Reciprocal antagonism of PIN1-APC/CCDH1 governs mitotic protein stability and cell cycle entry

Induced oncoproteins degradation provides an attractive anti-cancer modality. Activation of anaphase-promoting complex (APC/CCDH1) prevents cell-cycle entry by targeting crucial mitotic proteins for degradation. Phosphorylation of its co-activator CDH1 modulates the E3 ligase activity, but little is known about its regulation after phosphorylation and how to effectively harness APC/CCDH1 activity to treat cancer. Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1)-catalyzed phosphorylation-dependent cis-trans prolyl isomerization drives tumor malignancy. However, the mechanisms controlling its protein turnover remain elusive. Through proteomic screens and structural characterizations, we identify a reciprocal antagonism of PIN1-APC/CCDH1 mediated by domain-oriented phosphorylation-dependent dual interactions as a fundamental mechanism governing mitotic protein stability and cell-cycle entry. Remarkably, combined PIN1 and cyclin-dependent protein kinases (CDKs) inhibition creates a positive feedback loop of PIN1 inhibition and APC/CCDH1 activation to irreversibly degrade PIN1 and other crucial mitotic proteins, which force permanent cell-cycle exit and trigger anti-tumor immunity, translating into synergistic efficacy against triple-negative breast cancer.

A Comparison of Clinicopathologic Outcomes and Patterns of Lymphatic Spread across Neoadjuvant Chemotherapy, Neoadjuvant Chemoradiotherapy and Neoadjuvant Immunochemotherapy in Locally Advanced Esophageal Squamous Cell Carcinoma

PURPOSE/OBJECTIVE(S)

To evaluate the differences in pathologic complete response (pCR) rates, TRG score, pathologic T stage and the pattern of lymphatic spread among patients receiving neoadjuvant chemotherapy (NCT) or neoadjuvant chemoradiotherapy (NCRT) or neoadjuvant immunochemotherapy (NICT) prior to esophagectomy for locally advanced esophageal squamous cell carcinoma (ESCC).

MATERIALS/METHODS

A total of 702 patients with ESCC who completed transthoracic esophagectomy followed neoadjuvant therapy at three cancer centers from January 2017 to December 2022 were enrolled. Among the included patients, 382 patients were treated with NCR, 172 with NCRT, and 148 with NICT. Inverse probability of treatment weighting (IPTW) was performed to control potential confounding factors. Pathological response of primary tumor was evaluated using the Chirieac modified tumor regression grade (TRG) system. The complete regression of primary lesion and nodal metastases were considered pCR. Lymph node classification system used the 8th edition of AJCC. Specimens were assessed for pattern of lymphatic spread.

RESULTS

After adjusting for baseline characteristics, the R0 resection rate did not significantly differ between the patients receiving NCT or NCRT or NICT (99.48% vs.100% vs.98.65%, P = 0.273). Compared with the NCT group, the NCRT group and NICT group had an advantage in pathological response (P<0.05). The pCR rate was 7.07% in the NCT group, 30.23% in the NCRT group, and 22.30% in the NICT group. Compared to the other two groups, the TRG score (P<0.05) and pathologic T stage (P<0.05) in the NCT group were significantly higher. In the NCT group, 9.97% had ypT0 disease, compared with 35.76% in the NCRT group and 25.68% in the NICT group. And in the NCT group, 9.71% had TRG1 disease, compared with 32.76% in the NCRT group and 25% in the NICT group. Compared with NICT, NCRT can significantly reduce the rate of LNM in station 1R (0 vs 3.38%, P<0.05) and 2R (1.15% vs 6.76%, P<0.05). Subgroup analysis according to the tumor location distribution showed that in upper thoracic cases, there was no statistical difference in LNM rates among stations no matter whether patients received NCT or NCRT or NICT. NICT group had higher LNM rates in station 2R (9.1%) in middle thoracic cases (P<0.05) and in station 18 (7.5%) (P<0.05) in lower thoracic cases, compared with the NCRT group and NCT group.

CONCLUSION

NCRT or NICT followed by surgery may result in a promising pCR rate and show a better performance in therapeutic response of primary lesion. No matter whether patients received NCT or NCRT or NICT, multiple level and skip node metastases are common, and adequate lymphadenectomy should be achieved to ensure the complete removal of metastatic lymph nodes.

Low Dose Fractionated Radiation Therapy as a Chemo-Potentiator of Salvage Temozolomide (TMZ) for Recurrent Anaplastic Astrocytoma (AA) and Glioblastoma Multiforme (GBM): A Single-Arm Phase I/II Trial

PURPOSE/OBJECTIVE(S)

Cell survival curves demonstrate low-dose radiation hypersensitivity, with steepest cell kill at 0.3-0.5 Gy/fx. This phase 1/2 study assessed the safety and efficacy of low-dose fractionated radiation therapy (LDFRT) as a chemopotentiator of concurrent TMZ for patients with recurrent GBM or AA.

MATERIALS/METHODS

Patients with recurrent GBM or AA s/p standard of care therapy and ≥12 months from prior RT and ≥2 months from prior TMZ were eligible to receive 0.5 Gy of RT twice daily for 10 fx with concurrent TMZ (150-200 mg/m2), both delivered in 5 consecutive days of a 28-day cycle for up to 6 cycles, followed by 6 more cycles of adjuvant TMZ. In phase 1, hematologic toxicity was assessed 1 month after starting therapy. Brain MRIs were obtained every 2 months, or every 1 month in cases of potential progression. Progression was defined by RANO criteria. Pseudoprogression consisted of MRI changes independent of clinical deterioration or steroid use that stabilize/reverse without oncologic intervention. The primary endpoint was 1-year overall survival (OS), with a lower bound of an 80% CI >28% deemed promising for further study based on historical data. Secondary endpoints were rates of pseudoprogression and hematologic toxicity.

RESULTS

Thirty-one patients were enrolled/analyzed. Grade 3-4 acute hematologic toxicity was seen in 8 (27%) patients. Median follow-up was 9.5 (range: 0.1-66.3) months (mos). Median and 1-yr OS were 9.6 (95% CI = 7.0-15.4) mos and 34.5% (95% CI = 20.9%-57.0%). The lower bound of the 80% CI for 1-yr OS was 24.8%. 77% of patients experienced pseudoprogression, with a median time to pseudoprogression from start of LDFRT of 1.9 (95% CI = 1.7-4.4) mos and median duration of 3.6 (95% CI = 1.6-Not estimable) mos. Patients with pseudoprogression had improved OS vs. those without (N = 6; median 10.6 vs 3.9 mos, HR = 0.12 [95% CI = 0.03-0.40]; P < 0.01).

CONCLUSION

LDFRT in the re-irradiation setting for GBM or AA was safe. High rates of pseudoprogression were observed at strikingly low RT doses, with improved OS amongst patients with vs. without pseudoprogression. While pseudoprogression is common at definitive doses of brain RT, it is rare at palliative doses (e.g., 30 Gy/10 fx). Thus, low-dose RT hypersensitivity may be elicited by LDFRT with TMZ for patients with GBM/AA. Further study is needed to optimally apply this radiobiological property to improve patient outcomes.

Patterns of Failure in Pediatric and Young Adult Rhabdomyosarcoma

PURPOSE/OBJECTIVE(S)

To characterize patterns of failure in pediatric and young adult patients with rhabdomyosarcoma (RMS) from a single institution with over 20 years of experience.

MATERIALS/METHODS

Patients diagnosed with RMS from 2000 to 2022 were identified retrospectively. Time to failure was calculated from diagnosis. Local only failure was defined as first failure at the primary site without distant failure. Distant failure was defined as first failure outside of the primary site with or without local failure. Cumulative incidence (CI) of failure was calculated using death as a competing risk. Fine-Gray regression was used to evaluate impact of prognostic factors.

