These results provide the first evidence that honokiol-induced calpain-II-mediated GRP94 cleavage causes human gastric cancer cell apoptosis. We further suggest that honokiol may be a possible therapeutic agent to improve clinical outcome of gastric cancer.

Pharmacoproteomics study of cetuximab in nasopharyngeal carcinoma

Epidermal growth factor receptor (EGFR) is usually overexpressed in nasopharyngeal carcinoma (NPC). Our recent in vitro study has demonstrated that cetuximab (an antibody drug against EGFR) inhibits the growth of NPC cell lines, HK1 and HONE-1. The present study investigates the effect of cetuximab on protein expressions of NPC cell lines. NPC cells were cultured in the absence or presence of cetuximab at the IC50 concentrations (3 nM for HK1 and 0.3 nM for HONE-1) for 48 h, and total cell lysates were extracted. The cell lysates were then subjected to two-dimensional polyacrylamide gel electrophoresis (2D PAGE), and the 2D gel images were compared to discover the protein changes caused by cetuximab treatment. The common differentially expressed proteins in NPC cell lines were identified by peptide mass fingerprinting. We found that heat shock protein gp96 was down-regulated, while alpha-enolase, tumor suppressor protein maspin, and p97 valosin containing protein were up-regulated after cetuximab treatment. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed that the changes in protein levels of gp96, maspin, and p97 coincided with mRNA levels, indicating that these proteins were regulated at transcriptional levels. Up-regulation of gp96 has been observed in various cancers and reported to have tumor protective effects. P97 is a multifunctional AAA (ATPase associated with a variety of activities) protein and is involved in numerous cellular activities including membrane transport, protein folding, protein degradation, and cell division. Maspin has been shown to increase apoptosis, and block the growth, invasion, and metastatic properties of many tumors. The comparative tumor suppression effects of cetuximab and maspin suggest that cetuximab might exert its antitumor effects partly by up-regulation of maspin expression. The study also indicates that proteomic analysis is a promising approach to elucidate the functional mechanisms of anticancer drugs. Pharmacoproteomic study may also help to identify clinical responders for drug treatment and provide insight for new drug development.

The unfolded protein response and cancer: a brighter future unfolding?

Mammalian cells are bathed in an interstitial fluid that has a tightly regulated composition in healthy states. Interstitial fluid provides cells with all the necessary metabolic substrates (oxygen, glucose, amino acids, etc.), and waste molecules are removed by diffusion gradients that are controlled by local vascular perfusion. The health and normal function of all cells within a body is dependent on the maintenance of this microenvironment. However, many disease states cause fluctuations in this, and in some instances, these might be of sufficient severity to stress and/or be toxic to the cell. Cells have developed a number of responses to enable their survival in a hostile environment. This article discusses one such pathway--the unfolded protein response and its relationship to cancer. The molecular signalling cascade, the mechanism of its activation in cancer and the consequences of its activation for a tumour are discussed, as are clinical studies and potential translational approaches for utilising this pathway for tumour targeting.

Expression of stress response protein glucose regulated protein-78 mediated by c-Myb

Glucose regulated protein-78, GRP78 has been implicated in the protection of tumor cells from cytotoxic damage and apoptosis. When protein profiles of colon cell lines were investigated we found remarkably high GRP78 expression in two cell lines. These cell lines express elevated levels of the transcription factor c-Myb due to genomic amplification of the c-myb locus and we hypothesized that c-Myb regulates GRP78 expression in colon cancer cells. The promoters of human and murine GRP78 and the related family member GRP94 were examined and potential c-Myb binding sites were identified and characterized. DNA binding studies with recombinant c-Myb and nuclear extracts together with ChIP assays on colon cell lines validated these sites. Endogenous GRP78 expression was further induced in these colon cells in response to Thapsigargin treatment, a potent inducer of the unfolded protein response. Transactivation studies with the human GRP78 promoter in colon cell lines showed reporter activity was dependent upon the presence of a conserved c-Myb binding site independent of sequences associated with the unfolded protein response. Finally, over-expression of c-Myb induced the endogenous GRP78 gene. These data suggest that amplification of c-myb in tumor cells may lead to robust GRP78 gene induction, which may in turn assist cells in survival under conditions of oxygen deprivation and nutrient stress.

