Maintenance Treatment for Metastatic Pancreatic Cancer: Balancing Therapeutic Intensity with Tolerable Toxicity

Metastatic pancreatic ductal adenocarcinoma is typically treated with multi-agent chemotherapy until disease progression or intolerable cumulative toxicity. For patients whose disease shows ongoing control or response beyond a certain timeframe (≥3-4 months), options include pausing chemotherapy with close monitoring or de-escalating to maintenance therapy with the goal of prolonging progression-free and overall survival while preserving quality of life. There is currently no universally accepted standard of care and a relative dearth of randomized clinical trials in the maintenance setting. Conceptually, such therapy can entail continuing the least toxic components of a first-line regimen and/or introducing novel agent(s) such as the poly(ADP-ribose) polymerase inhibitor olaparib, which is presently the only approved drug for maintenance treatment and is limited to a genetically defined subset of patients. In addition to identifying new therapeutic candidates and combinations in the maintenance setting, including targeted agents and immunotherapies, future research should focus on better understanding this unique biologic niche and how treatment in the maintenance setting may be distinct from resistant/refractory disease; identifying molecular predictors for more effective pairing of specific treatments with patients most likely to benefit; and establishing patient-reported outcomes in clinical trials to ensure accurate capture of quality of life metrics.

The Additional Diagnostic Benefit of Pancreatic Cancer Molecular Profiling After Germline Testing

OBJECTIVES

Germline genetic testing is universally recommended for patients with pancreatic cancer to guide therapeutic selection, but tumor molecular profiling (TMP) is not. We aimed to determine the real-world additional diagnostic benefit of TMP after germline testing for detecting therapeutically actionable alterations.

METHODS

Medical records and genetic test reports were reviewed for all patients who underwent germline testing and TMP at the University of California San Francisco during January 2016-January 2020. The detection rate of actionable alterations with germline testing alone was compared to that with both germline testing and TMP.

RESULTS

Among 738 eligible patients, 144 (20%) met study criteria. Germline testing detected 10 actionable alterations in 10 patients. Tumor molecular profiling identified 3 new therapeutic targets among these 10 patients and 45 targets in 41 additional patients, increasing the number of patients with actionable findings from 10 (7%) to 51 (35%). Most actionable alterations (35/58, 60%) involved genes associated with the Homologous Recombination DNA Damage Repair pathway.

CONCLUSIONS

Tumor molecular profiling after germline testing increased the detection of actionable alterations by 5-fold. Tumor molecular profiling is a necessary complement to germline genetic testing to fully inform therapeutic decision making for all patients with pancreatic cancer.

Implementation of an Embedded In-Clinic Genetic Testing Station to Optimize Germline Testing for Patients with Pancreatic Adenocarcinoma

BACKGROUND

Germline genetic testing is universally recommended for patients with pancreatic cancer, but testing remains infrequent. In May 2018, we implemented a systematic patient intake workflow featuring an in-clinic genetic testing station (GTS) at the University of California San Francisco (UCSF) to expedite genetic counseling and facilitate sample collection. We sought to determine the impact of this innovation on rates of genetic counseling and testing.

METHODS

Medical records, patient intake records, and genetic test reports were retrospectively reviewed for new patients with pancreatic cancer eligible for germline testing at UCSF from May 2018 to May 2019. Primary outcomes included the rate of offered genetic counseling and confirmed germline testing. Data were compared for periods before and after GTS implementation. Associations between demographic characteristics and testing rates were assessed.

RESULTS

Genetic counseling/testing was offered to 209 (94%) of 223 eligible patients, and 158 (71%) completed testing (135 at UCSF, 23 elsewhere). Compared with a traditional referral-based genetic counseling model, confirmed testing increased from 19% to 71%, patient attrition between referral and genetics appointment decreased from 36% to 3%, and rate of pathogenic variant detection increased from 20% to 33%. Patients who were younger, identified as non-Hispanic White, and spoke English as a primary language were more likely to complete testing.

CONCLUSIONS

Implementation of a systematic patient intake workflow and in-clinic GTS resulted in the highest reported real-world rate of germline testing for patients with pancreatic cancer. Health care disparities were identified and will guide future innovation. This report provides a model for other centers to create a similar testing infrastructure.

IMPLICATIONS FOR PRACTICE

This study demonstrates that a systematic patient intake workflow and associated in-clinic genetic testing station improve delivery of genetic counseling and completion of germline testing for patients with pancreatic cancer. This study achieved, to the authors' knowledge, the highest real-world rate of confirmed genetic testing in this patient population. This article describes this innovation in detail to guide replication at other medical centers and facilitate guideline-concordant care for patients with pancreatic cancer. This infrastructure can also be applied to other cancers for which germline testing is recommended.

Durable response after immune checkpoint inhibitor-related diabetes in mismatch repair deficient pancreatic cancer

Mismatch repair protein deficiency occurs in 0.8-2% of pancreatic ductal adenocarcinomas and confers susceptibility to immunotherapy. Herein, we report the case of a patient with Lynch syndrome-associated, locally advanced mismatch repair protein deficiency pancreatic ductal adenocarcinomas who demonstrated a sustained response to second-line treatment with pembrolizumab, but eventually developed immune-related diabetic ketoacidosis requiring discontinuation of treatment. He has since remained in remission, off treatment, over the following 3 years, with regular surveillance showing no clinical or radiographic evidence of disease progression. The patient's unusual disease course raises the question of whether this serious immune-related adverse event affecting the organ of malignant involvement may have predicted his remarkable and durable response.