RESULTS

Ninety-five patients were eligible. Median age was 7.28 years (range 0 - 35 years), 41% of patients were >10 years old. Median follow up was 33.3 months. Approximately half (n = 47, 49.5%) of the tumors demonstrated alveolar histology. FOXO1 fusion status was available in 76 (80%) patients, of which 7 out of 37 alveolar tumors (18.9%) were FOXO1 fusion negative. The majority of tumors presented with unfavorable primary site (n = 72, 75.8%) and advanced stage (Stage III and IV, n = 72, 75.8%). The 5-yr CI of local only failure and distant failure for the entire cohort was 19.0% (95% CI 11.3, 28.3) and 34.6% (24.0, 45.5%), respectively. The predominant pattern of failure by Group was: Groups 1&2: Local only (5yr CI 14.8%), Group 3: Distant (5yr CI: 25.9%), Group 4: Distant (5yr CI: 67.6%). CI of distant failure by primary site was higher in perianal/gluteal (n = 2/5, 5yr CI 60.0%) and extremity (n = 8/19, 5yr CI 45.9%) sites. Of the 28 distant failures, 10 (36%) also had a local failure component. CI of local only failure by primary site was higher in parameningeal head and neck (n = 6/25, 5yr CI 30%) and bladder/prostate (n = 2/12, 5yr CI 23%) sites. The following were associated with an increased CI of distant failures: increasing age (HR 1.08, p<0.01), alveolar vs. embryonal histology (HR 3.01, p = 0.0095), FOXO1 fusion positive vs. negative (HR 2.8, p = 0.02) and Group IV vs. Groups I/II (HR 7.7, p = 0.0007). FOXO1 fusion and alveolar histology were associated with older age and Group IV, both of which were independently associated with increased distant failure on multivariate analysis.

CONCLUSION

Failures were predominantly distant in older patients and patients with Group IV RMS, both of which were associated with FOXO1 fusion and alveolar histology, highlighting the need to improve therapies in this population. Local only failures were highest in parameningeal head and neck and bladder/prostate primaries, highlighting the need to improve local control strategies at these sites.

Reciprocal inhibition of PIN1 and APC/CCDH1 controls timely G1/S transition and creates therapeutic vulnerability

Cyclin-dependent kinases (CDKs) mediated phosphorylation inactivates the anaphase-promoting complex (APC/CCDH1), an E3 ubiquitin ligase that contains the co-activator CDH1, to promote G1/S transition. PIN1 is a phosphorylation-directed proline isomerase and a master cancer signaling regulator. However, little are known about APC/CCDH1 regulation after phosphorylation and about PIN1 ubiquitin ligases. Here we uncover a domain-oriented reciprocal inhibition that controls the timely G1/S transition: The non-phosphorylated APC/CCDH1 E3 ligase targets PIN1 for degradation in G1 phase, restraining G1/S transition; APC/CCDH1 itself, after phosphorylation by CDKs, is inactivated by PIN1-catalyzed isomerization, promoting G1/S transition. In cancer, PIN1 overexpression and APC/CCDH1 inactivation reinforce each other to promote uncontrolled proliferation and tumorigenesis. Importantly, combined PIN1- and CDK4/6-inhibition reactivates APC/CCDH1 resulting in PIN1 degradation and an insurmountable G1 arrest that translates into synergistic anti-tumor activity against triple-negative breast cancer in vivo. Reciprocal inhibition of PIN1 and APC/CCDH1 is a novel mechanism to control timely G1/S transition that can be harnessed for synergistic anti-cancer therapy.

Inhibition of CK1ε potentiates the therapeutic efficacy of CDK4/6 inhibitor in breast cancer

Although inhibitors targeting CDK4/6 kinases (CDK4/6i) have shown promising clinical prospect in treating ER+/HER2- breast cancers, acquired drug resistance is frequently observed and mechanistic knowledge is needed to harness their full clinical potential. Here, we report that inhibition of CDK4/6 promotes βTrCP1-mediated ubiquitination and proteasomal degradation of RB1, and facilitates SP1-mediated CDK6 transcriptional activation. Intriguingly, suppression of CK1ε not only efficiently prevents RB1 from degradation, but also prevents CDK4/6i-induced CDK6 upregulation by modulating SP1 protein stability, thereby enhancing CDK4/6i efficacy and overcoming resistance to CDK4/6i in vitro. Using xenograft and PDX models, we further demonstrate that combined inhibition of CK1ε and CDK4/6 results in marked suppression of tumor growth in vivo. Altogether, these results uncover the molecular mechanisms by which CDK4/6i treatment alters RB1 and CDK6 protein abundance, thereby driving the acquisition of CDK4/6i resistance. Importantly, we identify CK1ε as an effective target for potentiating the therapeutic efficacy of CDK4/6 inhibitors.

Targeting Pin1 renders pancreatic cancer eradicable by synergizing with immunochemotherapy

Pancreatic ductal adenocarcinoma (PDAC) is characterized by notorious resistance to current therapies attributed to inherent tumor heterogeneity and highly desmoplastic and immunosuppressive tumor microenvironment (TME). Unique proline isomerase Pin1 regulates multiple cancer pathways, but its role in the TME and cancer immunotherapy is unknown. Here, we find that Pin1 is overexpressed both in cancer cells and cancer-associated fibroblasts (CAFs) and correlates with poor survival in PDAC patients. Targeting Pin1 using clinically available drugs induces complete elimination or sustained remissions of aggressive PDAC by synergizing with anti-PD-1 and gemcitabine in diverse model systems. Mechanistically, Pin1 drives the desmoplastic and immunosuppressive TME by acting on CAFs and induces lysosomal degradation of the PD-1 ligand PD-L1 and the gemcitabine transporter ENT1 in cancer cells, besides activating multiple cancer pathways. Thus, Pin1 inhibition simultaneously blocks multiple cancer pathways, disrupts the desmoplastic and immunosuppressive TME, and upregulates PD-L1 and ENT1, rendering PDAC eradicable by immunochemotherapy.

Randomised clinical trial: faecal microbiota transplantation for recurrent Clostridum difficile infection - fresh, or frozen, or lyophilised microbiota from a small pool of healthy donors delivered by colonoscopy

BACKGROUND

Faecal microbiota transplantation (FMT) has become routine in managing recurrent C. difficile infection (CDI) refractory to antibiotics.

AIM

To compare clinical response and improvements in colonic microbiota diversity in subjects with recurrent CDI using different donor product.

METHODS

Seventy-two subjects with ≥3 bouts of CDI were randomised in a double-blind study to receive fresh, frozen or lyophilised FMT product via colonoscopy from 50 g of stool per treatment from eight healthy donors. Recipients provided stools pre- and 7, 14 and 30 days post-FMT for C. difficile toxin and, in a subset, microbiome composition by 16S rRNA gene profiling.

RESULTS

Overall resolution of CDI was 87% during 2 months of follow-up after FMT. Stool samples before FMT had significantly decreased bacterial diversity with a high proportion of Proteobacteria compared to donors. Cure rates were highest for the group receiving fresh product seen in 25/25 (100%), lowest for the lyophilised product 16/23 (78%; P = 0.022 vs. fresh and 0.255 vs. frozen) and intermediate for frozen product 20/24 (P = 0.233 vs. fresh). Microbial diversity was reconstituted by day 7 in the subjects receiving fresh or frozen product. Improvement in diversity was seen by day 7 in those randomised to lyophilised material with reconstitution by 30 days.

CONCLUSIONS

Comparative efficacy in faecal microbiota transplantation was observed in subjects receiving fresh or frozen faecal product from the same donors. The lyophilised product had a slightly lowered efficacy compared with fresh product, but it resembled other treatments in microbial restoration 1 month after faecal microbiota transplantation.