Overexpression of endoplasmic reticulum molecular chaperone GRP94 and GRP78 in human lung cancer tissues and its significance

BACKGROUND

To investigate the relationship between the expression of glucose-regulated protein94 (GRP94) and GRP78 at the level of mRNA and protein in vivo and in human lung cancer.

METHODS

RT-PCR, real-time PCR, immunohistochemistry and/or Western blot were used in 54 cases of lung cancer and corresponding normal lung tissue.

RESULTS

The expression pattern of GRP94 and GRP78 was similar. There was a significant overexpression of GRP94 and GRP78 at both mRNA and protein levels in cancer tissues as compared to normal tissues. The relative levels of GRP94 and GRP78 mRNA evaluated by RT-PCR in cancer and normal lung tissue were: GRP94: 3.48+/-2.06 versus 2.01+/-1.83; GRP78: 3.64+/-1.87 versus 2.21+/-1.54; by real-time PCR were: GRP94: 2.89+/-0.64 versus 1.12+/-0.54; GRP78: 2.56+/-0.82 versus 0.96+/-0.42. The relative level of GRP94 and GRP78 protein by Western blot in cancer and normal lung tissue were: GRP94: 3.46+/-1.72 versus 1.81+/-0.92; GRP78: 4.84+/-2.55 versus 1.91+/-1.15, indicating an approximate 2-fold and a 3-fold increase in GRP94 and GRP78 protein in cancer tissue as compared with normal tissue. Immunohistochemistry result for GRP94 and GRP78 in cancer and normal tissue was similar, that is: a stronger stain was observed in cancer tissue (main intensity of staining ++ to +++) compared to normal tissue (main intensity of staining + to ++). All the difference for GRP94 and GRP78 between the two tissues were significant (p<0.05). Furthermore, the overexpression of GRP94 and GRP78 in the cancer tissue correlated with grade of differentiation and stage of tumors. There was stronger expression in poorly differentiated tumors than in well-moderately differentiated tumors (p<0.05). There was also stronger expression in stage III than in stages I and II tumors (p<0.05). No statistically significant differences were found among various pathologic types of tumors. Correlation analysis showed that there is a positive correlation between GRP94 and GRP78.

CONCLUSION

The expression pattern of GRP94 and GRP78 was similar in human lung cancer. They both were related with the differentiation and progression of the cancer. The expression at mRNA and protein level may be valuable in evaluating the grade of differentiation and clinical stage of human lung cancer.

Significant correlation between expression level of HSP gp96 and progression of hepatitis B virus induced diseases

AIM: Gp96, also known as Grp94, is a member of heat shock protein (HSP) family and binds repertoires of peptides thereof eliciting peptide-specific T cell immune responses. It predominantly locates inside the endoplasmic reticulum (ER) with some cell surface expression in certain cancerous cells. Previous studies have shown that gp96 expression level was up-regulated in tumor cells, including hepatocellular carcinoma (HCC). However, relationship between the extent of gp96 expression and disease progression especially HBV-induced chronic infection, cirrhosis and hepatocellular carcinoma, has not been addressed before. As primary HCC can be induced and progressed from chronic hepatitis B virus (HBV) infection and HBV-induced cirrhosis, we designed an immunohistochemical experiment to test the correlation between gp96 expression level and HBV-induced disease progression, from chronic HBV infection, cirrhosis to HCC.

METHODS: We chose liver samples from different patients of hepatitis B virus induced diseases, including chronic hepatitis B (77 patients), cirrhosis (27 patients) and primary HCC (30 patients), to test the expression level of gp96 in different affected groups. Formalin-fixed, and paraffin-embedded liver tissues taken from these patients were immuno-stained by using an anti-gp96 monoclonal antibody for the expression level of gp96 protein in the sections. In addition, Western blotting of whole cell lysates derived from established human embryonic liver cell lines and several human HCC cell lines (Huh7, HepG2, SSMC-7721) was compared with the expression of gp96.

RESULTS: We found that the extent of elevated gp96 expression was significantly correlated with the disease progression, and was the highest in HCC patients, lowest in chronic HBV infection and was that of the cirrhosis in the middle.

CONCLUSION: Increased expression of gp96 might be used as a diagnostic or prognostic bio-marker for the HBV infection and HBV-induced diseases.