Anxious, Depressed, and Planning for the Future: Advance Care Planning in Diverse Older Adults

OBJECTIVES

To determine whether depression and anxiety are associated with advance care planning (ACP) engagement or values concerning future medical care.

DESIGN

Cross-sectional.

PARTICIPANTS

English- and Spanish-speaking patients, aged 55 years and older, from a San Francisco, CA, county hospital.

MEASURES

Depression was measured by the Patient Health Questionnaire 8-item scale, and anxiety was measured by the Generalized Anxiety Disorder 7-item scale, using standardized cutoffs of 10 or more for moderate-to-severe symptoms. ACP engagement was measured using validated surveys of ACP behavior change (e.g., self-efficacy and readiness; mean five-point Likert score) and ACP actions (e.g., ask, discuss, and document wishes; 0- to 25-point scale), with higher scores representing higher engagement. In addition, we asked a question about valuing life extension ("some health situations would make life not worth living"). We used adjusted linear and logistic regression.

RESULTS

Mean age of 986 participants was 63 years, 81% were non-White, 39% had limited health literacy, 45% were Spanish speaking, 13% had depression, and 10% had anxiety. After adjustment for demographic and health status variables, participants who were depressed versus not depressed had higher ACP behavior change scores (0.2 points; 95% confidence interval (CI) = 0.06-0.38; P = .007), higher ACP action scores (1.5 points; 95% CI = 0.51-2.57; P = .003), and higher odds of not valuing life extension (odds ratio (OR) = 2.5; 95% CI = 1.5-4.3; P < .001). Results were similar in participants with versus without anxiety (ACP behavior change: 0.2 points; 95% CI = 0.05-0.40; P = .01; ACP action scores: 1.2 points; 95% CI = 0.14-2.32; P = .028; odds of not valuing life extension: OR = 2.3; 95% CI = 1.3-3.9; P = .004).

CONCLUSION

Depression and anxiety were associated with greater ACP engagement and not valuing life extension. Although the direction of association between ACP engagement and values with anxiety and depression cannot be determined in this cross-sectional study, these conditions may influence ACP preferences. Future studies should assess whether changes in anxiety or depression affect ACP preferences over time.

Postoperative Exacerbation of Oxaliplatin-induced Neurotoxicity in Gastrointestinal Cancers: A Case Series

BACKGROUND/AIM

Oxaliplatin-induced neurotoxicity (OIN) can be severe and dose-limiting with clinically significant symptoms that persist for years. Few published reports have described postoperative exacerbation of OIN and more longitudinal data are needed to better characterize the phenomenon.

PATIENTS AND METHODS

We identified 13 patients diagnosed with colon (n=7), rectal (n=4) or pancreatic (n=2) cancer who experienced postoperative OIN exacerbation at our medical center. Charts were reviewed for demographic and clinical data regarding OIN.

RESULTS

OIN exacerbation was documented 0.5-7.0 months after the first surgery following oxaliplatin exposure, with a median duration of 10.6 months (range=1.4-86.1 months). OIN exacerbation persisted in 3/13 patients at last follow-up, and improved to pre-operative levels in 6/13 patients (with complete resolution in 4/13) within a median of 3.6 months from initial exacerbation.

CONCLUSION

Given the widespread use of oxaliplatin in neoadjuvant and first-line treatment for gastrointestinal cancers, further study is warranted to prospectively and systematically define risks for postoperative OIN exacerbation.

Referral frequency, attrition rate, and outcomes of germline testing in patients with pancreatic adenocarcinoma

Hereditary predisposition is estimated to account for 10% of all pancreatic cancer cases. However, referral patterns and clinical workflow for germline testing in this disease differ significantly by institution, and many at-risk patients may not undergo appropriate counseling and testing. We undertook an analysis of patients diagnosed with pancreatic cancer (PDAC) who were referred to the Clinical Genetics program of a high-volume academic center over a 3-year period to assess referral frequency, evaluate the yield of germline testing in this selected patient cohort, and elucidate the reasons individuals did not undergo recommended germline testing. Medical records of patients with PDAC referred for genetic counseling between January 2015 and October 2017 were reviewed for demographic, medical/family history, and disease-specific data. If testing did not occur, reasons were documented. Genetic test results were categorized as negative, variants of unknown significance, or established pathogenic mutations. Descriptive statistics included means with standard deviations; associations were analyzed with t test and Fisher's exact test. 32% (137 of 432) of PDAC patients were referred for genetic counseling, but only 64% attended their appointment and 60% ultimately underwent germline testing. Common reasons for attrition included worsening disease severity, lack of patient follow-up, insurance concerns, and logistic/travel challenges. Pathogenic germline mutations were detected in 20% (16 of 82) of patients tested, distributed across races/ethnicities, and significantly associated with younger age and positive family history of breast cancer. PDAC patients frequently do not undergo genetic counseling/germline testing despite appropriate referrals, highlighting a need to develop streamlined processes to engage more patients in testing, especially those with high-risk features.

Power outages and refrigerated medicines: The need for better guidelines, awareness and planning

WHAT IS KNOWN AND OBJECTIVE

Vaccines and other pharmaceuticals are essential medical supplies that require continuous storage at specific temperatures to maintain viability. Power outages can lead to a break in the cold chain, resulting in the degradation of essential medicines.

