Photoimmunotherapy of hepatocellular carcinoma-targeting Glypican-3 combined with nanosized albumin-bound paclitaxel

AIM

Effectiveness of Glypican-3 (GPC3)-targeted photoimmunotherapy (PIT) combined with the nanoparticle albumin-bound paclitaxel (nab-paclitaxel) for hepatocellular carcinoma was evaluated.

MATERIALS & METHODS

GPC3 expressing A431/G1 cells were incubated with a phthalocyanine-derivative, IRDye700DX (IR700), conjugated to an anti-GPC3 antibody, IR700-YP7 and exposed to near-infrared light. Therapeutic experiments combining GPC3-targeted PIT with nab-paclitaxel were performed in A431/G1 tumor-bearing mice.

RESULTS

IR700-YP7 bound to A431/G1 cells and induced rapid target-specific necrotic cell death by near-infrared light exposure in vitro. IR700-YP7 accumulated in A431/G1 tumors. Tumor growth was inhibited by PIT compared with nontreated control. Additionally, PIT dramatically increased nab-paclitaxel delivery and enhanced the therapeutic effect.

CONCLUSION

PIT targeting GPC3 combined with nab-paclitaxel is a promising method for treating hepatocellular carcinoma.

New high affinity monoclonal antibodies recognize non-overlapping epitopes on mesothelin for monitoring and treating mesothelioma

Mesothelin is an emerging cell surface target in mesothelioma and other solid tumors. Most antibody drug candidates recognize highly immunogenic Region I (296–390) on mesothelin. Here, we report a group of high-affinity non-Region I rabbit monoclonal antibodies. These antibodies do not compete for mesothelin binding with the immunotoxin SS1P that binds Region I of mesothelin. One pair of antibodies (YP218 and YP223) is suitable to detect soluble mesothelin in a sandwich ELISA with high sensitivity. The new assay can also be used to measure serum mesothelin concentration in mesothelioma patients, indicating its potential use for monitoring patients treated with current antibody therapies targeting Region I. The antibodies are highly specific and sensitive in immunostaining of mesothelioma. To explore their use in tumor therapy, we have generated the immunotoxins based on the Fv of these antibodies. One immunotoxin (YP218 Fv-PE38) exhibits potent anti-tumor cytotoxicity towards primary mesothelioma cell lines in vitro and an NCI-H226 xenograft tumor in mice. Furthermore, we have engineered a humanized YP218 Fv that retains full binding affinity for mesothelin-expressing cancer cells. In conclusion, with their unique binding properties, these antibodies may be promising candidates for monitoring and treating mesothelioma and other mesothelin-expressing cancers.

Glypican-3 targeted human heavy chain antibody as a drug carrier for hepatocellular carcinoma therapy

Glypican-3 (GPC3) represents an attractive target for hepatocellular carcinoma (HCC) therapy because it is highly expressed in HCC but not in adult normal tissue. Recently, high affinity anti-GPC3 antibodies have been developed; however, full antibodies may not penetrate evenly into tumor parenchyma, reducing their effectiveness. In this study, we compared a whole IgG antibody, anti-GPC3 YP7, with an anti-GPC3 human heavy chain antibody, HN3, with regard to their relative therapeutic effects. Both YP7 and HN3 bound to GPC3-positive A431/G1 cells and were internalized by the cells by in vitro evaluation with (125)I- and (111)In-radiolabeling antibodies. In vivo biodistribution and tumor accumulation was performed with (111)In-labeled antibodies, and intratumoral microdistribution was evaluated using fluorescently labeled antibodies (IR700). HN3 showed similar high tumor accumulation but superior homogeneity within the tumor compared with YP7. Using the same IR700 conjugated antibodies photoimmunotherapy (PIT) was performed in vitro and in a tumor-bearing mouse model in vivo. PIT with IR700-HN3 and IR700-YP7 demonstrated that comparable results could be achieved despite of low reaccumulation 24 h after the first NIR light exposure. These results indicated that a heavy-chain antibody, HN3, showed more favorable characteristics than YP7, a conventional IgG, as a therapeutic antibody platform for designing molecularly targeted agents against HCC.

