The effect of non-oncology drugs on clinical and genomic risk in early luminal breast cancer

BACKGROUND

An effect of non-oncology medications on cancer outcome has been proposed. In this study, we aimed to systematically examine the impact of commonly prescribed non-oncology drugs on clinical risk and on the genomic risk [based on the Oncotype DX recurrence score (RS)] in early breast cancer (BC).

EXPERIMENTAL DESIGN

We collected data on clinical risk (stage and grade), genomic risk (Oncotype DX RS), and on non-oncology medications administered to 1423 patients with estrogen receptor-positive human epidermal growth factor receptor 2-negative BC during the month of their surgery. The influence of various medications on clinical and genomic risks was evaluated by statistical analysis.

RESULTS

Out of the multiple drugs we examined, levothyroxine was significantly associated with a high Oncotype DX RS (mean 24.78; P < 0.0001) and metformin with a low Oncotype DX RS (mean 14.87; P < 0.01) compared with patients not receiving other non-oncology drugs (mean 18.7). By contrast, there were no differences in the clinical risk between patients receiving metformin, levothyroxine, or no other non-oncology drugs. Notably, there was no association between the consumption of levothyroxine and metformin and proliferation marker (Ki67) levels, but both drugs were significantly associated with progesterone-related features, suggesting that they influence genomic risk through estrogen-dependent signaling.

CONCLUSIONS

The results of this study indicate a significant impact of metformin and levothyroxine on clinical decisions in luminal BC, with potential impact on the clinical course of these patients.

Real-life daily activity: the impact of misbeliefs on quality of life among cancer patients

Background

While side-effects and health-related quality of life (QoL) are routinely assessed in clinical trials, commonly used tools do not measure patients’ ability to maintain normal daily activities. QoL can be severely affected directly by the disease, the treatment side-effects and by personal and societal misconceptions promoting avoidance from activities perceived as dangerous for cancer patients. We examined practices of actively treated patients with cancer.

Methods

A questionnaire was designed, assessing daily activities (11 items) and dietary limitations (7 items) distributed between October and December 2019 (before the coronavirus pandemic) among patients treated at the Oncology Division of Tel Aviv Sourasky Medical Center.

Results

The study population comprised 208 patients who participated in the survey. The majority reported at least one social-environmental avoidance or dietary limitation (136, 65% and 120, 57.7%, respectively), including abstaining from social contact, avoiding pets, public domains, traveling and maintaining dietary constraints. Adoption of these measures was not associated with clinical, demographic factors and treatment type. The major sources guiding restrictions came from advice of non-medical personnel (55.7%), the Internet (7.2%) and personal choice by the patients themselves (24%).

Conclusions

Most cancer patients reported compromised daily activities, which are likely attributed to misbeliefs about disease and treatment, and have a deleterious impact on QoL, in its wider sense, namely, the ability to conduct a full and meaningful life. These findings call for the development and implementation of tools examining patients’ real-life activity, beyond side-effects or health-related QoL (HRQoL). We propose this assessment as an integral part in the evaluation of new drugs and technologies and as an additional endpoint in pivotal clinical trials.

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Side-effects and HRQoL routinely assessed in clinical trials do not fully measure patients’ maintenance of daily activities.

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We developed a questionnaire examining daily practices and implications of misbeliefs among actively treated cancer patients.

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Most patients reported compromised daily activities, affecting QoL in its wider sense: conducting a full and meaningful life.

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These findings call for the development and implementation of tools examining patients’ real-life activity, beyond HRQoL.

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We propose accounting for a more comprehensive assessment of QoL, and patient health care education dispelling misbeliefs.