COMMENT

After a power outage, the stability of vaccines and other medicines can be difficult to ascertain. Many public health guidelines therefore recommend discarding potentially compromised pharmaceuticals unless the cold chain can be guaranteed-a costly endeavour. There are government guidelines aimed at minimizing exposure to high temperatures in the event of a power outage; however, the usefulness of these guidelines is uncertain.

WHAT IS NEW AND CONCLUSION

The actual cost of vaccine and pharmaceutical loss due to a break in the cold chain is poorly studied and requires further research. Additional recommendations regarding the stability of specific medicines would also be a valuable resource.

A Phase I Study of FOLFIRINOX Plus IPI-926, a Hedgehog Pathway Inhibitor, for Advanced Pancreatic Adenocarcinoma

OBJECTIVES

In mouse models of pancreatic cancer, IPI-926, an oral Hedgehog inhibitor, increases chemotherapy delivery by depleting tumor-associated stroma. This multicenter phase Ib study evaluated IPI-926 in combination with FOLFIRINOX (5-fluorouracil, leucovorin, irinotecan, oxaliplatin) in patients with advanced pancreatic cancer.

METHODS

Patients were treated with once-daily IPI-926 plus FOLFIRINOX. A 3 + 3 dose escalation design was used, with cohort expansion at the maximum tolerated dose. A subset of patients underwent perfusion computed tomography to assess changes in tumor perfusion.

RESULTS

The maximum tolerated dose was identified 1 dose level below standard FOLFIRINOX. Common treatment-related adverse events included liver function test abnormalities, neuropathy, nausea/vomiting, and diarrhea. Objective response rate was high (67%), and patients receiving IPI-926 maintenance showed further declines in CA19-9 levels even after FOLFIRINOX discontinuation. Treatment did not result in consistent increases in tumor perfusion. The study closed early when a separate phase II trial of IPI-926 plus gemcitabine indicated detrimental effects of this combination.

CONCLUSIONS

This is the first study to demonstrate the feasibility of using FOLFIRINOX as the chemotherapeutic backbone in a clinical trial design. Although robust antitumor activity and acceptable safety were observed with the addition of IPI-926 to this regimen, future development of Hedgehog inhibitors in pancreatic cancer seems unlikely.

Statin use and risk of pancreatic cancer: results from a large, clinic-based case-control study

BACKGROUND

Statins are cholesterol-lowering medications with pleiotropic effects, including alterations in growth signaling, as well as immunomodulatory and anti-inflammatory effects that may alter cancer risk. Evidence from previous epidemiologic studies is inconsistent about whether statin use is associated with a reduced risk of pancreatic cancer (PC).

METHODS

Patients with confirmed diagnoses of PC (cases) were recruited from medical and surgical oncology clinics, with controls (frequency-matched by sex and age) recruited from general medicine clinics, at a high-volume academic medical center over a 6-year period (2006-2011). Direct interviews were conducted with an epidemiological risk factor questionnaire covering topics such as medical history, lifestyle factors, and medication usage. Adjusted multivariable logistic regression was used to compute odds ratios (ORs) and 95% confidence intervals (CIs) as estimates of the relative risk of PC.

RESULTS

Data were obtained from 536 cases and 869 controls. Ever use of statins was associated with a 34% reduced PC risk (OR, 0.66; 95% CI, 0.47-0.92). In sex-stratified analyses, risk was statistically significantly reduced in men only (OR for men, 0.50; 95% CI, 0.32-0.79; OR for women, 0.86; 95% CI, 0.52-1.43). Duration of use was inversely associated with PC risk (>10-year use: overall OR, 0.51; OR for men, 0.41; 95% CI, 0.21-0.80; P(trend)  = .006).

CONCLUSIONS

This is the largest case-control study to demonstrate an inverse association between statin use and PC risk. Risk reduction in statin users appears to be sex-specific and is more pronounced in long-term users. Further research is warranted to better characterize this association and clarify the roles of underlying biologic mechanisms.

A patient with cholangiocarcinoma demonstrating pathologic complete response to chemotherapy: exploring the role of neoadjuvant therapy in biliary tract cancer

The role of neoadjuvant chemotherapy and/or radiation for localized or potentially resectable cholangiocarcinoma (CCA) has not been well established. We present here the case of a patient with an extrahepatic CCA who achieved a pathologic complete response after undergoing preoperative gemcitabine-based chemotherapy, without sequential or concurrent use of radiation. Further evaluation of neoadjuvant strategies in CCA, including not only combined-modality therapy but also the use of chemotherapy exclusively, is warranted in prospective study design.

Abstract 2160: Metformin use is not associated with pancreatic cancer risk in a clinic-based case-control study conducted in the San Francisco Bay Area, California

Patients with pancreatic cancer (PC) are commonly diagnosed at advanced stages of the disease, at which point cure is no longer possible. A better understanding of risk or protective factors for PC may inform prevention and/or early detection strategies. Metformin, a commonly used drug for type II diabetes (DM2), has been shown in some observational clinical studies to reduce the risk of several cancer types, including PC. Its antineoplastic effects occur through inhibition of mammalian target of rapamycin (mTOR) and induction of cell cycle arrest and apoptosis, among other mechanisms. The current case-control study addresses two distinct research questions: whether metformin use is associated with PC risk among those with DM2, and whether metformin modulates the risk of PC associated with DM2.