Cytomegalovirus and Epstein-Barr virus in breast cancer

Findings of polymerase chain reaction (PCR) studies of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) and breast cancer vary, making it difficult to determine whether either, both, or neither virus is causally associated with breast cancer. We investigated CMV and EBV in paired samples of breast cancer and normal breast tissue from 70 women using quantitative PCR. A serum sample from each woman was tested for CMV and EBV IgG. To place our results in context, we reviewed the existing literature and performed a meta-analysis of our results together with previous PCR studies of EBV, CMV, and breast cancer. Of the serology samples, 67 of 70 (96%) were EBV IgG positive and 49 of 70 (70%) were CMV IgG positive. QPCR detected EBV in 24 (34%) of the tumour and 9 (13%) of the paired normal specimens and CMV in 0 (0%) of the tumour and 2 (3%) of the paired normal specimens. Our findings, together with earlier results summarised in the meta-analysis, suggest several possibilities: variable findings may be due to limitations of molecular analyses; 'hit and run' oncogenesis may lead to inconsistent results; one or both viruses has a role at a later stage in breast cancer development; infection with multiple viruses increases breast cancer risk; or neither virus has a role. Future studies should focus on ways to investigate these possibilities, and should include comparisons of breast cancer tissue samples with appropriate normal tissue samples.

Identification of one-electron reductases that activate both the hypoxia prodrug SN30000 and diagnostic probe EF5

SN30000 is a second-generation benzotriazine-N-oxide hypoxia-activated prodrug scheduled for clinical trial. Previously we showed that covalent binding of the hypoxia probe EF5 predicts metabolic activation of SN30000 in a panel of cancer cell lines under anoxia, suggesting that they are activated by the same reductases. However the identity of these reductases is unknown. Here, we test whether forced expression of nine oxidoreductases with known or suspected roles in bioreductive prodrug metabolism (AKR1C3, CYB5R3, FDXR, MTRR, NDOR1, NOS2A, NQO1, NQO2 and POR) enhances oxic or anoxic reduction of SN30000 and EF5 by HCT116 cells. Covalent binding of (14)C-EF5 and reduction of SN30000 to its 1-oxide and nor-oxide metabolites was highly selective for anoxia in all lines, with significantly elevated anoxic metabolism of both compounds in lines over-expressing POR, MTRR, NOS2A or NDOR1. There was a strong correlation between EF5 binding and SN30000 metabolism under anoxia across the cell lines (R(2)=0.84, p=0.0001). Antiproliferative potency of SN30000 under anoxia was increased most strongly by overexpression of MTRR and POR. Transcript abundance in human tumours, evaluated using public domain mRNA expression data, was highest for MTRR, followed by POR, NOS2A and NDOR1, with little variation between tumour types. Immunostaining of tissue microarrays demonstrated variable MTRR protein expression across 517 human cancers with most displaying low expression. In conclusion, we have identified four diflavin reductases (POR, MTRR, NOS2A and NDOR1) capable of reducing both SN30000 and EF5, further supporting use of 2-nitroimidazole probes to predict the ability of hypoxic cells to activate SN30000.

Inactivation of Wnt signaling by a human antibody that recognizes the heparan sulfate chains of glypican-3 for liver cancer therapy