The Role of Alpha-Klotho as a Universal Tumor Suppressor

The klotho gene is implicated in many physiological activities, among them aging, glucose metabolism, and phosphate and calcium metabolism. Many cellular activities of klotho were implicated in promoting these activities. Two of them, inhibition of the insulin-like growth factor-1 pathway and of the Wnt signaling pathway, are also major pathways associated with cancer development and progression. These discoveries prompted a surge of research aiming to elucidate the role of klotho in cancer. Studies show that klotho is universally silenced in a wide array of malignancies, including breast, pancreatic, ovarian, lung, colorectal, and melanoma, and that klotho's expression can serve as an invaluable prognostic marker. Epigenetic mechanisms, ie, promoter hypermethylation and histone deacetylation, are mainly associated with klotho's silencing; however, different micro-RNAs were also demonstrated to be involved in the process. The activity of klotho on cancer cells growth was also widely investigated, and accumulating data suggest that klotho forced expression or treatment with the soluble protein can inhibit cancer development and progression. Moreover, studies now aim to reveal the specific region in klotho protein that underlies this anticancer activity in order to develop efficient and safe klotho-based medications.

Klotho and the Growth Hormone/Insulin-Like Growth Factor 1 Axis: Novel Insights into Complex Interactions

The growth hormone (GH)/insulin-like growth factor (IGF)-1 axis is pivotal for many metabolic functions, including proper development and growth of bones, skeletal muscles, and adipose tissue. Defects in the axis' activity during childhood result in growth abnormalities, while increased secretion of GH from the pituitary results in acromegaly. In order to keep narrow physiologic concentration, GH and IGF-1 secretion and activity are tightly regulated by hypothalamic, pituitary, endocrine, paracrine, and autocrine factors. Klotho was first discovered as an aging-suppressor gene. Mice that do not express klotho die prematurely with multiple symptoms of aging, several of them are also characteristic of decreased GH/IGF-1 axis activity. Klotho is highly expressed in the brain, the kidney, and parathyroid and pituitary glands, but can also serve as a circulating hormone by its shedding, forming soluble klotho that can be detected in blood, cerebrospinal fluid, and urine. Several lines of evidence suggest an association between klotho levels and activity of the GH/IGF-1 axis: the GH-secreting cells in the anterior pituitary of klotho-deficient mice are hypotrophic; klotho levels are altered in subjects with pathologies of the GH/IGF-1 axis; and accumulating data indicate that klotho is a direct regulator of GH secretion. Thus, klotho seems to be a new player in the intricate regulation of the GH/IGF-1 axis.

The Effect of Klotho Treatment on Atherogenesis, Blood Pressure, and Metabolic Parameters in Experimental Rodent Models

Klotho is a transmembrane protein, expressed mainly in the kidneys and the choroid plexus. The extracellular domain of klotho is composed of 2 internal repeats, KL1 and KL2, which can be cleaved and act as hormones. Klotho-deficient mice develop a phenotype resembling human aging. Laboratory and clinical data suggest a favorable effect of klotho on atherosclerosis, high blood pressure, and metabolic syndrome. Therefore, we aimed to study the effect of klotho treatment on atherogenesis, blood pressure, and metabolic parameters in experimental rodent models. Fructose-fed Sprague-Dawley rats (metabolic syndrome model) and apolipoprotein E (apoE -/-) knock-out mice (atherosclerosis model) were treated with either klotho or its active domain KL1. In apoE -/- mice, klotho unexpectedly elevated plasma cholesterol and triglyceride levels compared to the control group. Yet, it did not increase the aortic sinus atherosclerotic lesion area. In fructose-fed Sprague-Dawley rats, klotho treatment did not lower blood pressure or plasma triglyceride levels. Although KL1 treatment did not lower blood pressure or plasma insulin levels, it significantly reduced the elevation of total plasma triglyceride levels (from 2.3-fold to 1.6-fold, p<0.05) due to lower triglyceride-rich VLDL levels. Klotho did not show any beneficial effects on atherosclerosis and components of the metabolic syndrome and was associated with increased plasma cholesterol levels. On the other hand, treatment with KL1 may lower plasma triglyceride levels independent of insulin. Additional studies are required in order to decipher the complex role of klotho and its active domains in the regulation of plasma lipid levels.