We recruited 536 cases and 869 controls, predominantly from University of California, San Francisco (UCSF) medical and surgical oncology clinics (cases) and general medicine clinics (controls), over a six-year period (2006-2011). Controls were frequency-matched to cases by sex and age in 5-year groups. Case diagnoses were confirmed by patient medical record and cancer registry data. Direct interviews were conducted by trained interviewers using an epidemiological risk factor questionnaire. The association between metformin use and PC risk among diabetics was analyzed using propensity score-weighted unconditional logistic regression, whereas the effect of metformin use on the association between DM2 and PC in the total study population was analyzed using standard multivariable logistic models.

Metformin was the most common anti-diabetic drug used by DM2 study participants (66.5%). Among DM2 participants (N=170), ever use of metformin was not associated with PC risk in adjusted models (OR: 1.01, 95%CI: 0.61-1.68). Similarly, duration of metformin use was not statistically significantly associated with PC risk when also adjusted for DM2 duration. Among the total study population (N=1405), DM2 was not statistically significantly associated with PC risk (adjusted OR: 1.28, 95%CI: 0.81-2.00). However, risk was inversely associated with DM2 duration; participants whose DM2 was diagnosed 1-5 years prior to PC diagnosis/interview were at markedly increased risk (OR: 2.47, 95%CI: 1.25-4.85). Stratification of participants with DM2 by metformin use revealed no difference in risk between never (OR: 1.44, 95%CI: 0.78-2.67) and ever users (OR: 1.19, 95%CI: 0.72-1.99) relative to non-DM2 participants. PC risk also did not differ across groups of metformin or DM2 duration.

In this clinic-based case-control study of PC, metformin use was not associated with PC risk. Specifically, our results suggest that metformin is neither associated with PC risk in those with DM2, nor does it attenuate or exacerbate PC risk associated with DM2.

Citation Format: Evan J. Walker, Andrew H. Ko, Elizabeth A. Holly, Paige M. Bracci. Metformin use is not associated with pancreatic cancer risk in a clinic-based case-control study conducted in the San Francisco Bay Area, California. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2160. doi:10.1158/1538-7445.AM2014-2160

Metformin use among type 2 diabetics and risk of pancreatic cancer in a clinic-based case-control study

A better understanding of the association between diabetes and pancreatic cancer (PC) may inform prevention and/or early detection strategies. Metformin has been associated with reduced risk of certain cancers, including PC, in some observational clinical studies. We assessed whether metformin use was associated with PC risk among those with type 2 diabetes (DM2), and whether metformin use modulated the association between DM2 and risk of PC. In total, 536 PC cases and 869 frequency-matched controls were recruited predominantly from University of California San Francisco medical clinics from 2006 to 2011. Eligible participants completed direct interviews using a structured risk factor questionnaire. The association between metformin use and PC risk was assessed using propensity score-weighted unconditional logistic regression methods in analyses restricted to diabetics and adjusted multivariable logistic models in the total study population. Ever use of metformin was not associated with PC risk in analyses restricted to DM2 (N = 170) participants (adjusted OR: 1.01, 95% CI: 0.61-1.68). In the total study population (N = 1,405) using nondiabetics as the referent group, PC risk was inversely associated with diabetes duration (ptrend  < 0.001). Further, when DM2 participants were grouped by ever/never use of metformin and compared with nondiabetics, metformin use did not affect the association between DM2 and PC risk (never users: OR: 1.44, 95% CI: 0.78-2.67; ever users: OR: 1.19, 95% CI: 0.72-1.99). Results from our clinic-based case-control study suggest that metformin use is not associated with PC risk among those with DM2 and does not alter the association between DM2 and PC risk.

Hepatitis B viral reactivation secondary to imatinib treatment in a patient with gastrointestinal stromal tumor

Hepatitis B virus (HBV) reactivation is a known risk in cancer patients receiving cytotoxic or immunosuppressive therapy; however, the risk associated with newer molecularly-targeted agents has not been well-quantified. Imatinib, a small molecule inhibitor directed against BCR-ABL, CKIT, and other tyrosine kinases, has been associated with HBV reactivation primarily in patients treated for chronic myelogenous leukemia. Herein we present the first reported case of a patient who developed HBV reactivation while receiving imatinib therapy for a gastrointestinal stromal tumor (GIST) in the adjuvant setting. This eventually resulted in fulminant liver failure and was effectively treated with living-related donor liver transplant and anti-viral medication. Currently, no guidelines exist for HBV screening prior to imatinib therapy. This report emphasizes the need for such guidelines and supports the idea that viral reactivation is a risk in all imatinib-treated patients, regardless of the underlying disease.

Beyond first-line chemotherapy for advanced pancreatic cancer: an expanding array of therapeutic options?