Erythrocytosis in hepatocellular carcinoma portends poor prognosis by respiratory dysfunction secondary to mitochondrial DNA mutations

Erythrocytosis is a common paraneoplastic syndrome associated with hepatocellular carcinoma. Although increased erythropoietin (EPO) is found in these patients, the clinical significance and molecular mechanisms underlying this observation are unclear. We demonstrate an inverse relationship between EPO production and overall prognosis in our cohort of 664 patients as well as in data from The Cancer Genome Atlas. In the subset of hepatocellular carcinoma patients with erythrocytosis, we identified somatic mutations of mitochondrial DNA, resulting in impairment of respiratory metabolism, which sequentially led to depletion of α-ketoglutarate, stabilization of hypoxia inducible factor-α, and expression of target genes such as EPO. Cell lines and patient-derived xenograft models were used to demonstrate that EPO promoted cancer stem cell self-renewal and expansion in an autocrine/paracrine manner through enhanced Janus kinase/signal transducer and activator of transcription signaling both in vitro and in vivo. Furthermore, to explore the therapeutic targeting of EPO-induced tumor changes, we found that blocking EPO signaling with soluble EPO receptor extracellular domain Fc fusion protein could inhibit tumor growth both in vitro and in vivo.

CONCLUSION

These findings suggest clinical and therapeutic implications for erythrocytosis in hepatocellular carcinoma. There is an underlying link between mitochondrial function and hypoxia inducible factor alpha signaling, revealing a mechanism of erythrocytosis in a subset of hepatocellular carcinoma patients who may benefit from treatment involving EPO signaling interference. (Hepatology 2017;65:134-151).

Genome-wide association studies identify susceptibility loci affecting respiratory disease in Chinese Erhualian pigs under natural conditions

Prevalence of swine respiratory disease causes poor growth performance in and serious economic losses to the swine industry. In this study, a categorical trait of enzootic pneumonia-like (EPL) score representing the infection gradient of a respiratory disease, more likely enzootic pneumonia, was recorded in a herd of 332 Chinese Erhualian pigs. According to their EPL scores and the disease effect on weight gains, these pigs were grouped into controls (EPL score ≤ 1) and cases (EPL score > 1). The weight gain of the case group reduced significantly at days 180, 210, 240 and 300 as compared to the control group. The heritability of EPL score was estimated to be 0.24 based on the pedigree information using a linear mixed model. All 332 Erhualian pigs and their nine sire parents were genotyped with Illumina Porcine 60K SNP chips. Two genome-wide association studies were performed under a generalized linear mixed model and a case-control model respectively. In total, five loci surpassed the suggestive significance level (P = 2.98 × 10^-5 ) on chromosomes 2, 8, 12 and 14. CXCL6, CXCL8, KIT and CTBP2 were highlighted as candidate genes that might play important roles in determining resistance/susceptibility to swine EP-like respiratory disease. The findings advance understanding of the genetic basis of resistance/susceptibility to respiratory disease in pigs.

A single fas gene mutation changes lupus onset, severity, location, and molecular abnormalities in mice

Although genetic predisposition plays a major role in the progression of systemic lupus erythematosus (SLE) and its variation in symptoms, the precise relationships between genetic changes and disease status are not well understood. Here, to demonstrate the effect of a single gene mutation on disease etiology, we examined two mouse models of SLE with the same genetic background but different Fas genes. Mice with the Fas(lpr) gene developed severe SLE with renal dysfunction and inflammatory responses in the lung and kidney. By contrast, mice with the Fas(+) gene showed disease-related abnormalities in the liver and joints. Patterns of inflammatory disease markers differed across organs between the two lines of mice. Fas(lpr) mice showed greater MMP signals in the kidney and IL-11 signals in the lung than Fas(+) mice. Fas(+) mice had higher IL-11 signal intensity in the knee region and higher CXCR4 signal intensity in the liver than Fas(lpr) mice. Our results exemplify the complexity of disease and suggest the need for individualized target-specific treatment regimens. Strengths and Limitations of this Study: Fas gene is a well characterized gene in this disease. The molecular components in human disease need more clinical data.

Identification of the putative binding pocket of valerenic acid on GABAA receptors using docking studies and site-directed mutagenesis

Background and Purpose

β2/3‐subunit‐selective modulation of GABA_A receptors by valerenic acid (VA) is determined by the presence of transmembrane residue β2/3N265. Currently, it is not known whether β2/3N265 is part of VA's binding pocket or is involved in the transduction pathway of VA's action. The aim of this study was to clarify the localization of VA's binding pocket on GABA_A receptors.

Experimental Approach

Docking and a structure‐based three‐dimensional pharmacophore were employed to identify candidate amino acid residues that are likely to interact with VA. Selected amino acid residues were mutated, and VA‐induced modulation of the resulting GABA_A receptors expressed in Xenopus oocytes was analysed.

Key Results

A binding pocket for VA at the β⁺/α⁻ interface encompassing amino acid β3N265 was predicted. Mutational analysis of suggested amino acid residues revealed a complete loss of VA's activity on β3M286W channels as well as significantly decreased efficacy and potency of VA on β3N265S and β3F289S receptors. In addition, reduced efficacy of VA‐induced I_GABA enhancement was also observed for α1M235W, β3R269A and β3M286A constructs.

Conclusions and Implications

Our data suggest that amino acid residues β3N265, β3F289, β3M286, β3R269 in the β3 subunit, at or near the etomidate/propofol binding site(s), form part of a VA binding pocket. The identification of the binding pocket for VA is essential for elucidating its pharmacological effects and might also help to develop new selective GABA_A receptor ligands.

Multiple target-specific molecular agents for detection and image analysis of breast cancer characteristics in mice

Breast cancer is a heterogenetic tumor at the cellular level with multiple factors and components. The inconsistent expression of molecular markers during disease progression reduces the accuracy of diagnosis and efficacy of target-specific therapy. Single target-specific imaging agents can only provide limited tumor information at one time point. In contrast, multiple target-specific imaging agents can increase the accuracy of diagnosis. The aim of this study was to demonstrate the ability of multi-agent imaging to discriminate such differences in single tumor. Mice bearing human cancer cell xenografts were tested to determine individual differences under optimal experimental conditions. Neovasculature agent (RGD peptide), tumor stromal agent (matrix metalloproteinase), and tumor cell markers (epidermal growth factor, Her-2, interleukin 11) imaging agents were labeled with reporters. 18F-Fluorodeoxyglucose was used to evaluate the tumor glucose status. Optical, X-ray, positron emission tomography, and computer tomography imaging modalities were used to determine tumor characteristics. Tumor size and imaging data demonstrated that individual differences exist under optimal experimental conditions. The target-specific agents used in the study bind to human breast cancer cell lines in vitro and xenografts in vivo. The pattern of binding corresponds to that of tumor markers. Multi-agent imaging had complementary effects in tumor detection. Multiple noninvasive imaging agents and modalities are complementary in the interrogation of unique biological information from each individual tumor. Such multi-agent approaches provide methods to study several disease components simultaneously. In addition, the imaging results provide information on disease status at the molecular level.

Multiple target-specific molecular imaging agents detect liver cancer in a preclinical model

Liver cancer is the fifth most common cause of cancer deaths worldwide. Noninvasive diagnosis is difficult and the disease heterogeneity reduces the accuracy of pathological assays. Improvement in diagnostic imaging of specific molecular disease markers has provided hope for accurate and early noninvasive detection of liver cancer. However, all current imaging technologies, including ultrasonography, computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging, are not specific targets for detection of liver cancer. The aim of this study was to test the feasibility of injecting a cocktail of specific molecular imaging agents to noninvasively image liver cancer. The target-specific cocktail contained agents for imaging the neovasculature (RGD peptide), matrix metalloproteinase (MMP), and glucose transport (¹⁸F-fluorodeoxyglucose [¹⁸F-FDG]). Imaging studies were performed in liver cancer cells and xenograft models. The distribution of MMP at the intracellular level was imaged by confocal microscopy. RGD, MMP, and ¹⁸F-FDG were imaged on tumor-bearing mice using PET, CT, X-ray, and multi-wavelength optical imaging modalities. Image data demonstrated that each agent bound to a specific disease target component. The same liver cancer xenograft contained multiple disease markers. Those disease markers were heterogenetically distributed in the same tumor nodule. The molecular imaging agents had different distributions in the whole body and inside the tumor nodule. All target-specific agents yielded high tumor-to-background ratios after injection. In conclusion, target-specific molecular imaging agents can be used to study liver cancer in vitro and in vivo. Noninvasive multimodal/multi-target-specific molecular imaging agents could provide tools to simultaneously study multiple liver cancer components.