Wnt signaling is important for cancer pathogenesis and is often up-regulated in hepatocellular carcinoma (HCC). Heparan sulfate proteoglycans (HSPGs) function as coreceptors or modulators of Wnt activation. Glypican-3 (GPC3) is an HSPG that is highly expressed in HCC, where it can attract Wnt proteins to the cell surface and promote cell proliferation. Thus, GPC3 has emerged as a candidate therapeutic target in liver cancer. While monoclonal antibodies to GPC3 are currently being evaluated in preclinical and clinical studies, none have shown an effect on Wnt signaling. Here, we first document the expression of Wnt3a, multiple Wnt receptors, and GPC3 in several HCC cell lines, and demonstrate that GPC3 enhanced the activity of Wnt3a/β-catenin signaling in these cells. Then we report the identification of HS20, a human monoclonal antibody against GPC3, which preferentially recognized the heparan sulfate chains of GPC3, both the sulfated and nonsulfated portions. HS20 disrupted the interaction of Wnt3a and GPC3 and blocked Wnt3a/β-catenin signaling. Moreover, HS20 inhibited Wnt3a-dependent cell proliferation in vitro and HCC xenograft growth in nude mice. In addition, HS20 had no detectable undesired toxicity in mice. Taken together, our results show that a monoclonal antibody primarily targeting the heparin sulfate chains of GPC3 inhibited Wnt/β-catenin signaling in HCC cells and had potent antitumor activity in vivo.

CONCLUSION

An antibody directed against the heparan sulfate of a proteoglycan shows efficacy in blocking Wnt signaling and HCC growth, suggesting a novel strategy for liver cancer therapy.

A human single-domain antibody elicits potent antitumor activity by targeting an epitope in mesothelin close to the cancer cell surface

Monoclonal antibodies against mesothelin are being evaluated for the treatment of mesothelioma and multiple forms of cancers, and show great promise for clinical development for solid cancers. Antibodies against mesothelin have been shown to act via immunotoxin-based inhibition of tumor growth and induction of antibody-dependent cell-mediated cytotoxicity (ADCC). However, complement-dependent cytotoxicity (CDC), considered an important additional mechanism of therapeutic antibodies against tumors, is inactive for such antibodies. Here, we used phage display antibody engineering technology and synthetic peptide screening to identify SD1, a human single-domain antibody to mesothelin. SD1 recognizes a conformational epitope at the C-terminal end (residues 539-588) of mesothelin close to the cell surface. To investigate SD1 as a potential therapeutic agent, we generated a recombinant human Fc (SD1-hFc) fusion protein. Interestingly, the SD1-hFc protein exhibits strong CDC activity, in addition to ADCC, against mesothelin-expressing tumor cells. Furthermore, it causes growth inhibition of human tumor xenografts in nude mice as a single agent. SD1 is the first human single-domain antibody targeting mesothelin-expressing tumors, shows potential as a cancer therapeutic candidate, and may improve current antibody therapy targeting mesothelin-expressing tumors.

High-affinity monoclonal antibodies to cell surface tumor antigen glypican-3 generated through a combination of peptide immunization and flow cytometry screening

Isolating high-affinity antibodies against native tumor antigens on the cell surface is not straightforward using standard hybridoma procedures. Here, we describe a combination method of synthetic peptide immunization and high-throughput flow cytometry screening to efficiently isolate hybridomas for cell binding. Using this method, we identified high-affinity monoclonal antibodies specific for the native form of glypcian-3 (GPC3), a target heterogeneously expressed in hepatocellular carcinoma (HCC) and other cancers. We isolated a panel of monoclonal antibodies (YP6, YP7, YP8, YP9 and YP9.1) for cell surface binding. The antibodies were used to characterize GPC3 protein expression in human liver cancer cell lines and tissues by flow cytometry, immunoblotting and immunohistochemistry. The best antibody (YP7) bound cell surface-associated GPC3 with equilibrium dissociation constant, KD = 0.3 nmol/L and was highly specific for HCC, not normal tissues or other forms of primary liver cancers (such as cholangiocarcinoma). Interestingly, the new antibody was highly sensitive in that it detected GPC3 in low expression ovarian clear cell carcinoma and melanoma cells. The YP7 antibody exhibited significant HCC xenograft tumor growth inhibition in nude mice. These results describe an improved method for producing high-affinity monoclonal antibodies to cell surface tumor antigens and represent a general approach to isolate therapeutic antibodies against cancer. The new high-affinity antibodies described here have significant potential for GPC3-expressing cancer diagnostics and therapy.