A cellular UDP-glucose deficiency causes overexpression of glucose/oxygen-regulated proteins independent of the endoplasmic reticulum stress elements

A low level of UDP-Glc occurs in cells exposed to hypoxia or glucose starvation. This work reveals that a 65% reduction in the cellular UDP-Glc level causes up-regulation of the mitochondrial chaperone GRP75 and the endoplasmic reticulum (ER) resident chaperones GRP58, ERp72, GRP78, GRP94, GRP170, and calreticulin. Conditions that cause misfolding of proteins within the ER activate the transcription factors ATF6alpha/beta and induce translation of the transcription factors XBP-1/TREB5 and ATF4/CREB2. These transcription factors induce the overexpression of ER chaperones and CHOP/GADD153. However, the 65% decrease in the cellular UDP-Glc level does not cause activation of ATF6alpha, splicing of XBP-1/TREB5, induction of ATF4/CREB2, or expression of CHOP/GADD153. The activity of the promoters of the ER chaperones is increased in UDP-Glc-deficient cells, but the activity of the CHOP/GADD153 promoter is not affected, in comparison with their respective activities in cells having compensated for the UDP-Glc deficiency. The results demonstrate that the unfolded protein response remains functionally intact in cells with a 65% decrease in the cellular UDP-Glc level and provide evidence that this decrease is a stress signal in mammalian cells, which triggers the coordinate overexpression of mitochondrial and ER chaperones, independently of the ER stress elements.

Enhanced expression of mRNAs of antisecretory factor-1, gp96, DAD1 and CDC34 in human hepatocellular carcinomas

To identify differentially expressed genes in hepatocarcinogenesis, we performed differential display analysis using surgically resected hepatocellular carcinoma (HCC) and adjacent non-tumorous liver tissues. We identified four cDNA fragments upregulated in HCC samples, encoding antisecretory factor-1 (AF), gp96, DAD1 and CDC34. Northern blot analysis demonstrated that these mRNAs were expressed preferentially in HCCs compared with adjacent non-tumorous liver tissues or normal liver tissues from non-HCC patients. The expression of these mRNAs was increased along with the histological grading of HCC tissues. These mRNA levels were also high in three human HCC cell lines (HuH-7, HepG2 and HLF), irrespective of the growth state. We also demonstrate that sodium butyrate, an inducer of differentiation, downregulated the expression of AF and gp96 mRNAs, supporting in part our pathological observation. Immunohistochemical analysis revealed that gp96 and CDC34 proteins were preferentially accumulated in cytoplasm and nuclei of HCC cells, respectively. Overexpression of these genes could be an important manifestation of HCC phenotypes and should provide clues to understand the molecular basis of hepatocellular carcinogenesis.

Expression of stress protein gp96, a tumor rejection antigen, in human colorectal cancer

Preparations of stress protein gp96 from tumor cells are active as tumor vaccines by eliciting immune responses against mixtures of individual tumor peptide antigens which are complexed to gp96. Due to the individual antigenicity of tumors, a vaccine consisting of tumor-derived gp96 has to be prepared individually for each patient from autologous tumor tissue. So far, gp96 expression by human tumors has not been analyzed. Here, we report stable and mostly homogenous expression of gp96 by colorectal cancer, which was enhanced compared to surrounding tumor stroma in 70% to 80% of colorectal cancer specimens. Fewer non-metastatic than metastatic primary cancer specimens showed enhanced gp96 expression. Glucose deprivation increased gp96 protein and RNA expression in the human colon cancer cell line HT-29 in accordance with the role of gp96 as a glucose-regulated stress protein. Additionally, TNF-alpha, interferons and other cytokines induced an increase of gp96 RNA expression in HT-29 cells, suggesting that gp96 expression by colorectal cancer cells can be influenced by different methods of immunomodulation. The stable and homogenous expression of gp96 in 19 primary and metastatic colorectal cancer specimens and the up-regulation of gp96 in colon cancer cells by glucose deprivation point to an essential role of this stress protein in colorectal cancer, presumably by protecting against hostile conditions of the tumor micro-environment like glucose deprivation. In view of these results, loss of gp96 expression by colorectal cancer cells as an immune escape mechanism is unlikely.