Heme oxygenase-1: a molecular brake on hepatocellular carcinoma cell migration

Hepatocellular carcinoma (HCC) is a fatal disease with great public health impact worldwide. Heme oxygenase (HO)-1 has recently been reported as an important player in tumor angiogenesis and metastasis. However, the role of HO-1 in liver cancer metastasis is unclear. In this study, we explored genetic differences and downstream signal transduction pathways of HO-1 in liver cancer cell lines. HO-1 wild-type and mutant cell lines were generated from human liver cancer cell line HepG2. The overexpression of wild-type HO-1 decreased the migration of HepG2 cells. In contrast, the overexpression of mutant HO-1G143H increased the migration of the cancer cells. Interleukin (IL)-6 is one of the major downstream molecules that mediated this process because IL-6 expression and migration are suppressed by HO-1 and increased when HO-1 is knocked down by shRNA. In addition, we demonstrated carbon monoxide (CO) and p38MAPK are the cofactors in this signal pathway. In vivo animal model demonstrated HO-1 inhibited the tumor growth. In conclusion, in vitro and in vivo data show HO-1 inhibits the human HCC cells migration and tumor growth by suppressing the expression of IL-6. The heme degradation product CO is a cofactor in this process and inhibits p38MAPK phosphorylation.

Pregnane X receptor suppresses proliferation and tumourigenicity of colon cancer cells

BACKGROUND

Pregnane X receptor (PXR) is a nuclear receptor that regulates the metabolism and disposition of various xenobiotics and endobioitics. We investigated a novel PXR function in regulating colon tumourigenesis in this study.

METHODS

Histochemistry, transfection, cell proliferation assay, anchorage-alpha-dependent assay, xenograft, immunohistochemistry, immunofluorescence flow cytometry.

RESULTS

Using histochemistry analysis, we found that PXR expressions were lost or greatly diminished in many colon tumours. Ectopic expression of human PXR through stable transfection of PXR into colon cancer cell line HT29 significantly inhibited cell proliferation as determined by cell proliferation assay and anchorage-independent assay. Pregnane X receptor suppressed significantly HT29 xenograft tumour growth in nude mice compared with control (310+/-6.2 vs 120+/-6 mg, P<0.01). Immunohistochemistry and immunofluorescence analysis of Ki-67 on excised xenograft tumour tissues showed that PXR inhibited cancer cell proliferation. Furthermore, expressions of PXR and Ki-67 were mutually exclusive. The flow cytometry analysis indicated that PXR caused G(0)/G(1) cell-cycle arrest. p21(WAF1/CIP1) expression was markedly elevated whereas E2F1 expression was inhibited by PXR.

CONCLUSION

PXR inhibits the proliferation and tumourigenicity of colon cancer cells by controlling cell cycle at G(0)/G(1) cell phase by regulating p21(WAF1/CIP1) and E2F/Rb pathways.

Multimodal optical molecular image reconstruction with frequency domain measurements

Multimodality molecular imaging is becoming more and more important to understand both the structural and the functional characteristics of tissue, organs and tumors. So far, invasive nuclear methods utilizing ionizing radiation have been the "gold standard" of molecular imaging. We investigate non-contact, non-invasive, patient-tolerant and inexpensive near infrared (NIR) frequency domain optical tomography (FDOT) as a functional complement to structural X-ray computed tomography (CT) data. We show a novel multifrequency NIR FDOT approach both in transmission and reflectance mode and employ radiative transport equation (RTE) for 3D reconstruction of a target with novel fluorescent gold nanoshell indocyanine green (NS ICG) in an ex vivo nude mouse. The results demonstrate that gold NS ICG with multifrequency NIR FDOT is a promising fluorophore for multimodal optical molecular image reconstruction.

Synthesis and characterization of branched poly(l-glutamic acid) as a biodegradable drug carrier

Polymeric drug delivery systems are used not only to improve aqueous solubility of drug molecules but also to achieve desirable pharmacokinetics and an enhanced therapeutic index. New biodegradable polymers are needed to improve the biodistribution and targeting-ability of polymeric carriers. In this study, the synthesis and characterization of branched poly(L-glutamic acid) (PG) containing multiple PG chains centered on a poly(amidoamine) (PAMAM) dendrimer or polyethyleneimine (PEI) cores were described. The branched PG polymers were obtained by ring-opening polymerization of benzyl ester of L-glutamic acid N-carboxyanhydride using PAMAM or PEI as the initiator. These polymers were degradable in the presence of the lysosomal enzyme cathepsin B, albeit more slowly than linear PG. Unlike conventional linear PG, each branched PG possessed multiple terminal amino groups. This made it possible to attach multiple targeting moieties selectively to the termini of branched PG. Conjugation of monofunctional or heterodifunctional polyethylene glycol to the chain ends of branched PG was demonstrated in the presence of side chain carboxyl groups. Furthermore, folic acid, a model targeting moiety, and the near-infrared dye indocyanine green, a model diagnostic agent, were successfully conjugated to the terminal amino groups and the side chain carboxyl groups of branched PG, respectively. The resulting conjugate had reduced nonspecific interaction and bound selectively to tumor cells expressing folate receptors. Thus, branched PG may be useful as a polymeric carrier for targeted drug delivery.

Mechanism of suppression of cytochrome P-450 1A1 expression by tumor necrosis factor-alpha and lipopolysaccharide

Proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, interleukin-1beta, and lipopolysaccharides (LPS), suppress the gene expression of cytochrome P-450 1A1 (cyp1a1). The mechanism of the suppression is not well understood. In present study, we show that activation of nuclear factor-kappaB (NF-kappaB) is a critical event leading to the suppression of cyp1a1 gene expression, thus providing an underlying mechanism for the TNF-alpha- and LPS-induced cyp1a1 suppression. We demonstrated that: (i) inducible RelA expression down-regulated aryl hydrocarbon receptor (AhR) activated reporter gene; (ii) the suppressive effects of LPS and TNF-alpha on the AhR-activated reporter gene could be blocked by pyrrolidine dithiocarbamate, which is known to inhibit NF-kappaB action; and (iii) TNF-alpha and LPS-imposed repression could be reversed by the NF-kappaB super repressor (SRIkappaBalpha), thus demonstrating the specific involvement of NF-kappaB. Furthermore, nuclear receptor coactivators p300/CBP and steroid receptor coactivator-1 act individually as well as cooperatively to reverse the suppressive effects by NF-kappaB on the AhR-activated reporter gene, suggesting that these transcriptional coactivators serve as the common integrators for the two pathways, thereby mediating the cross-interactions between AhR and NF-kappaB. Finally, using the chromatin immunoprecipitation assay, we demonstrated that AhR ligand induces histone H4 acetylation at the cyp1a1 promoter region containing the TATA box, whereas TNF-alpha inhibits this acetylation, suggesting that AhR/NF-kappaB interaction converges at level of transcription involving chromatin remodeling.

Conjugation with (111)In-DTPA-poly(ethylene glycol) improves imaging of anti-EGF receptor antibody C225

Significant liver uptake often limits the clinical application of radiolabeled antibodies in radioimmunodetection. The purpose of this study was to evaluate the gamma-imaging properties of an antiepidermal growth factor receptor (EGFR) antibody, C225, conjugated with heterofunctional poly(ethylene glycol) (PEG) with 1 terminus of the polymer attached to a radiometal chelator, diethylenetriaminepentaacetic acid (DTPA).

METHODS

Two preparations of PEG-modified C225, one with 20% and the other with 60% amine substitution, were labeled with (111)In. The conjugates, (111)In-DTPA-PEG-C225, were injected intravenously into nude mice with EGFR-positive A431 tumors. For comparison, C225 directly labeled with (111)In was also injected. In a competitive study, mice with A431 tumors were pretreated intravenously with 100-fold excess of native C225, followed by an injection of (111)In-DTPA-PEG-C225 30 min or 20 h later. In addition, (111)In-DTPA-PEG-C225 was injected into mice with EGFR-positive MDA-MB-468 tumors and EGFR-negative MDA-MB-435 tumors. Images were acquired at 5 min and at 2, 6, 24, and 48 h after injection of the radiotracers. Regions of interest (ROIs) were drawn on the computer images around the whole body, liver, muscle, and tumor. The counts per pixel in the tumor and normal tissues were calculated. At 48 h, the mice were killed and dissected. Blood, liver, muscle, and tumor samples were removed and the radioactivity of each sample was measured.