Guideline-based treatment utilization, treatment time, and cost of chemotherapy for metastatic colon cancer patients treated in U.S. community oncology practices from 2005 to 2009

e14118

Background: Adherence (Ad) to national treatment guidelines (TG) is important in improving the quality, outcomes, and cost of cancer treatment (TX) in the U.S. We examined regimens (Reg) utilized, TG-Ad, time on metastatic TX, and cost of chemotherapy prescribed by U.S. community oncology practices to treat patients (Pts) with metastatic colon cancer (MCC) in 2005 and 2009. Methods: Adult colon cancer Pts beginning first line metastatic treatment (LOT-1) in each full calendar year for 2005 and 2009 were reviewed from a large U.S. medical oncology clinical database derived from web-based drug dispensing technology. Reg utilized and 2-yr time on metastatic TX were analyzed and compared to TG recommendations. Reg costs based on Medicare reimbursement were compared. Results: The average number of LOT and number of unique drugs Pts were exposed to were similar between 2005 and 2009. About 70% of Pts received only one LOT. In LOT-1 and 2, TG regs were prescribed more often than Non-TG regs for both groups. TG-Ad was significantly higher in 2009 than in 2005 for LOT-1 (p < 0.0001). Pts receiving TG-Ad Reg for LOT-1 had a significantly longer total metastatic treatment time in both 2005 and 2009. In both 2005 and 2009, FOLFOX+Bev was the most frequent LOT-1 Reg given (37% of Pts), while FOLFIRI+Bev was the most frequent LOT-2 Reg given. 69% of Pts received Bev with LOT-1 in both 2005 and 2009; of those, 28-30% continued to receive Bev with LOT-2. Costs for the top 5 LOT-1 Regs were $17,031 to $34,400 and $5,512 to $39,835 for 2005 and 2009, respectively. Conclusions: U.S. community oncology practices significantly improved guideline Ad in the TX of MCC from 2005 to 2009. In LOT-1, TG Regs were prescribed more than non-TG Regs for both groups. TG Ad for LOT-1 significantly improved time on metastatic TX in both groups. FOLFOX+Bev and FOLFIRI+Bev were most frequently prescribed for LOT-1 and LOT-2, respectively. Costs for the five most utilized Regs vary considerably. [Table: see text]

The development and characterization of a human mesothelioma in vitro 3D model to investigate immunotoxin therapy

Background

Tumor microenvironments present significant barriers to penetration by antibodies and immunoconjugates. Tumor microenvironments, however, are difficult to study in vitro. Cells cultured as monolayers exhibit less resistance to therapy than those grown in vivo and an alternative research model more representative of the in vivo tumor is more desirable. SS1P is an immunotoxin composed of the Fv portion of a mesothelin-specific antibody fused to a bacterial toxin that is presently undergoing clinical trials in mesothelioma.

Methodology/Principal Findings

Here, we examined how the tumor microenvironment affects the penetration and killing activity of SS1P in a new three-dimensional (3D) spheroid model cultured in vitro using the human mesothelioma cell line (NCI-H226) and two primary cell lines isolated from the ascites of malignant mesothelioma patients. Mesothelioma cells grown as monolayers or as spheroids expressed comparable levels of mesothelin; however, spheroids were at least 100 times less affected by SS1P. To understand this disparity in cytotoxicity, we made fluorescence-labeled SS1P molecules and used confocal microscopy to examine the time course of SS1P penetration within spheroids. The penetration was limited after 4 hours. Interestingly, we found a significant increase in the number of tight junctions in the core area of spheroids by electron microscopy. Expression of E-Cadherin, a protein involved in the assembly and sealing of tight junctions and highly expressed in malignant mesothelioma, was found significantly increased in spheroids as compared to monolayers. Moreover, we found that siRNA silencing and antibody inhibition targeting E-Cadherin could enhance SS1P immunotoxin therapy in vitro.