Stress protein/peptide complexes derived from autologous tumor tissue as tumor vaccines

Vaccination of inbred mice with tumor-derived stress proteins hsp70, hsp90, and gp96/grp94 elicits a protective immunity to the tumor from which the vaccine was purified. There is now comprehensive experimental evidence that the antigenicity of tumor-derived hsp70, hsp90, and gp96 preparations results from diverse arrays of endogenous peptide antigens complexed with these stress proteins. Vaccination with tumor-derived stress protein/peptide complexes leads to their uptake and processing by professional antigen-presenting cells and to presentation of associated tumor peptide antigens to cytotoxic T cells. This induces a tumor-specific cytotoxic T cell response. The attractiveness of the concept of using tumor-derived stress proteins as vaccines is derived from two observations: (i) tumor stress protein vaccines mirror the individual antigenicity of a tumor, which results from random mutations due to genetic instability; and (ii) stress proteins represent powerful adjuvants for the peptide antigens complexed to them.

Association of peptides with heat shock protein gp96 occurs in vivo and not after cell lysis

Immunization of mice and rats with gp96 preparations isolated from syngeneic cancers has been shown to elicit protective immunity to a number of cancers. The specific immunogenicity of gp96 preparations derives from the antigenic peptides chaperoned by the gp96 molecule and not from gp96 molecules per se. Studies reported here demonstrate that the association of peptides with gp96 occurs in vivo and is not a procedural artifact which occurs in vitro after cell lysis. This demonstration has a bearing on the proposed functional role of HSP peptide association in antigen processing and presentation by MHC I molecules.

Activation of the grp78 and grp94 promoters by hepatitis C virus E2 envelope protein

The hepatitis C virus E1 and E2 envelope proteins are targeted to the endoplasmic reticulum, but instead of being secreted, they are retained in a pre-Golgi compartment, at least partly in a misfolded state. Since secretory proteins which are retained in the endoplasmic reticulum frequently can activate the transcription of intraluminal chaperone proteins, we measured the effect of the E1 and E2 proteins on the promoters of two such chaperones, GRP78 (BiP) and GRP94. We found that E2 but not E1 protein activates these two promoters, as assayed by a reporter gene system. Furthermore, E2 but not E1 protein induces the synthesis of GRP78 from the endogenous cellular gene. We also found that E2 but not E1 protein expressed in mammalian cells is bound tightly to GRP78. This association may explain the ability of E2 protein to activate transcription, since GRP78 has been postulated to be a sensor of stress in the endoplasmic reticulum. Since overexpression of GRP78 has been shown to decrease the sensitivity of cells to killing by cytotoxic T lymphocytes and to increase tumorigenicity and resistance to antitumor drugs, this activity of E2 protein may be involved in the pathogenesis of hepatitis C virus-induced diseases.

Retroviral insertions in Evi12, a novel common virus integration site upstream of Tra1/Grp94, frequently coincide with insertions in the gene encoding the peripheral cannabinoid receptor Cnr2

The common virus integration site (VIS) Evi11 was recently identified within the gene encoding the hematopoietic G-protein-coupled peripheral cannabinoid receptor Cnr2 (also referred to as Cb2). Here we show that Cnr2 is a frequent target (12%) for insertion of Cas-Br-M murine leukemia virus (MuLV) in primary tumors in NIH/Swiss mice. Multiple provirus insertions in Evi11 were cloned and shown to be located within the 3' untranslated region of the candidate proto-oncogene Cnr2. These results suggest that proviral insertion in the Cnr2 gene is an important step in Cas-Br-M MuLV-induced leukemogenesis in NIH/Swiss mice. To isolate Evi11/Cnr2 collaborating proto-oncogenes, we searched for novel common VISs in the Cas-Br-M MuLV-induced primary tumors and identified a novel frequent common VIS, Evi12 (14%). Interestingly, 54% of the Evi11/Cnr2-rearranged primary tumors contained insertions in Evi12 as well, which suggests cooperative action of the target genes in these two common VISs in leukemogenesis. By interspecific backcross analysis it was shown that Evi12 resides on mouse chromosome 10 in a region that shares homology with human chromosomes 12q and 19p. Sequence analysis demonstrated that Evi12 is located upstream of the gene encoding the molecular chaperone Tra1/Grp94, which was previously mapped to mouse chromosome 10 and human chromosome 12q22-24. Thus, Tra1/Grp94 is a candidate target gene for retroviral activation or inactivation in Evi12. However, Northern and Western blot analyses did not provide evidence that proviral insertion had altered the expression of Tra1/Grp94. Additional studies are required to determine whether Tra1/Grp94 or another candidate proto-oncogene in Evi12 is involved in leukemogenesis.