RESULTS

In A431 tumor xenografts, the tumor uptake of C225 modified with PEG was not significantly different than the uptake of unmodified (111)In-DTPA-C225. Uptake in the liver, however, was reduced by 38%-45%, and the reduction increased with increasing degree of PEG substitution. Tumors of A431 and MDA-MB-468 xenografts were clearly visualized with (111)In-DTPA-PEG-C225, whereas tumors of the MDA-MB-435 xenograft, which expresses low levels of EGFR, were not as readily visible. The tumor-to-blood ratios of (111)In-DTPA-PEG-C225 in A431 and MDA-MB-468 xenografts were about 3 fold higher than in MDA-MB-435 xenografts. Blocking EGFR by pretreatment with native C225 significantly reduced the uptake of (111)In-DTPA-PEG-C225 in the liver. The tumor-to-blood ratios in mice with A431 tumors were decreased 2.5-2.7 fold after pretreatment with a large excess of C225. Similar results were obtained with MDA-MB-468 tumor xenografts. In contrast, the tumor-to-blood ratios in mice with MDA-MB-435 tumor xenografts were not significantly different in C225-pretreated mice than in nonpretreated mice.

CONCLUSION

These findings indicate that (111)In-DTPA-PEG-C225 selectively localized to the tumors expressing high levels of EGFR. PEG-modification of C225 significantly reduced its liver uptake, resulting in improved visualization of EGFR-positive tumors. Using PEG as a linker between the monoclonal antibody and metal chelator is a useful strategy to optimize the imaging characteristics of antibody-based scintigraphic agents.

Potentiation of radioresponse by polymer-drug conjugates

Although combined chemotherapy and radiotherapy has produced significantly improved response and survival rates among cancer patients, there is still a compelling need to establish the most effective way to deliver these agents. We hypothesize that the radiosensitizing effect of a chemotherapeutic agent can be further enhanced if the drug is delivered at an optimal concentration and is maintained in the tumor for a prolonged period. Using a water-soluble poly(L-glutamic acid)-conjugated paclitaxel (PG-TXL) as a model compound, we investigated whether paclitaxel delivered by means of polymeric carrier could increase the tumor's response to radiation. Mice bearing 8-mm syngeneic ovarian carcinoma OCa-1 tumors implanted intramuscularly were treated with i.v. injected PG-TXL alone or in combination with single doses of local radiation. The enhancement factors at 24 h interval, as measured by incremental tumor growth delay compared with radiation alone, ranged from 2.48 to 4.28. The values varied as a function of radiation dose. The enhancement of radioresponse is also a function of time interval between injection of PG-TXL and tumor irradiation. The enhancement factor increased with decreasing interval, suggesting that radiation may in turn mediate the sensitivity of tumor toward PG-TXL. Thus, the mechanism of PG-TXL's radiopotentiation activity is probably multifactorial. Remarkably, while combined radiation and TXL produced additive or even sub-additive interaction when radiation preceded TXL injection, combined radiation and PG-TXL produced synergistic interaction in a mammary MCa-4 tumor model. Radiation significantly increased tumor uptake of PG-TXL, suggesting a potential role of radiation-modulated antitumor activity of polymeric drugs. Our data support a treatment strategy combining radiation and polymeric chemotherapy that may have important clinical implications in terms of scheduling and optimization of the therapeutic ratio.

Biodistribution of paclitaxel and poly(L-glutamic acid)-paclitaxel conjugate in mice with ovarian OCa-1 tumor

PURPOSE

Poly(L-glutamic acid)-paclitaxel (PG-TXL) is a water-soluble paclitaxel (TXL) conjugate made by conjugating TXL to poly(L-glutamic acid) via ester bonds. In preclinical studies, PG-TXL has shown significant antitumor activity against a variety of solid tumors. To elucidate the relationship between tissue distribution and antitumor efficacy of PG-TXL, we studied and compared the biodistribution of PG-TXL and TXL.

METHODS

Female C3Hf/Kam mice bearing syngeneic ovarian OCa-1 tumors were injected with either [3H]TXL or PG-[3H]TXL at an equivalent TXL dose of 20 mg/kg. Mice were killed at various times after drug injection, and samples of blood, spleen, liver, kidney, lung, heart, muscle, brain, fat, and tumor were removed and the radioactivity counted. In addition, concentrations of free [3H]TXL released from PG-[3H]TXL in the spleen, liver, kidney, and tumor were analyzed by using high-performance liquid chromatography (HPLC). Whole-body autoradiographs of mice killed 1 day and 6 days after administration of PG-[3H]TXL were obtained to study the intratumoral distribution of PG-TXL.

RESULTS

When [3H]TXL was conjugated to polymer, the biodistribution pattern of PG-[3H]TXL differed from that of [3H]TXL. Based on area under the tissue concentration-time curve (AUC) values, tumor exposure to [3H]TXL was five times greater when administered as PG-TXL than as TXL formulated in Cremophor EL/alcohol vehicle. Furthermore, concentrations of free paclitaxel released from PG-[3H]TXL remained relatively constant in tumor tissue, being 489, 949 and 552 ng/g tumor tissue at 5, 48 and 144 h after dosing, respectively. Autoradiographic images of mice injected with PG-[3H]TXL revealed that radioactivity was primarily located in the periphery of the tumor on day 1 after drug administration and was homogeneously diffused into the center of the tumor by day 6. Over the 144-h study period, [3H]TXL concentrations, predominantly as the inactive conjugate, were higher in tissues with a more abundant reticular endothelial system (i.e. liver, kidney, spleen, lung) than in tissues with less abundant or lacking RE systems (i.e. muscle, fat, brain). Both [3H]TXL and PG-[3H]TXL were excreted primarily through the hepatobiliary route, with a small fraction of each drug (5% and 8.7%, respectively) excreted into the urine within 48 h.

CONCLUSIONS

This study indicates that the distribution to tumor tissue was enhanced when [3H]TXL was administered as a macromolecular conjugate, and that free TXL was released and maintained within the tumor for a prolonged period. Thus, the antitumor activity of PG-TXL observed in preclinical studies may be attributed in part to enhanced tumor uptake of PG-TXL.

Calcining influence on the powder properties of hydroxyapatite

The effect of different calcination temperatures on the powder characteristics and the sintered density of synthetic hydroxyapatite (HA) powders, produced using two different processing routes, was examined. Powders were produced by either drying, milling and sieving an as-precipitated HA or by spray-drying a slurry of precipitated HA. Calcining the two powders at temperatures between 400 and 1000 degrees C did not significantly affect the powder particle size. The specific surface areas of the two powders, however, were reduced from 70-80 m2/g for a calcination temperature of 400 degrees C to approximately 5-7 m2/g for 1000 degrees C. Analysis of the surfaces of the HA powders using scanning electron microscopy (SEM) illustrated the coarsening and subsequent sintering of the sub-micron crystallites that constitute a powder particle as the calcination temperature increased, corresponding to the decrease in surface area of the powders. The sintered densities of the final ceramics were not significantly affected by calcining the powders. Microhardness measurements of ceramics prepared from powders calcined at different temperatures showed no significant variations with calcination temperature or powder processing method. The results of this study have illustrated that for applications where HA may be used in powder form, for example in plasma-spraying and for the production of HA-polymer composites, calcining the HA will significantly affect the powder properties, namely the surface area and morphology of the powders. For applications requiring HA in a dense ceramic form, for example as granules or blocks, calcining the powders does not significantly affect the properties of the final ceramic.