Functional variant of KLOTHO: a breast cancer risk modifier among BRCA1 mutation carriers of Ashkenazi origin

Klotho is a transmembrane protein that can be shed and act as a circulating hormone and is a putative tumor suppressor in breast cancer. A functional variant of KLOTHO (KL-VS) contains two amino acid substitutions F352V and C370S and shows reduced activity. Germ-line mutations in BRCA1 and BRCA2 substantially increase lifetime risk of breast and ovarian cancers. Yet, penetrance of deleterious BRCA1 and BRCA2 mutations is incomplete even among carriers of identical mutations. We examined the association between KL-VS and cancer risk among 1115 Ashkenazi Jewish women: 236 non-carriers, 631 BRCA1 (185delAG, 5382insC) carriers and 248 BRCA2 (6174delT) carriers. Among BRCA1 carriers, heterozygosity for the KL-VS allele was associated with increased breast and ovarian cancer risk (hazard ratio 1.40, 95% confidence intervals 1.08-1.83, P=0.01) and younger age at breast cancer diagnosis (median age 48 vs 43 P=0.04). KLOTHO and BRCA2 are located on 13q12, and we identified linkage disequilibrium between KL-VS and BRCA2 6174delT mutation. Studies in breast cancer cells showed reduced growth inhibitory activity and reduced secretion of klotho F352V compared with wild-type klotho. These data suggest KL-VS as a breast and ovarian cancer risk modifier among BRCA1 mutation carriers. If validated in additional cohorts, the presence of KL-VS may serve as a predictor of cancer risk among BRCA1 mutation carriers.

Functional variant of the tumor suppressor klotho: a novel risk modifier for breast cancer among BRCA1/2 carriers

Abstract #1041

Background: The aging suppressor klotho is a transmembrane protein which is expressed in the kidneys, brain and hormone-responsive tissues and can be shed and act as a circulating hormone. The klotho gene is located on chromosome 13q12, about 700,000 base-pairs upstream to the BRCA2 gene. Klotho is a potent inhibitor of the insulin-like growth factor (IGF)-1 signaling pathway. We have recently found high klotho expression in normal breast tissue and low expression in breast cancer. Over-expression of klotho suppressed growth and inhibited the IGF-1 pathway in breast cancer cells. These data suggest klotho as a tumor suppressor gene in breast cancer. A single nucleotide polymorphism (SNP) in the klotho gene results in an amino acid substitution, F325V, which is associated with altered activity of klotho and reduced lifespan in human. As BRCA mutations may be associated with increased expression of IGF-1 and its receptor in breast cancer, we hypothesized that klotho functional variant may be associated with increased cancer risk among BRCA mutations carriers.&#x2028; Material and Methods: The presence of F325V variant was evaluated using exon-specific polymerase chain reaction followed by restriction enzyme analysis, in a cohort of 784 Israeli women consisting of 236 non-BRCA mutations carriers (healthy: 109, breast cancer: 94, ovarian cancer: 33), 340 BRCA1 185delAG and 5382insC mutation carriers (healthy: 138, breast cancer: 142, ovarian cancer: 60) and 208 BRCA2 6174delT carriers (healthy: 75, breast cancer: 106, ovarian cancer: 27).&#x2028; Results: Similar distribution of the F325V variant was noted in non-carriers and BRCA1 carriers (FF, wild-type 78%; FV, heterozygous 19%; VV, recessive 3%). However, F352V was over-represented among BRCA2 carriers: FF 25%, FV 50% and VV 25%. Analysis of additional SNPs indicated linkage disequilibrium between FV and BRCA2 6174delT mutation. Yet, among BRCA2 carriers, FF was significantly more frequent among healthy individuals compared to cancer patients (18% vs. 6% respectively, p=0.02). Surprisingly, among BRCA1 carriers FV status was associated with significantly younger age at breast cancer presentation compared to FF status (38±1.8 vs. 46±1.6 years respectively, p&lt;0.001). Association between FV status and age at ovarian cancer presentation among BRCA1 carriers could not be assessed due to small sample size. No association was noted between the klotho functional variant and age at presentation among non-carriers of BRCA mutations.&#x2028; Discussion: Taken together, these data suggest klotho F352V functional variant as a novel risk modifier among BRCA mutation carriers but not among non-carriers. As BRCA1/2 mutations can enhance and wild type klotho inhibits the activity of the IGF-1 signaling in cancer, it is possible that the presence of the less active variant of klotho attenuates this balance, thus leading to enhanced activation of the pathway. If validated by additional studies, the presence of the F352V klotho variant may serve as a predictor of cancer risk among BRCA mutation carriers and may also be a novel target for cancer therapy.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1041.