De-regulation of GRP stress protein expression in human breast cancer cell lines

The stress-inducible glucose regulated proteins (GRPs), a class of calcium-binding molecular chaperones localized in the endoplasmic reticulum, have been implicated in the development of tumorigenicity, drug resistance, and cytotoxic immunology. This study investigates the expression pattern of GRP94 and GRP78 in a panel of breast carcinoma cell lines, as compared to two independently derived normal human breast epithelial cell lines. Here we report that a 3- to 5-fold increase in the basal level of the GRP94 protein was observed in all five breast carcinoma cell lines examined. The increase was independent of either the p53 or estrogen receptor status of the breast carcinomas. In carcinoma cells deprived of glucose, mimicking the conditions in poorly vascularized solid tumors, up to 9-fold induction of GRP94 was observed relative to the basal level expressed in a normal breast epithelial cell line. Interestingly, while the majority of the breast cancer cell lines can respond to tunicamycin- and thapsigargin-induced stress by increasing the steady state levels of grp94 and grp78 transcripts, the induction at the GRP protein level is variable and does not always correspond with the transcript level. Further, we discovered that one of the human breast carcinoma cell lines, MCF-7, has specifically lost its ability to respond to tunicamycin stress.

The 90-kDa molecular chaperone family: structure, function, and clinical applications. A comprehensive review

The 90-kDa molecular chaperone family (which comprises, among other proteins, the 90-kDa heat-shock protein, hsp90 and the 94-kDa glucose-regulated protein, grp94, major molecular chaperones of the cytosol and of the endoplasmic reticulum, respectively) has become an increasingly active subject of research in the past couple of years. These ubiquitous, well-conserved proteins account for 1-2% of all cellular proteins in most cells. However, their precise function is still far from being elucidated. Their involvement in the aetiology of several autoimmune diseases, in various infections, in recognition of malignant cells, and in antigen-presentation already demonstrates the essential role they likely will play in clinical practice of the next decade. The present review summarizes our current knowledge about the cellular functions, expression, and clinical implications of the 90-kDa molecular chaperone family and some approaches for future research.

Mechanism for the suppression of the mammalian stress response by genistein, an anticancer phytoestrogen from soy

BACKGROUND

Soy products contain high levels of genistein, a phytoestrogen that is a potent inhibitor of cell proliferation and angiogenesis. Genistein has been found to inhibit the growth of carcinogen-induced cancers in rats and human leukemia cells transplanted into mice. The induction of stress proteins (e.g., glucose-related proteins and heat shock proteins) in tumor cells has been shown to protect them against programmed cell death; this stress response is inhibited by genistein. The mechanism(s) by which genistein affects certain stress response genes was explored in this study.

METHODS

Mammalian cell cultures were treated with azetidine, a proline analog, which elicits a stress response that includes the induction of the expression of glucose-regulated protein GRP78 and heat shock protein HSP70. The effects of azetidine and/or genistein treatment on cellular levels of grp78 and hsp70 messenger RNAs and proteins were measured by northern blot hybridization and western blot analyses, respectively, and the binding of nuclear factors to sequence motifs in the upstream (promoter) regions of these two genes were examined by electrophoretic mobility shift assays.

RESULTS

Genistein antagonized the binding of a specific transcription factor, nuclear factor-Y/CCAAT binding factor (NF-Y/CBF), to the CCAAT sequence element most proximal to the transcription start sites in the hsp70 and grp78 promoters; this CCAAT element was previously shown to be necessary for full-stress inducibility of both genes. Treatment of cells with genistein converted NF-Y/CBF into a nonbinding, transcriptionally inactive form.

IMPLICATION

The anticancer effects of genistein may be related to its ability to reduce the expression of stress response-related genes.

Molecular chaperones in the etiology and therapy of cancer

Molecular chaperones are ubiquitous, well-conserved proteins that account for 2-5 % of all cellular proteins in most cells. The present review summarizes our current knowledge about their involvement in the etiology and therapy of cancer with special emphasis on the expression of chaperones in malignant cells, their role in folding of (proto)oncogene products, cell cycle regulation, cell differentiation and apoptosis, development of metastasis, and their participation in the recognition of malignant cells. We also overview the importance of chaperones in hyperthermia, drug resistance, and recent approaches in chaperone-immunotherapy.