Effect of powder characteristics on the sinterability of hydroxyapatite powders

The effect of different sintering conditions on the sintered density and microstructure of two different hydroxyapatite (HA) powders was examined. The powder characteristics of a laboratory synthesized HA powder (Lab HA) were low crystallinity, a bimodal particle size distribution, a median particle size of 22 microm and a high specific surface area (SSA) of 63 m2/g. By contrast, a commercial calcined HA (commercial HA) was crystalline and had a median particle size of 5 microm and a low SSA of 16 m2/g. The different powder characteristics affected the compactability and the sinterability of the two HA powders. Lab HA did not compact as efficiently as commercial HA, resulting in a lower green density, but the onset of sintering of powder compacts of the former was approximately 150 degrees C lower than the later. The effect of compaction pressure, sintering temperature, time and heating rate on the sintered densities of the two materials was studied. Varying all these sintering conditions significantly affected the sintered density of commercial HA, whereas the sintered density of Lab HA was only affected significantly by increasing the sintering temperature. The Vickers hardness, Hv, of Lab HA was greater than commercial HA for low sintering temperatures, below 1200 degrees C, whereas for higher sintering temperatures the commercial HA produced ceramics with greater values of hardness. These trends can be related to the sinterability of the two materials.

Potentiation of ovarian OCa-1 tumor radioresponse by poly (L-glutamic acid)-paclitaxel conjugate

PURPOSE

It has been shown that paclitaxel (TXL) can strongly enhance tumor cells' sensitivity to radiation. We examined whether the radiosensitizing effect of paclitaxel can be further enhanced when it is delivered systemically as a polymer-drug conjugate that provides enhanced tumor uptake and prolonged release of TXL in the tumor.

METHODS AND MATERIALS

C3Hf/Kam mice bearing 8-mm murine ovarian OCa-1 tumors were treated with i.v.-injected Poly(L-glutamic acid)-paclitaxel (PG-TXL) at an equivalent TXL dose of 80 mg/kg, followed 24 h later by single doses of local radiation ranging from 5 to 15 Gy. To determine how long the radiopotentiation persisted at extended times after PG-TXL administration, mice with OCa-1 tumors were given i.v. PG-TXL and 4, 24, 48, 72, 120, or 168 h later their tumors were irradiated at a dose of 10 Gy. Antitumor activity was determined by delay in tumor growth. Cell cycle distribution was assayed using flow cytometry. Tumor vascular volume was estimated using Tc-99 m-labeled red blood cells.

RESULTS

PG-TXL strongly potentiated the radioresponse of the OCa-1 tumor. The enhancement factors ranged from 2.79 to 4.28, depending on radiation dose, when PG-TXL preceded radiation by 24 h. The enhancement factor derived from radiation dose-response curves was as high as 5.13. The radiosensitizing effect of PG-TXL was also dependent on the interval between PG-TXL administration and radiation delivery, with greater enhancement been observed when the interval was decreased. The percentage of G2/M cells was significantly increased to 21.4% 48 h after PG-TXL but declined to a preinjection level of 14.8% 72 h after PG-TXL. PG-TXL only moderately increased the tumor vascular volume by 37% 24 h after PG-TXL administration.

CONCLUSION

PG-TXL markedly potentiated response of OCa-1 tumor to radiation. When compared to literature data obtained from the same tumor model used here, PG-TXL exhibited stronger radiosensitization effect than TXL. Although its action is possibly mediated by arrest of cells in G2/M phases of cell cycle and by increased tumor blood supply, PG-TXL may exert its radiopotentiation activity through increased tumor uptake of PG-TXL and sustained release of TXL in the tumor. Our results show that conjugation of TXL to a polymer has the potential to further enhance its radiosensitizing activity and that clinical trials of PG-TXL in combination with radiation is warranted.

Regulation of estrogen receptor mRNA by 2,3,7,8-tetrachlorodibenzo-p-dioxin as measured by competitive RT-PCR

Environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), cause alterations in gene expression. In this study, we measured the regulation of estrogen receptor (ER) mRNA in female CD-1 mice by competitive RT-PCR. Previous work suggests that ER protein levels are affected by TCDD, but how this is regulated is uncertain. These studies found no significant changes in ER mRNA levels, but the methods used (Northern blot analysis and RNase protection assays) lack sensitivity for measuring the low levels of RNA transcript, such as ER mRNA. The method described here offers an excellent alternative for quantifying the changes in mRNA levels. Internal competitors were created with gene-specific primers for ER and beta-actin by PCR reactions at low annealing temperatures. For each sample, the mRNA levels of ER and beta-actin were determined. Using competitive RT-PCR, the relative changes in ER mRNA from TCDD-treated and control animals were determined after normalization with the levels of beta-actin mRNA. The ER mRNA from female CD-1 mice treated with TCDD (single dose 5 micrograms/kg, i.p., 4 days) was found to be significantly suppressed as compared with the vehicle control in all tissues examined. TCDD decreased ER mRNA in the liver (30.1%) as expected. However, the greatest effect was in the reproductive tissues, with a 64.2% reduction in ER mRNA in the ovary. This is the first demonstration that TCDD causes tissue-specific downregulation of ER mRNA. These effects may contribute to the tissue-specific toxicity of TCDD.

In vitro activity and fecal concentration of rifaximin after oral administration

Rifaximin showed moderately high MICs (the MIC at which 90% of the isolates tested were inhibited = 50 microg/ml) for 145 bacterial enteropathogens from patients with traveler's diarrhea acquired in Mexico during the summers of 1997 and 1998. Rifaximin concentrations in stool the day after oral administration (800 mg daily for 3 days) were high (average, 7,961 microg/g), proving the value of the drug.

Tumor irradiation enhances the tumor-specific distribution of poly(L-glutamic acid)-conjugated paclitaxel and its antitumor efficacy

The poly(L-glutamic acid)-paclitaxel (PG-TXL) conjugate has been shown to exhibit significantly greater antitumor activity than conventionally formulated paclitaxel (TXL) against solid tumors (Li et al., Cancer Res., 58: 2404-2409, 1998). Here we report that local tumor irradiation enhanced the distribution of PG-TXL given 24 h later to ovarian OCa-1 carcinoma implanted i.m. in C3Hf/Kam mice. Radiation significantly increased tumor uptake of PG-TXL and tumor vascular permeability, caused elevation of the serum concentration of vascular endothelial growth factor, and arrested OCa-1 cells in the G1 phase of cell cycle. The enhancement factors, as measured by incremental tumor growth delay compared with PG-TXL alone, ranged from 1.36-4.44. Complete tumor regression was also observed at a higher radiation dose (>10 Gy) and a higher PG-TXL dose (>80 mg equivalentTXL/kg). Furthermore, combined radiation and PG-TXL produced a significantly greater tumor growth delay than treatment with radiation and TXL when both drugs were given at the same equivalent TXL dose of 60 mg/kg 24 h after tumor irradiation (enhancement factors, 4.44 versus 1.50). These data suggest that conjugation of TXL to poly(L-glutamic acid) is necessary for improved response and that the supra-additive effect of combined radiation and PG-TXL therapy is due in part to modulation of the enhanced permeability and retention effect of macromolecules by radiation. We propose a treatment strategy combining radiation and macromolecular chemotherapy that may have important clinical implications in terms of scheduling and optimization of the therapeutic ratio.