Klotho: a tumor suppressor and a modulator of the IGF-1 and FGF pathways in human breast cancer

Klotho is an anti-aging gene, which has been shown to inhibit the insulin and insulin-like growth factor 1 (IGF-1) pathways in mice hepatocytes and myocytes. As IGF-1 and insulin regulate proliferation, survival and metastasis of breast cancer, we studied klotho expression and activities in human breast cancer. Immunohistochemistry analysis of klotho expression in breast tissue arrays revealed high klotho expression in normal breast samples, but very low expression in breast cancer. In cancer samples, high klotho expression was associated with smaller tumor size and reduced KI67 staining. Forced expression of klotho reduced proliferation of MCF-7 and MDA-MB-231 breast cancer cells, whereas klotho silencing in MCF-7 cells, which normally express klotho, enhanced proliferation. Moreover, forced expression of klotho in these cells, or treatment with soluble klotho, inhibited the activation of IGF-1 and insulin pathways, and induced upregulation of the transcription factor CCAAT/enhancer-binding protein beta, a breast cancer growth inhibitor that is negatively regulated by the IGF-1-AKT axis. Co-immunoprecipitation revealed an interaction between klotho and the IGF-1 receptor. Klotho is also a known modulator of the fibroblast growth factor (FGF) pathway, a pathway that inhibits proliferation of breast cancer cells. Studies in breast cancer cells revealed increased activation of the FGF pathway by basic FGF following klotho overexpression. Klotho did not affect activation of the epidermal growth factor pathway in breast cancer cells. These data suggest klotho as a potential tumor suppressor and identify it as an inhibitor of the IGF-1 pathway and activator of the FGF pathway in human breast cancer.

Mechanisms for Growth Factor-Induced Pituitary Tumor Transforming Gene-1 Expression in Pituitary Folliculostellate TtT/GF Cells

PTTG1, a securin protein, also behaves as a transforming gene and is overexpressed in pituitary tumors. Because pituitary folliculostellate (FS) cells regulate pituitary tumor growth factors by paracrine mechanisms, epidermal growth factor (EGF) receptor (EGFR)-mediated PTTG1 expression and cell proliferation was tested in pituitary FS TtT/GF cells. EGFR ligands caused up to 3-fold induction of Pttg1 mRNA expression, enhanced proliferating cell nuclear antigen, and increased entry of G0/1-arrested cells into S-phase. PTTG binding factor mRNA expression was not altered. EGF-induced Pttg1 expression and cell proliferation was abolished by preincubation of TtT/GF cells with EGFR inhibitors AG1478 and gefitinib. Phosphatidylinositol 3 kinase, protein kinase C, and MAPK, but not c-Jun N-terminal kinase and Janus activating kinase signaling regulated EGF-induced Pttg1, as well as proliferating cell nuclear antigen mRNA expression and entry into S-phase. EGF-induced EGFR and ERK1/2 phosphorylation was followed by rapid MAPK kinase/ERK kinase-dependent activation of Elk-1 and c-Fos. EGF-induced Pttg1 expression peaked at the S-G2 transition and declined thereafter. Pttg1 cell cycle dependency was confirmed by suppression of EGF-induced Pttg1 mRNA by blockade of cells in early S-phase. The results show that PTTG1 and its binding protein PTTG binding factor are expressed in pituitary FS TtT/GF cells. EGFR ligands induce PTTG1 and regulate S-phase, mediated by phosphatidylinositol 3 kinase, protein kinase C, and MAPK pathways. PTTG1 is therefore a target for EGFR-mediated paracrine regulation of pituitary cell growth.