Conclusion/Significance

This work is one of the first to investigate immunotoxins in 3D tumor spheroids in vitro. This initial description of an in vitro tumor model may offer a simple and more representative model of in vivo tumors and will allow for further investigations of the microenvironmental effects on drug penetration and tumor cell killing. We believe that the methods developed here may apply to the studies of other tumor-targeting antibodies and immunoconjugates in vitro.

Mesothelin as a potential therapeutic target in human cholangiocarcinoma

Background: Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the two most common primary liver cancers, yet there have been no significant advances in effective therapeutics. Mesothelin has been reported as a new therapeutic target in various types of cancer. Here, we investigated the expression of mesothelin in liver cancer and its potential role as a novel therapeutic target for immunotherapy.

Methods: HCC and CCA specimens were examined by immunohistochemistry for mesothelin expression. Protein expression was assessed by immunoblotting and flow cytometry. The SS1P immunotoxin targeting mesothelin was evaluated in the well-established CCA cell lines HuCCT1, HuH-28, KMBC, KMCH, Mz-ChA-1 and OZ.

Results: We showed strong immunochemical mesothelin staining in 33% of the surgically resected CCA specimens and 3 of 6 CCA cell lines (OZ, KMBC and KMCH). No mesothelin staining was found in HCC or normal liver tissue. Mesothelin was primarily localized to the cellular plasma membrane and the mature form (molecular weight, ~40 kDa) was expressed at a high level in CCA tissues. Moreover, 22% of CCA specimens had a high mesothelin expression level which was comparable to the CCA cell line models. Interestingly, SS1P showed very high and specific growth inhibition when added to mesothelin-expressing CCA cells with IC₅₀ values ranging from 0.5 to 11 ng/mL.

Conclusions: Mesothelin is overexpressed in one-third of CCA tissues. SS1P targeting mesothelin reveals a remarkable single agent activity against CCA in vitro. These findings indicate a potential for SS1P in the immunotherapeutic treatment of CCA.

Abstract 648: A 3D spheroid model of human mesothelioma to investigate antibody therapeutics

The formation of tumor cells traditionally cultured in vitro as monolayers frequently exhibit less drug resistance than tumors in vivo and are inadequate models for screening anti-cancer agents. Mesothelioma, a highly fatal asbestos-induced cancer of the mesothelium, is notoriously resistant to traditional chemotherapy and radiation. In this study, the development of multicellular and apoptotic resistance in human mesothelioma cell lines is examined using a 3D spheroid model cultured in vitro, which more closely depicts in vivo tumor resistance. We hypothesized that poor drug penetration of spheroid tumors is associated with the number of cellular contacts related to its 3D shape. In addition, we asked whether its resistance to cell death was directly related to the Bcl-2-regulated mitochondrial pathway. To test this, we cultured tumors cells both as monolayers and spheroids and measured the concentration of a fluorescently-labeled immunotoxin, SS1P, as a percentage of live cells. Antigen expression was determined via flow cytometry, and tumors were visualized using transmission and scanning electron microscopy, where a higher number of tight junctions were found in the core area of the spheroid. Additionally, we analyzed the expression of several proteins related to apoptosis in cell lysates for both monolayers and spheroids by western blotting. We found that some human mesothelioma cells form spheroids within 24 hours in the absence of Matrigel. The expression levels of mesothelin and CA125 - two established tumor antigens - are comparable between mesothelioma cells obtained from monolayer and spheroid; however, the cytotoxicity assay (IC50) of the anti-mesothelin immunotoxin SS1P shows that it is at least 100 times less active for spheroids than for monolayers. SS1P also shows incomplete penetration in spheroids, with limited penetration after 4 to 8 hours. Regarding cellular contacts, E-Cadherin is expressed in both monolayers and spheroids, but is significantly increased in spheroids. However, no bands are seen for prosurvival protein Bcl-2, and no difference in expression is found for prosurvival protein MCL-1. As for pro-apoptotic molecules, Bax and Bak, Bax did not show any changes, whereas Bak appeared only in monolayer and was absent for spheroid. Our results indicate that the upregulation of E-Cadherin expression in spheroids may be related to the increased number of tight junctions, thereby inhibiting the penetration of immunotoxins. Likewise, downregulation of the pro-apoptotic molecule Bak may cause resistance to immunotoxin-induced mitochondria-dependent apoptosis in spheroids. We conclude that using a biologically relevant 3D spheroid model more closely resembles similar types of resistance to that of in vivo tumors. We believe that it is a useful in vitro tumor model that will provide greater opportunity for investigating and screening antibody therapeutics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 648.