While an increasing number of therapeutic options are now available for the first-line treatment of locally advanced or metastatic pancreatic cancer, the optimal choice for treatment in the second-line setting and beyond is less well defined. A variety of cytotoxic agents, either alone or in combination, have been evaluated, although primarily in the context of small single-arm or retrospective studies. Most regimens have been associated with median progression-free survival rates in the range of 2-4 mo and overall survival rates between 4-8 mo, highlighting the very poor prognosis of patients who are candidates for such treatment. Targeted therapies studied in this chemotherapy-refractory setting, meanwhile, have produced even worse efficacy results. In the current article, we review the clinical evidence for treatment of refractory disease, primarily in patients who have progressed on front-line gemcitabine-based chemotherapy. In the process, we highlight the limitations of the available data to date as well as some of the challenges in designing appropriate clinical trials in this salvage setting, including how to select an appropriate control arm given the absence of a well-established reference standard, and the importance of incorporating predictive biomarkers and quality of life measures whenever possible into study design.

Loss of the SxxSS motif in a human T-cell factor-4 isoform confers hypoxia resistance to liver cancer: an oncogenic switch in Wnt signaling

PURPOSE

Aberrantly activated Wnt/β-catenin signaling is important in hepatocellular carcinoma (HCC) development. Downstream gene expressions involving the Wnt/β-catenin cascade occur through T-cell factor (TCF) proteins. Here, we show the oncogenic potential of human TCF-4 isoforms based on the expression of a single conserved SxxSS motif.

METHODS

We investigated the TCF-4J and K isoform pair characterized by the presence (K) or absence (J) of the SxxSS motif. The mRNA expression profiles were examined in 47 pairs of human HCCs and adjacent non-cancerous liver tissues by RT-PCR. Proliferation, sphere assays and immunoblot analysis were performed under normoxia and hypoxia conditions. The ability of HCC cells overexpressing TCF-4J (J cells) and K (K cells) to grow as solid tumors in nude mice was explored.

RESULTS

TCF-4J expression was significantly upregulated in HCC tumors compared to corresponding peritumor and normal liver and was preferentially expressed in poorly differentiated HCCs. In contrast, TCF-4K was downregulated in those same HCC tumors. TCF-4J-overexpressing HCC cells (J cells) revealed a survival advantage under hypoxic conditions, high proliferation rate and formation of aggregates/spheres compared to overexpression of TCF-4K (K cells). The hypoxic J cells had high expression levels of HIF-2α and EGFR as possible mechanisms to promote tumorigenesis. Increased stability of HIF-2α under hypoxia in J cells was associated with a decreased level of von Hippel-Lindau (VHL) protein, a known E3 ligase for HIF-αs. In a xenograft model, the J cells rapidly developed tumors compared to K cells. Tumor tissues derived from J cells exhibited high expression levels of HIF-2α and EGFR compared to the slow developing and small K cell derived tumors.

CONCLUSIONS

Our results suggest that the specific TCF-4J isoform, which lacks a regulatory SxxSS motif, has robust tumor-initiating potential under hypoxic conditions.

Role of Raf Kinase Inhibitor Protein in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) accounts for 80-90% of primary liver tumors and is one of the most common and devastating malignant diseases worldwide. The MAPK signaling pathway is activated in over 90% of HCCs, and RKIP has been identified as an inhibitor of the MAPK pathway. It has been observed that downregulation of RKIP expression in HCC tumors contributes to constitutive activation of the ERK/MAPK pathway and promotes proliferation and migration of HCC cells. More important, activation of IGF-I/ERK/MAPK pathways can be blocked by restoration of RKIP levels. The protein levels of RKIP are significantly reduced in HCC, whereas mRNA levels only decreased in 41% of HCC samples studied, suggesting that the downregulation of RKIP in HCC may be influenced through multiple mechanisms both at the mRNA and protein levels. In this context, mTOR inhibitor, insulin, and proteasome inhibitors were found to modulate RKIP expression in FOCUS HCC cells. A better understating of mechanisms by which RKIP expression is downregulated in HCC may be critical to develop a possible target for therapeutic intervention of HCC.

Abstract 4067: A T-cell factor-4 motif regulates the phenotype of hepatocellular carcinoma cells

T-cell factor (TCF) family proteins play a crucial role in regulating the activation of Wnt/β-catenin responsive target genes. Among the family proteins, TCF-4 is predominantly expressed in human HCC tissues. We have recently cloned 14 TCF-4 isoforms from human hepatoma cell lines, and naming them in alphabetical order from A to M. A TCF-4J and K pair has been identified based on the presence (K) or absence (J) of the SxxSS motif at the beginning of exon 9. This motif may modulate transcriptional activity of TCF-4 through phosphorylation/dephosphorylation of serine residues (Pukrop et al., Cancer Res 2001). However, cell-based functional analysis of this motif has yet to be performed. The AIM of this study was to investigate whether TCF-4J and K have distinct cellular phenotypes due to SxxSS motif expression. Methods: The human hepatoma cell line Huh-7 was used in this study. The cells were transfected with TCF-4J and K expression plasmids, and protein levels in cell lysates and nuclear extracts were examined by Western blot analysis. TCF-4K mutants with substitution of serine (S) to alanine (A) were generated by site-directed mutagenesis. Results: Protein expression of all cloned TCF-4 isoforms was confirmed by Western blot analysis. Expression levels of cyclin D1, which is a direct target of TCF-4, was increased in both cell lysates and the nuclear extracts of the TCF-4K, but not in TCF-4J-transfected cells. The TCF-4K isoform with a S269A mutation revealed a decrease in the expression level of cyclin D1, while the mutant with either a S272A or S273A substitution did not, which suggests that phosphorylation of serine 269 was critical to up-regulating cyclin D1 gene expression. Conclusion: The findings from functional analysis following mutagenesis of the SxxSS motif suggest that serine phosphorylation of this motif resulted in the altered target genes expression, including cyclin D1. Therefore, TCF-4 isoforms regulate the phenotype of HCC cells.