15-Hydroxyprostaglandin dehydrogenase (PGDH) is an aberrant tumor suppressor in human breast cancer

10550

Background: Prostaglandin E2 plays a growth stimulatory role in breast cancer; and the rate-limiting enzyme in its synthesis, cyclooxygenase-2 (COX-2), is over-expressed in breast cancers. However, little is known about the expression pattern and activities of the key prostaglandin catabolic enzyme PGDH, in breast cancer pathogenesis. Methods: 5-aza-2’-deoxycytidine and suberoyl anilide bishydroxamide (SAHA) were used to unmask epigenetically silenced genes. DNA and RNA were extracted from tumors and cell lines using standard methods, and bisulfite sequencing was used for methylation analysis. Western blotting and real time PCR were used for expression analysis, and PGDH expression vector and PGDH-directed siRNA were used for overexpression and downregulation of PGDH, respectively. Athymic mice were utilized for xenograft models. Results: Using a pharmacologically based, genome-wide screen for epigenetically silenced genes, we found low levels of PGDH in MDA-MB-231 cells (estrogen receptor- (ER) and HER2-negative), but high levels in MCF-7 cells (ER-positive, HER2-negative), and observed upregulation of this enzyme following demethylation treatment. Methylation analysis revealed methylation of the PGDH promoter in one breast cancer cell line and in 3 of 10 primary tumors. Analysis of PGDH expression demonstrated low levels in 40% of primary breast tumors and identified a correlation between PGDH and ER expression. Upregulation of PGDH levels in MDA-MB-231 cells decreased their clonal growth and reduced their ability to form tumors in athymic mice. In contrast, silencing of PGDH in MCF-7 cells increased proliferation and enhanced in-vivo tumorigenicity. Further analysis revealed upregulation of aromatase following silencing of PGDH and inhibition of the ER pathway by forced expression of the enzyme. PGDH levels were downregulated by estrogen but upregulated by the tumor suppressor gene C/EBPα. Conclusions: Our results identify for the first time, that PGDH, the COX-2 antagonist, is aberrantly silenced in breast cancer. Activation of this enzyme, particularly in ER- and HER2-negative tumors, now becomes an interesting target for clinical studies.

No significant financial relationships to disclose.

PTR-3173 (somatoprim), a novel somatostatin analog with affinity for somatostatin receptors 2, 4 and 5 is a potent inhibitor of human GH secretion

SS, a natural cyclic tetradecapeptide, is a potent suppressor of pituitary GH and TSH secretion. At least five distinct SS receptor (SSTR) subtypes have been cloned and termed SSTRs 1-5. Both SSTR2 and SSTR5 regulate human GH and TSH secretion. Recently, a novel enzymatically stable SS analog, PTR-3173 (Somatoprim), with affinity for human SSTR2, SSTR4 and SSTR5, has been identified. This cyclic heptapeptide analog suppressed rat GH in vivo with no effect on insulin and minimal effect on glucagon secretion. Using primary cultures of human fetal pituitaries (20-24-week gestation) and GH-secreting adenomas, we studied the in vitro inhibitory effects of PTR-3173 on human pituitary secretion. PTR-3173 suppressed GH release from both fetal pituitaries (maximal suppression of 54% with 10 nM) and cultures of GH-cell adenomas (35% suppression with 100 nM). Octreotide and PTR-3173 had comparable inhibitory effects on GH secretion from fetal human pituitaries. TSH was mildly suppressed by PTR-3173, whereas ACTH secretion was not affected in fetal pituitary cultures. In cultures of eight GH-secreting adenomas, octreotide was superior to PTR-3173 in suppressing GH from two adenomas, PTR-3173 was more potent in three other tumors, and three adenomas did not respond significantly to either analog. PTR-3173 suppressed PRL in several mixed GH-PRL adenomas. In conclusion, PTR-3173, a novel SS analog with a unique SSTRs binding combination, is a potent in vitro suppressor of human GH. Combining this inhibitory effect with the lack of effect on insulin secretion, it is suggested that PTR-3173 may be clinically useful for the treatment of acromegaly.