Blunted hepcidin response to oral iron challenge in HFE-related hemochromatosis

Inadequate hepcidin synthesis leads to iron overload in HFE-related hemochromatosis. We explored the regulation of hepcidin by iron in 88 hemochromatosis patients (61 C282Y/C282Y, 27 C282Y/H63D) and 23 healthy controls by analyzing urinary hepcidin before and 24 hours after a 65-mg oral iron dose. Thirty-four patients were studied at diagnosis and had iron overload, and 54 patients were iron depleted. At diagnosis, hepcidin values in C282Y homozygotes were similar to controls, whereas values in C282Y/H63D heterozygotes were higher (P = .02). However, the hepcidin/ferritin ratio was decreased in both homozygotes (P < .001) and heterozygotes (P = .017), confirming the inadequate hepcidin production for the iron load with both genotypes. In iron-depleted patients of both genotypes studied at a time remote from phlebotomy, basal hepcidin was still lower than in controls (P < .001 for C282Y/C282Y and P = .002 for heterozygotes). After an iron challenge, mean urinary hepcidin excretion increased in controls (P = .001) but not patients, irrespective of genotype and iron status. Significant hepcidin increase ( ≥ 10 ng/mg creatinine) was observed in 74% of controls, 15% of homozygotes, and 32% of heterozygotes. The hepcidin response to oral iron is blunted in HFE-related hemochromatosis and not improved after iron depletion. The findings support the involvement of HFE in iron sensing and subsequent regulation of hepcidin.

Viral evolution of hepatitis C in injection drug users

Injection drug users represent the largest cohort of patients with established hepatitis C virus (HCV) infection as well as the group that is at highest risk for new infections. Most published studies have focused on the clinical consequences of established HCV infection and have not examined the consequences of new infection. The aim of the current study was to measure the virological consequences of HCV in patients with ongoing injection drug use that might pose a risk for new and/or for superinfection with additional strains of HCV. We examined the following groups: (a) those with resolved HCV infection with ongoing injection drug use, (b) those with chronic infection who continued to inject and (c) those with chronic infection who no longer injected. Our study demonstrated a spectrum of responses. The majority of patients appeared to be 'protected' from new infection. None of six patients with resolved infection had detectable HCV RNA by quantitative or qualitative PCR when followed for 1 year. Similarly, despite ongoing injection drug use, no patient with persistent infection had a 'switch' in HCV genotype indicative of possible superinfection. Virological analysis of HCV quasispecies to detect possible infection with new variants of HCV in patients with apparently 'stable' infection, indicated divergence of virus over time, divergence that was unrelated to injection drug behaviour. Thus, patients with ongoing or prior HCV infection appear to develop immunity that protects against further infection with HCV despite repeated exposure.

Evolution of hepatitis C virus quasispecies in patients with severe cholestatic hepatitis after liver transplantation