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 4067.

Low density contrast agents for x-ray phase contrast imaging: the use of ambient air for x-ray angiography of excised murine liver tissue

We report a new preparative method for providing contrast through reduction in electron density that is uniquely suited for propagation-based differential x-ray phase contrast imaging. The method, which results in an air or fluid filled vasculature, makes possible visualization of the smallest microvessels, roughly down to 15 microm, in an excised murine liver, while preserving the tissue for subsequent histological workup. We show the utility of spatial frequency filtering for increasing the visibility of minute features characteristic of phase contrast imaging, and the capability of tomographic reconstruction to reveal microvessel structure and three-dimensional visualization of the sample. The effect of water evaporation from livers during x-ray imaging on the visibility of blood vessels is delineated. The deformed vascular tree in a cancerous murine liver is imaged.

Cytokine-activated endothelium recruits osteoclast precursors

Osteoclast precursors reach sites of osteoclast formation and remodelling via the vasculature and are therefore destined to encounter endothelium before migrating to the bone surface. Here we investigated the hypothesis that endothelium may be involved in the regulation of osteoclast precursor recruitment to sites of bone resorption. Osteoclast precursors in human peripheral blood were identified by their ability to form mature osteoclasts in 21-day cultures supplemented with RANKLigand, M-CSF, 1,25(OH)(2)-vitamin D(3), dexamethasone and prostaglandin E(2). Under control conditions few osteoclast precursors adhered to endothelial cells (the human bone marrow-derived endothelial cell line BMEC-1). However, BMEC-1 cells treated with the resorption stimulating cytokines IL-1beta and TNFalpha depleted the PBMC population of all osteoclast precursors. These results provide the first evidence that osteoclast precursors can adhere to endothelium and suggest that endothelium could play an important role in the recruitment of osteoclast precursors to sites of bone resorption.

Polydermatomyositis with anti-PL7 antibody: clinical and laboratory follow-up over a five year period

Anti-PL7 antibodies to threonyl-tRNA synthetase purified from beef liver were observed in the serum of a dermatopolymyositis patient. They were identified by CIE and DID using a standard anti-PL7 antiserum and quantified by ELISA in serum samples taken over a five year period. The level of antibodies against not only threonyl-tRNA synthetase but also several muscle proteins including tropomyosin, was strongly correlated with disease activity and treatment. This correlation may prove important both in monitoring the response of the patient to treatment and to our understanding of the aetiology of the disease.

Sequence homology between encephalomyocarditis virus protein VPI and histidyl-tRNA synthetase supports a hypothesis of molecular mimicry in polymyositis

The amino acid sequence of histidyl-tRNA synthetase, the Jo-I antigen of polymyositis, has been compared with that of the polyprotein of encephalomyocarditis virus (EMCV), an agent shown recently to produce polymyositis symptoms in mice. It is shown that there is significant sequence homology between a region of the synthetase formerly identified by us as a possible epitope and a region on the coat protein VPI of EMCV. The viral protein also shows significant sequence homology with several muscle proteins. Identification of the likely spatial location of the VPI sequence on the shell of the virus by comparison with two other picornaviruses whose three dimensional structures have been determined, reveals it to be homologous with known immunogenic sites on these viruses. Independent structural localisation of the possible epitope by comparison with two aminoacyl-tRNA synthetases, whose three dimensional structures are known, also reveals that the sequence in question is likely to be favourably placed on histidyl-tRNA synthetase to crossreact with appropriate antibodies. These findings provide more definitive evidence in support of our previous suggestion that molecular mimicry could explain the origin of serum antibodies to aminoacyl-tRNA synthetases in polymyositis and suggests a likely viral etiology for the disease.

Purification of bovine liver histidyl-tRNA synthetase, the Jo-1 antigen of polymyositis: size of the whole enzyme and its characteristic proteolytic fragments

We have recently reported the marked increase in frequency which can be achieved in the detection of the anti-Jo-1 antibody of polymyositis in serum samples by replacing commercial mixtures of cytoplasmic and nuclear antigens with the purified antigen, histidyl-tRNA synthetase. The present paper describes a method for purifying this antigen and an investigation of its size. Molecular masses previously reported for the enzyme have varied from 85-154 kDa and subunit molecular masses varying from 40-77 kDa have been observed. Several of these fragments are of sizes similar to those of a number of other autoantigens commonly observed in connective tissue diseases. Since the clinical identification of these autoantigens often relies exclusively on size determination by Western blotting, we have characterized the commonly occurring fragments of histidyl-tRNA synthetase lest they confuse such identification. It is concluded that histidyl-tRNA synthetase, like many other aminoacyl-tRNA synthetases, is subject to severe proteolysis during extraction procedures. Several characteristic fragments (Mr = 80, 75, 61, 55, 50 and 45 kDa) result, a finding that provides a satisfactory explanation of the various values previously reported. The intact bovine enzyme is a dimer of molecular mass close to 160 kDa.