Degenerative changes in spermatogonia are associated with loss of glucose transporter (Glut 3) in abdominal testis of surgically induced unilateral cryptorchidism in rats

Expression of facilitative glucose transporters (Glut 1, 2 and 3) was examined by Western blot analyses 10, 20 and 30 days following surgically induced unilateral abdominal cryptorchidism. The cryptorchid testes exhibited marked degenerative changes in the seminiferous tubules and spermatogonia, impaired and incomplete spermatogenesis and lack of spermatozoa in the lumen. Immunoblotting of testis proteins with Glut transporter antibodies revealed only the presence of Glut 2 and 3 proteins. Glut 2 expression in abdominal testis was increased (45%, 67%, and 40% at 10, 20 and 30 days, respectively) but no significant change was observed in contralateral scrotal testis. Glut 3 expression was reduced by 85-95% compared with contralateral scrotal testis. A significant decrease in Glut 3 levels in abdominal testis was accompanied by an increase in scrotal testis Glut 3 content (80%, 144% and 212% at 10, 20 and 30 days, respectively) compared to age matched control rats. These results suggested that the degenerative changes in abdominal testis may be associated with decreased Glut 3 mediated glucose transport in seminiferous tubules and spermatogonia.

Study of immune response to tumors in the rat

Use of the rat as host for the study of cancer has become popular for several reasons. The larger body size compared to mice is especially convenient for lines of experiments involving surgical manipulation, transplantation, or biochemical purification of molecules of interest. Immune response to cancer is also studied in rat models, and this article focuses on the methodological aspects of in vivo and in vitro protocols related to rat tumor immunology.

Interleukin-6 upregulates GP96 expression in breast cancer

Interleukin-6 is associated with poor prognosis in breast cancer. Expression of GP96, a glucose regulated stress protein, is related to drug resistance in tumor cells. Interleukin-6 has previously been shown to induce GP96 expression in a murine myeloblastic cell line. BT474 or MDA-MB231 cells were incubated with recombinant Interleukin-6 (100 to 750 U/ml) for 24 hr. To establish a time course for GP96 induction, MDA-MB231 cells were incubated with 250 U/ml recombinant interleukin-6 for 0-48 hr. Following incubation, cells were washed twice in phosphate-buffered saline (PBS) and cell lysates were prepared by adding 100 microliters of PBS and freezing at -20 degrees C. GP96 was assessed by immunoblotting. Breast tumor tissue and histologically normal breast tissue were obtained within 1 hr of resection and flash frozen in liquid nitrogen. Tissue was homogenized in ice-cold PBS and cell debris was pelleted by centrifugation at 300g at 4 degrees C for 5 min. Supernatants were collected and assayed for interleukin-6 by ELISA, and GP96 by immunoblotting. Both interleukin-6 (P < 0.001) and GP96 are elevated in breast tumor tissue compared to histologically normal tissue. Interleukin-6 (> or = 250 U/ml for > or = 12 hr) induces GP96 in the metastatic breast cancer cell line, MDA-MB231, but has no effect on GP96 levels in the primary cell line, BT474. Elevated interleukin-6 in breast tumors may induce GP96 expression in tumor cells conferring a survival advantage by rendering them resistant to cytotoxic therapy and other forms of stress.

Endoplasmic reticulum stress-inducible protein GRP94 is associated with an Mg2+-dependent serine kinase activity modulated by Ca2+ and GRP78/BiP

The 94-kDa glucose-regulated protein (GRP94) is a glycoprotein in the endoplasmic reticulum (ER). It has been characterized as a Ca2+-binding protein and a molecular chaperone. In this report we show that highly purified GRP94 exhibits an active Mg2+-dependent serine kinase activity (termed 94-kinase). The 94-kinase can be recovered from ER membrane fractions and is able to phosphorylate both the constitutive and stress-induced forms of GRP94, correlating with their induction kinetics. The 94-kinase activity is distinct from casein kinase II. In contrast to the heat-stable, Ca2+-dependent autophosphorylation activity recently reported for GRP94, the labile 94-kinase activity is inhibited by Ca2+. We determined that the phosphopeptide map of in vitro phosphorylated GRP94 by the 94-kinase resembles that of the in vivo phosphorylated GRP94. Further, the 94-kinase activity can be specifically stimulated by GRP78, a coregulated protein in the ER known to interact with GRP94.