Cyclic peptides incorporating 4-carboxyphenylalanine and phosphotyrosine are potent inhibitors of pp60(c-)(src)

The protein tyrosine kinase, pp60(c-)(src), is involved in cellular signaling and is activated during mitosis and in various tumors. We have been employing cyclic decapeptides to identify the determinants for substrate binding and phosphorylation to develop inhibitors competitive with protein substrates of Src. A structure-activity study [McMurray, J. S., Budde, R. J. A., Ke, S., Obeyesekere, O. U., Wang, W., Ramdas, L., and Lewis, C. A. (1998) Arch. Biochem. Biophys. 355, 124] revealed that, at the position 3 residues C-terminal to the phosphorylated tyrosine (Y + 3), both glutamic acid and phenylalanine gave identical K(i), K(m), and V(max) values. We hypothesized that the area of Src that binds the Y + 3 residue contains either a positively charged lysine or an arginine, capable of ionic interactions with glutamic acid or cation-pi interactions with phenylalanine. To test this hypothesis, a series of phenylalanine analogues were substituted at position 7 (the Y + 3 residue) in cyclo(Asp(1)-Asn(2)-Glu(3)-Tyr(4)-Ala(5)-Phe(6)-Phe(7)-Gln(8)-D-Phe(9 )-Pro(10)). Of these, 4-carboxyphenylalanine (4-Cpa) and phosphotyrosine resulted in high affinity peptides exhibiting K(i) values of 0.85 and 1.1 microM, respectively, 180- and 130-fold increases in potency over the parent cyclic peptide (K(i) = 150 microM). These peptides were noncompetitive with respect to ATP and competitive against the phosphate-accepting substrate, polyGlu(4)Tyr. The truncated cyclic peptide, cyclo(Phe-4-Cpa-Gln-D-Phe-Pro-Asp-Aca) (Aca = epsilon-aminocaproic acid), which did not contain tyrosine, was also a competitive inhibitor with a K(i) value of 24 microM. We conclude that these cyclic peptides bind to a positively charged area that is near the phosphate transfer region of the active site of Src but does not necessarily include the tyrosine-binding pocket. Furthermore, the 4-Cpa-containing cyclic decapeptide shows remarkable selectivity in the inhibition of Src versus the src family members Yes and Lck, as well as other protein tyrosine kinases, Ser/Thr kinases, and other ATP-utilizing enzymes.

Comparison of action of paclitaxel and poly(L-glutamic acid)-paclitaxel conjugate in human breast cancer cells

The new anticancer agent poly(L-glutamic acid)-paclitaxel (PG-TXL) is a conjugate of paclitaxel and the water-soluble polyglutamate carrier. The observation that PG-TXL appears to possess antitumor activity superior to free paclitaxel in preclinical studies suggests that PG-TXL might possess favorable pharmacokinetic properties and/or have a mechanism of action different from that of paclitaxel. The purpose of this study was to compare the pharmacological action of PG-TXL and free paclitaxel in a panel of breast cancer cell lines with emphasis on their ability to induce apoptosis, their effects on cell cycle progression, and their cellular uptake. Morphological analysis and biochemical characterizations demonstrated that both compounds have similar abilities to induce apoptosis in cells expressing wild-type p53 (MCF-7) or mutant p53 (MDA-MB435 and MDA-MB453). Although MCF-7 cells were less sensitive to each compound than MDA-MB435 and MDA-MB453 cells, transfection experiments demonstrated that p53 did not appear to play a significant role in drug-induced cell death with either agent. Flow cytometry analysis further revealed that both free paclitaxel and PG-TXL induced a characteristic G2/M arrest in the cell cycle, consistent with the disturbance of microtubule polymerization as their mechanism of action. Western blot analysis showed that paclitaxel and PG-TXL downregulated HER2/neu expression in a similar fashion. HPLC analysis revealed that paclitaxel was released from the PG-TXL conjugate in vitro. The released paclitaxel, not the glutamic acid polymer, was subsequently transported into the cells. These results suggest that PG-TXL exerts its anticancer activity by continuous release of free paclitaxel, and that the favorable pharmacokinetics and drug distribution of the PG-TXL conjugate in vivo are likely the main factors contributing to its superior anticancer activity.

[Expression of a HCV multi-epitopes antigen gene and study on its immunogenicity]

Due to the hypervariable character of hepatitis C virus (HCV), 5 conserved T and/or B cell epitopes from core, envelope, NS3 and NS5 protein of HCV were chosen to form a 270 bp multi-epitopes antigen gene. The gene was clone into a fusion vector pWR450-1 to express a beta-galactosidase-HCV hybrid protein GZ-PCX. The purified GZ-PCX protein was specifically recognized by human anti-HCV antibodies. These results show that the HCV hybrid multi-epitopes antigen has excellent immunogenicity, which might be able to be used as an effective diagnosis agent and to provide protectivity to any genotype of HCV which might partly solve the problems in the researches of HCV vaccines.

Antitumor activity of poly(L-glutamic acid)-paclitaxel on syngeneic and xenografted tumors

Poly(L-glutamic acid)-paclitaxel (PG-TXL) is a new water-soluble paclitaxel derivative that has shown remarkable antitumor activity against both ovarian and breast tumors. The purpose of this study was to test whether the antitumor efficacy of PG-TXL depends on tumor type, as is the case for paclitaxel, and to test whether paclitaxel-resistant tumors could be responsive to PG-TXL. We evaluated the therapeutic activity of PG-TXL against four syngeneic murine tumors (MCa-4, MCa-35, HCa-1, and FSa-II) inoculated i.m. into C3Hf/Kam mice, a human SKOV3ip1 ovarian tumor injected i.p. into nude mice, and a human MDA-MB-435Lung2 breast tumor grown in the mammary fat pad of nude mice. Two paclitaxel-responsive murine tumors, MCa-4 and MCa-35, showed significant growth delay with PG-TXL given as a single i.v. injection at its maximum tolerated dose of 160 mg of equivalent paclitaxel/kg or even at a lower dose of 120 mg of equivalent paclitaxel/kg. The other two murine tumors, HCa-1 and FSa-II, did not respond particularly well to either of the two agents, although significant growth delay was observed for both tumors with PG-TXL. In mice with SKOV3ip1 tumors, the median survival times for mice treated with PG alone and PG-TXL at doses of 60 or 120 mg of equivalent paclitaxel/kg were 43, 61, and 75 days, respectively; no survival difference was found between paclitaxel-treated and Cremophor vehicle-treated mice. In mice with MDA-MB-435Lung2 tumor, PG-TXL at a dose of 120 mg of equivalent paclitaxel/kg produced regression of the tumor in 50% of the animals, and in the remaining mice, micrometastases in the lung were found only in 25% of the animals. In comparison, treatment with paclitaxel at 60 mg/kg did not result in tumor regression, and the rate of lung metastases was 42%. These results clearly demonstrate that PG-TXL has significant therapeutic activity against breast and ovarian tumors tested in this study. Future studies to elucidate the mechanism of action of PG-TXL and to assess its clinical applications are warranted.

Ah receptor and NF-kappaB interactions, a potential mechanism for dioxin toxicity

The Ah receptor (AhR) mediates many of the toxic responses induced by polyhalogenated and polycyclic hydrocarbons (PAHs) which are ubiquitous environmental contaminants causing toxic responses in human and wildlife. NF-kappaB is a pleiotropic transcription factor controlling many physiological functions adversely affected by PAHs, including immune suppression, thymus involution, hyperkeratosis, and carcinogenesis. Here, we show physical interaction and mutual functional repression between AhR and NF-kappaB. This mutual repression may provide an underlying mechanism for many hitherto poorly understood PAH-induced toxic responses, and may also provide a mechanistic explanation for alteration of xenobiotic metabolism by cytokines and compounds that regulate NF-kappaB.