Improved detection of anti-Jo-1 antibody, a marker for myositis, using purified histidyl-tRNA synthetase

The increased detection of anti-Jo-1 antibody afforded by the use of the purified antigen, histidyl-tRNA synthetase, in counterimmunoelectrophoresis is demonstrated. Using purified antigen, anti-Jo-1 antibody was detected in the sera of 16/33 (48.5%) patients with confirmed myositis and in 20/45 (44.5%) patients with confirmed or possible myositis. This rate is approximately double that obtained with commercial thymus extracts both in this study and seven others reported in the literature. The presence of antibody shows marked correlation with the activity of myositis at the time of serum sampling and with the presence of interstitial lung disease. Detection rates are similar in patients with polymyositis and dermatomyositis both with and without additional connective tissue diseases.

Polymyositis and molecular mimicry, a mechanism of autoimmunity

The amino acid sequences of Escherichia coli histidyl-tRNA synthetase and alanyl-tRNA synthetase, two proteins recently identified as autoantigens in polymyositis, were compared by a computer alignment procedure with those of the 3600 proteins tabulated in the National Biomedical Research Foundation protein sequence database. Both proteins contain sequences long enough to function as epitopes that match sequences on viral and muscle proteins. The homology thus revealed not only lends strong support to mechanisms of autoimmunity that invoke the theory of molecular mimicry of viral proteins, but also suggests a rationale for the skeletal muscle target of polymyositis.

Characterization of digoxin binding and daunorubicin uptake by isolated mature rat cardiac myocytes

Myocytes isolated from ventricular muscle of mature rat heart have been used for characterization of digoxin binding and to establish whether a relationship exists between digoxin binding and uptake of daunorubicin. High- and low-affinity digoxin binding sites have been identified; respectively, 0.9 +/- 0.1 X 10(7) sites/myocyte, Kd 70-77 nM and 7 +/- 2 X 10(7) sites/myocyte, Kd 1.4-1.7 microM. Myocytes accumulate daunorubicin to an intracellular concentration 30-40 times that in the medium. We find no evidence that saturation of digoxin binding sites alters daunorubicin uptake or that daunorubicin influences binding of digoxin. Alteration of sarcolemmal membrane properties is demonstrated by inhibition of amino acid transport reflected in protein synthesis rates. Calmodulin activation of phosphodiesterase appears insensitive to daunorubicin.

Molecular weights of mitochondrial and cytoplasmic aminoacyl-tRNA synthetases of beef liver and their complexes

In eukaryotes, multienzyme complexes containing five to nine aminoacyl-tRNA synthetase activities have frequently been reported. In this study, we report the existence, in bovine liver cytoplasm, of a multienzyme complex containing at least 16 activities which can be disrupted by homogenization to give rise to smaller complexes and noncomplexed synthetases. Determination of the size and component activity of these complexes and of the molecular weights of all 20 free synthetases suggests that the smaller complexes and free activities normally identified arise from the larger complex by well-defined stages during homogenization. We also show that similar, though not identical, complexes are found in bovine liver mitochondria and give the molecular weights of 16 mitochondrial synthetases.

Amino acid transport and protein synthesis in energetically-stable calcium-tolerant isolated cardiac myocytes

Myocytes isolated by enzymic dispersion from adult rat ventricular tissue are shown to be energetically stable in the presence of 0.5 mM CaCl2. ATP and ADP content and rates of lactate production are comparable with those of intact myocardial tissue and consistent with these cells being tightly coupled. Addition of 2,4-dinitrophenol precipitates rapid changes in adenine nucleotide concentrations and a 10-fold increase in lactate production. Cardiac myocytes selectively transport neutral amino acids of the A and L classes. Transport of the amino acid analogue alpha-aminoisobutyric acid is an active, temperature-dependent and insulin-sensitive process. The apparent Km for alpha-aminoisobutyric acid transport is similar to that determined for embryonic cardiac cells. Mature myocytes incorporate labelled amino acids into cytoplasmic proteins with molecular weights ranging from 10 000 to 150 000. Newly synthesised protein is metabolically stable. The data establishes calcium-tolerant myocytes as an experimental system offering many advantages over whole hearts for short- and long-term studies of protein synthesis and catabolism.

Defaecation frequencies in Black, Indian, Coloured and White populations - what do they signify?

Using questionnaires covering a 7-day period, frequencies of defaecation were determined in a total of 2937 Black, Indian. Coloured and White subjects aged from 10 years upwards. It transpired that the overall frequency in rural Blacks was roughly twice that of Whites. Among rural Blacks defaecation frequencies of 5-7 per week were recorded in 16%, and from 1-3 per day in 80%. The corresponding figures among urban Blacks were 25% and 71%, among Indians 58% and 34%, among Coloureds 46% and 39%, and among Whites 59% and 29%. The wide differential in frequencies between Blacks and Whites is consistent with the wide differential prevailing in proneness to noninfective bowel diseases. On the other hand, Indians and Coloureds had defaecation frequencies little different on average from those of Whites, yet the former two populations are far less prone to bowel diseases. Hence caution must be exercised in correlating defaecation frequency with proneness to bowel diseases. Since bowel behaviour includes numerous aspects, defaecation frequency should not be regarded in isolation.