Evolution of hepatitis C quasispecies may be one mechanism by which fibrosing cholestatic hepatitis develops after liver transplantation. In this study, we compared changes in quasispecies complexity and/or divergence in (1) hepatitis C-infected immunosuppressed transplant recipients and in immunocompetent controls; (2) transplant recipients with mild recurrence, and in those with the most severe form of posttransplantation recurrence. Quasispecies were measured in 12 hepatitis C-infected patients pretransplantation and posttransplantation (6 with mild and 6 with severe recurrence), and in 5 immunocompetent patients with similar follow-up, and characterized by heteroduplex mobility and sequence analysis of the hypervariable region. Although the number of variants (complexity) did not change with time in either group, there was a qualitative change in the variants with time (divergence) in immunocompromised, but not in immunocompetent patients. These changes were most marked with severe recurrence, and preceded the development of severe disease. Phylogenetic analysis confirmed that most posttransplantation variants were unrelated to those detected pretransplantation. These observations suggest that in the absence of immune suppression, there is minor evolution of quasispecies. With immune suppression, divergence of quasispecies is enhanced, resulting in selection/emergence of many new variants, particularly in those with fibrosing cholestatic hepatitis. Thus, quasispecies may influence disease progression in immune suppressed populations.

Evolution of viral quasispecies in interferon-treated patients with chronic hepatitis C virus infection

BACKGROUND/AIMS

To evaluate whether interferon treatment failure/relapse is related to changes in hepatitis C virus quasispecies complexity (number of variants) or diversity (genetic relatedness of variants).

METHODS

We analyzed hypervariable region heterogeneity in hepatitis C virus-infected patients by heteroduplex mobility assay and by phylogenetic analysis of sequenced clones. Sera from 11 patients were tested. Response was defined biochemically and virologically. Patients were treated with 3 or 6 MIU interferon for 6 months and followed up for 6 months. Four patients were non-responders, four were transient responders and three untreated patients served as controls. Three time points were studied for the non-responders (pre-interferon, end of interferon, end of 6 months of follow-up), two for the transient responders (pre-interferon and post follow-up) and two for the controls (1 year apart). A total of 260 clones were examined by heteroduplex mobility assay and 144 clones were sequenced.

RESULTS

A linear correlation between heteroduplex mobility and nucleotide substitutions was observed, validating this method for assessment of quasispecies diversity. Although complexity at each time point was similar in all groups, diversity increased significantly with interferon treatment. The percentage of new variants in follow up was significantly higher in non-responders than in controls. These new variants exhibited a greater change in heteroduplex mobility, a higher percentage of changes in amino acids in non-responders compared to controls and were found to cluster separately from pretreatment variants when analyzed phylogenetically. These changes were less marked in transient responders.

CONCLUSIONS

These mutations may allow hepatitis C virus to escape antiviral effects of interferon therapy.

Feeding practices and dental caries in an urban Canadian population of Vietnamese preschool children

The aim of this project was to determine the severity of nursing caries, and to examine contributing behavioral factors, in a group of Vietnamese families in British Columbia, Canada. The data collected became the basis for a community-based oral health promotion program. Information on feeding, dental health practices, and dental caries were collected for 60 mother/child pairs. For children > or = 18 mos, prevalence of nursing caries was 64 percent. Sixty-five percent of all children had a naptime bottle, and 85 percent > or = 18 mos had a "comfort" bottle that was carried around, and drunk from during the day. Milk was the most common beverage. A "comfort" bottle was significantly related to the presence of nursing caries, P = 0.02; a naptime bottle had a less significant association, P = 0.07. Dental knowledge questions revealed that all mothers knew that a child who had a "comfort" bottle could get tooth decay, but 63 percent thought that cavities were not a problem in baby teeth.

Epithelial immaturity and multiorgan failure in mice lacking epidermal growth factor receptor

Since the discovery that epidermal growth factor (EGF) can accelerate opening of the eyelids, the EGF receptor (EGF-R) has been extensively studied and is now considered to be a prototype tyrosine kinase receptor. Binding of EGF or of transforming growth factor-alpha (TGF-alpha) or other related factors activates the receptor and induces cell proliferation and differentiation. Although it is not found on haematopoietic cells, the EGF-R is widely expressed in mammals and has been implicated in various stages of embryonic development. Here we investigate the developmental and physiological roles of this receptor and its ligands by inactivating the gene encoding EGF-R. We find that EGF-R-/- mice survive for up to 8 days after birth and suffer from impaired epithelial development in several organs, including skin, lung and gastrointestinal tract.