Combined carotid endarterectomy and coronary artery bypass: immediate and long-term results

Data from 213 cases of simultaneous carotid endarterectomy and coronary artery bypass grafting (CEN/CABG) were analyzed (1980-1996). There were 154 males (72.3%), and 59 females (27.7%), (mean age: 65. 6 years, range: 42-83). One hundred and thirty-two patients (62.0%) had angina, 58 (37.2%) had myocardial infarction, and 23 (10.8%) had congestive heart failure. Symptomatic cerebrovascular disease was present in 89 patients (41.7%). One hundred and twenty-two patients (57.2%) had three-vessel coronary artery disease, 41 (19.2%) had left main disease, and 27 (12.6%) had a low ejection fraction (ejection fraction </=30%). Significant (>/=75% diameter reduction) stenosis was present in 168 (78.8%) of the operated carotid arteries. The contralateral internal carotid artery was severely stenosed or occluded in 35 patients (16.4%). The hospital mortality rate was 5. 6% (12 patients). The cause of death was cardiac in ten patients (4. 6%), and neurologic in two (1%). Eleven patients (5.1%) developed a stroke postoperatively; eight strokes were ipsilateral to the operated artery, and six were permanent. Myocardial infarction occurred in five patients (2.3%). Independent predictors of early mortality were age >62 years, hypertension, and postoperative stroke (p < 0.05). Male sex was the only independent predictor of neurologic morbidity (p < 0.05). Late follow-up data were obtained for 163 (81.0%) patients (mean: 54.8 months, range: 1-168). Four (9. 3%) out of the 43 late deaths were attributed to strokes. There were three (1.8%) late ipsilateral strokes, and five (3.1%) contralateral strokes. The 5- and 10-year survival probabilities were 75 +/- 4%, and 52 +/- 6.9%. The freedom from late ipsilateral neurologic morbidity at 5 and 10 years were 97 +/- 1.7% and 90 +/- 4.0%, respectively. Taken together, the results indicate that combined carotid endarterectomy and coronary artery bypass grafting can be performed safely in this high-risk group of patients. Excellent long-term freedom from stroke can be expected.

Transcriptional suppression of estrogen receptor gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

TCDD, the most potent congener of the polychlorinated dioxins, has been shown to be an antiestrogen. The mechanisms of TCDD-induced antiestrogenicity are still under investigation. In this study, we investigated the effects of TCDD on the expression of the estrogen receptor (ER) gene. We studied the levels of un-spliced ER transcript (hnRNA) as well as the ER mRNA in ovary, uterus and liver of TCDD-treated mice with different genetic backgrounds. To quantitate the ER hnRNA levels, the intron and exon boundary of ER hnRNA was amplified by competitive RT-PCR. The ER mRNA from these mice was quantitated by competitive RT-PCR amplifying exons separated by an intron. ER hnRNA and ER mRNA levels were quantitated 4 days after a single i.p. dose of TCDD (5 microg/kg) in female C57BL/6J (B6) mice, which carry the responsive allele to TCDD. TCDD treatment significantly (p < 0.05) suppressed the levels of ER hnRNA in the ovary (27.4%) and uterus (21.9%). The decreases in ER hnRNA were coordinated with significant (p < 0.01) decreases in ER mRNA in ovary (57.7%) and uterus (37.6%). There was a significant decrease (20.3%, p < 0.05) in liver ER mRNA, however, the changes of ER hnRNA in liver were not significant. The coordinated decreases in ER hnRNA and mRNA in TCDD-treated mice suggest a suppression of transcription of the ER gene. We performed the same study on DBA/2J (D2) mice, which possess the "non-responsive" allele of the aryl hydrocarbon receptor (AhR). These mice demonstrated no significant decrease in either the ER mRNA or hnRNA after TCDD treatment. Overall, these results suggest that TCDD suppresses the gene expression of the ER receptor by decreasing its transcription, and the AhR plays an important role in mediating this response.

Epidemiological survey on clonorchiasis sinensis in Yangxin County of Hubei Province of PR China

An epidemiological survey of clonorchiasis was conducted at Panqiao township of Yangxin County of Hubei Province from June to November, 1993. The positive rate of cercaria in the body of intermediate hosts, Parafossarulus stratulus and Alocinma longicornis was 12.25% and 3.84% respectively. Positive rates of metacercariae in the bodies of Pseudonaphona parva was 48.15%, Ctenopharyngodon idellus 17.24% and Hypophthalmichthys nobilis 18.18%. Positive rate of eggs in the feces of cats was 36.36% and pigs 16.67%. It has been confirmed that there is a natural focus of clonorchiasis sinensis at Yangxin County of Hubei Province. A total population of 6,865 in 20 sites of 10 production brigades of Panqiao township was surveyed for infection with Clonorchis sinensis. The average infection rate in the local residents was 5.80%. Male had a higher infection rate than female. The infected persons were mainly peasants and school girls and boys. Most of the infected persons had light infections (I0) without a serious clinical manifestations.

Cyclic peptides as probes of the substrate binding site of the cytosolic tyrosine kinase, pp60c-src

A series of 48 cyclic peptides based on the amino acid sequence surrounding the autophosphorylation site of pp60(c-src) was synthesized and each was tested as both a substrate and an inhibitor of this protein tyrosine kinase. Starting with cyclo(Asp1-Asn2-Gln3-Tyr4-Ala5-Ala6-Arg7-Gln8-d- Phe9-Pro10) a six-amino-acid survey was performed at positions 1 through 8 to determine which positions were critical for affinity and phosphorylation and which amino acids produced the greatest activity. Our survey found that Arg7 was detrimental for binding and phosphorylation and that aromatic residues were preferred at this position. Further increases in affinity were obtained with hydrophobic residues at position 6 with the optimum for both affinity and phosphorylation being Phe. Changes on the "amino-terminal" side of Tyr4 resulted in reduced Vmax values, illustrating the requirement for acidic residues in peptidic tyrosine kinase substrates. The result of the survey was cyclo(Asp1-Asn2-Gln3-Tyr4-Ala5-Phe6-Phe7-Gln8-d-Phe 9-Pro10). The change of residues 6 and 7 resulted in a 42-fold increase in affinity and no increase in Vmax. As a substrate, this peptide displayed Michaelis-Menten kinetics at saturating ATP conditions. As an inhibitor, mixed inhibition was observed. A linear version of this peptide was 13-fold less potent an inhibitor than the cyclic peptide.

MediAgent: a WWW-based scalable and self-learning medical search engine

Searching for medical information on the Internet can be tedious and frustrating due to the number of irrelevant entries returned from generic search engines. We have developed MediAgent, a scalable search engine that aims to deliver a web-based medical search solution which is focused, exhaustive and able to keep improving its databases. The software package can run off a single low-end system and be scaled into a client-server, distributed computing architecture for high-end needs. This scalable architecture boosts MediAgent's handling capacity to tens of millions of web pages. In addition to large volume handling, MediAgent is designed to be manageable. All subsystems are not only highly configurable, but also support remote, interactive management and monitoring by the system administrator.

Csk phosphorylation and inactivation in vitro by the cAMP-dependent protein kinase

Csk is a protein tyrosine kinase that phosphorylates other protein tyrosine kinases of the Src family and down-regulates their activities. It is not known how Csk is regulated. We investigated the possibility that Csk is regulated through phosphorylation by examining if Csk can serve as an in vitro substrate for a panel of protein kinases. We found that Csk was phosphorylated by the cAMP-dependent protein kinase (PKA), but not by protein kinase C, Src, or the fibroblast growth factor receptor kinase. Csk phosphorylation in vitro by PKA is on a serine residue(s) and can reach a stoichiometry of approximately 0.6 mol phosphate per mole of enzyme. Furthermore, incubation with PKA in the presence of ATP and magnesium ion results in a time-dependent decrease in Csk kinase activity. A six-fold decrease in Csk activity (expressed as Vmax/Km ratio) was achieved due to a threefold increase in its Km and a twofold decrease in its Vmax value within 1 h of incubation with the catalytic subunit of PKA and ATP-Mg. Both phosphorylation and inactivation by PKA were blocked by a PKA-specific inhibitor. Csk mutants with a deleted SH2 or SH3 domain retained their ability to be phosphorylated and inactivated by PKA, indicating that the phosphorylation site is located within the catalytic domain. These studies suggest that the cAMP-dependent protein kinase can regulate Csk activity.

The C-terminal Src kinase (Csk) is widely expressed, active in HT-29 cells that contain activated Src, and its expression is downregulated in butyrate-treated SW620 cells

Csk expression was examined in human glioma, breast and colon cell lines, along with murine tissues. Relative to colon and glioma cell lines, Csk expression was highest in the breast cell lines. Relative to brain tissue, expression was 100-fold higher in the heart, kidney, liver, lung and spleen. Subcellular fractionation and cellular immunostaining indicated that it was localized in the cytosolic fraction. The expression of Csk was downregulated upon chemical-induced differentiation of SW620 human colon cells by treatment with sodium butyrate. Its expression localization and activity relative to Src are discussed.