Location and properties of two isoenzymes of cardiac adenylate kinase

Adenylate kinase catalyses the equilibrium 2ADP = ATP + AMP. There are two isoenzymes of adenylate kinase in bovine ventricular tissue, one cytoplasmic, the other mitochondrial. Mitochondrial subfractionation locates this isoenzyme between the mitochondrial membranes with fatty acid-CoA ligase. The cytoplasmic and mitochondrial isoenzymes are distributed in ratio 3:2, and both forms were purified to homogeneity. They differ principally by charge, Km values for ATP, ADP and AMP, pH-stability and -activity profiles, and susceptibility to the inhibitor adenosine pentaphosphoadenosine. The forward and reverse reactions show similar energies of activation for the cytoplasmic enzyme, but differ for the mitochondrial enzyme. The molecular weights are indistinguishable. An integrated mechanism is formulated whereby one isoenzyme suppresses the activation of fatty acid and the other enhances carbohydrate utilization in hypoxic myocytes.

Field study of coccidial and rotaviral diarrhoea in unweaned piglets

A study of diarrhoea in unweaned piglets was carried out in nine herds, with special reference to the enteropathogenic agents which could be demonstrated. Coccidial (Isospora suis) and rotaviral infections were both identified, either singly or in combination. More extensive studies of I suis infection were undertaken in two of the herds and it was found that diarrhoea occurred most commonly in five- to 14-day-old piglets. Piglets with I suis infection were not necessarily diarrhoeic but grew poorly compared to uninfected piglets. I suis infection in litters correlated with oocyst excretion in sows. In herds with I suis infection, amprolium and monensin were used in the sow ration to achieve control, and in one herd oral dosing of piglets with amprolium in the first three or four days of life was carried out.

Preparation of allosteric ribonuclease

A method for the preparation of allosteric ribonuclease from bovine pancreas is described. The effects of freeze-drying ribonuclease from acid and alkaline solutions on plots of velocity versus substrate concentration for the hydrolysis of 2':3'-cyclic CMP are examined. Comparison of these plots with the plots obtained with severeal commercial enzyme preparations indicates that the conformation of the enzyme is dependent on the method of preparation. Aging experiments demonstrate that further conformational changes occur at different rates, depending on the methods of storage. Results suggest that the allosteric behaviour of ribonuclease has not always been observed with commercial preparations, owing to variations in methods of preparation and storage of the enzyme.

The nature of the allosteric interactions of ribonuclease and its ligands

The allosteric model for ribonuclease activity by Walker, Ralston & Darvey [(1975) Biochem.J. 147, 425--433; (1976) Biochem.J. 153, 329--337] involves the binding of a large number of molecules of substrate or substrate analogue to a series of allosteric sites on the enzyme. In the present paper, the nature of these allosteric interactions is investigated. The effects of ionic strength pH carbamoylation of lysine to homocitrulline and of deamidation of glutamine and asparagine on plots of velocity versus substrate concentration are examined and evidence is presented that the allosteric transition involves an electrostatic interaction between the negatively charged substrate molecules and the cationic groups on the enzyme.

A procedure for obtaining initial estimates of parameters appearing in steady-state rate or equilibrium binding equations

A "peeling" procedure is described for obtaining initial estimates of the parameters in the equation: formula: (see text), where P(x) and Q(x) are polynomials in x. The method is illustrated, in the context of enzyme kinetics, using data which are fitted to the following equation: formula: (see text), where v denotes the initial steady-state velocity at an initial substrate concentration S, and a1, a2, b1, and b2 are non-negative constants. The applicability and limitations of the method for data fitting in fields such as enzyme kinetics and ligand-binding studies are discussed.

Further evidence for an allosteric model for ribonuclease

Evidence is presented from three experimental systems to support the allosteric model of Walker et al. (1975) (Biochem. J. 147, 425-433) which explains the substrate-concentration-dependent transition observed in the RNAase (ribonuclease)-catalysed hydrolysis of 2':3'-cyclic CMP (cytidine 2':3'-cyclic monophosphate). 1. Kinetic studies of the initial rate of hydrolysis of 2':3'-cyclic CMP show that the midpoint of the transition shifts to lower concentrations of 2':3'-cyclic CMP in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, 3'-UMP and Pi; 2'-CMP and 2'-UMP do not cause such a shift. 2. Trypsin-digestion studies show that a conformational change in RNAase to a form less susceptible to tryptic inactivation is induced in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, and 3'-UMP. 2'-CMP, 2'-AMP and 2'-UMP do not induce this conformational change. 3. Equilibrium-dialysis experiments demonstrate the multiple binding of molecules of 3'-CMP, 3'-AMP and 5'-AMP to a molecule of RNAase. 2'-CMP binds the ratio 1:1 over the analogue concentration range studied.

An allosteric model for ribonuclease

Data from two assay systems show that the kinetics of the hydrolysis of cytidine 2':3'-cyclic monophosphate by bovine pancreatic RNAase (ribonuclease) is not consistent with conventional models. An allosteric model involving a substrate-dependent change in the equilibrium between two enzyme conformations is proposed. Such a model gives rise to a calculated curve of velocity versus substrate concentration which fits the experimental data. The model is also consistent with the results of an examination of the tryptic digestion of RNAase. Substrate analogues are able to protect RNAase against hydrolysis by trypsin and the percentage of RNAase activity which remains after digestion increases sigmoidally as the analogue concentration is increased. The model also explains the pattern seen in the Km values quoted in the literature and is consistent with strong physical evidence for a ligand-induced conformational change for RNAase reported in the literature.