Ovarian hyperstimulation without elevated serum estradiol associated with pure follicle-stimulating hormone-secreting pituitary adenoma

We report a unique case of a 28-yr-old woman with a gonadotroph adenoma secreting FSH, presented with ovarian hyperstimulation, without elevation of serum estradiol. She presented with abdominal pain and large ovaries (both 10 cm in diameter) with multiple follicular cysts shortly after discontinuing oral contraceptive pills. She had a supranormal PRL level of 71 microg/liter (normal, <20), FSH of 8.4-9.2 IU/liter (normal for follicular phase, 2.4-10), LH of 0.01 IU/liter (normal, 1.6-9.3), estradiol of 108 pmol/liter (normal for follicular phase, 80-790), and free alpha-subunit level of 0.11 microg/liter (normal, <1.8). A nuclear magnetic resonance study revealed invasive pituitary macroadenoma, 30 mm in diameter. Dopamine agonist (cabergoline) treatment normalized serum PRL but had no affect on FSH levels. A transsphenoidal surgery was performed, and most of the adenoma was resected. One month after surgery the patient resumed menstruation, and the hormonal profile included serum FSH of 6.3 IU/liter, LH of 2.1 IU/liter, estradiol of 156 pmol/liter, and PRL of 10 microg/liter. The excised adenoma tissue exhibited intense immunostaining for FSH and secreted this hormone to culture medium. Stimulation with TRH (both in vivo preoperatively and in vitro study of the excised tumor) had no effect on FSH secretion from the adenoma. Estradiol did not suppress FSH release from cultured adenoma cells. Patient serum samples showed significant FSH bioactivity when tested in a human granulosa cell line. This case is remarkable because the ovarian hyperstimulation related to the FSH-secreting adenoma was not associated with high levels of serum estradiol, probably due to insufficient LH production by the normal pituitary. Thus, it supports the two-cell, two-gonadotropin theory, that both FSH and LH are necessary for normal ovarian estrogen production.

Prolactin (PRL)-releasing peptide stimulates PRL secretion from human fetal pituitary cultures and growth hormone release from cultured pituitary adenomas

The hypothalamic peptide PRL-releasing peptide (PrRP) has recently been cloned and identified as a ligand of an orphan pituitary receptor that stimulates in vitro PRL secretion. PrRP also induces PRL release in rats in vivo, especially in normal cycling females. However, no information on the effects of PrRP in the human is available. To elucidate the role of PrRP in regulating human anterior pituitary hormones, we used human PrRP-31 in primary cultures of human pituitary tissues, including fetal (20--27 weeks gestation) and normal adult pituitaries, as well as PRL- and GH-secreting adenomas. PrRP increased PRL secretion from human fetal pituitary cultures in a dose-dependent manner by up to 35% (maximal effect achieved with 10 nM), whereas TRH was slightly more potent for PRL release. Coincubation with estradiol resulted in enhanced fetal PRL response to PrRP, and GH release was only increased in the presence of estradiol. Although PRL secretion from PRL-cell adenomas was not affected by PrRP, PrRP induced PRL release from cultures of a GH-cell adenoma that cosecreted PRL. PrRP enhanced GH release in several GH-secreting adenomas studied by 25--27%, including GH stimulation in a mixed PRL-GH-cell tumor. These results show for the first time direct in vitro effects of PrRP-31 on human pituitary cells. PrRP is less potent than TRH in releasing PRL from human fetal lactotrophs and is unable to release PRL from PRL-cell adenomas in culture, but stimulated GH from several somatotroph adenomas. Thus, PrRP may participate in regulating GH, in addition to PRL, in the human pituitary.

The fidelity of 3' misinsertion and mispair extension during DNA synthesis exhibited by two drug-resistant mutants of the reverse transcriptase of human immunodeficiency virus type 1 with Leu74-->Val and Glu89-->Gly

The relatively low fidelity of DNA synthesis characteristic to the reverse transcriptases (RTs) of the AIDS-causing viruses, human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2, respectively) was implicated as a dominant factor that contributes to the genetic hypervariability of these viruses. The formation of 3'-mispaired DNA and the subsequent extension of this DNA were shown to be key determinants that lead to the error proneness of these RTs. As part of our goal to study the structure/function relationship in HIV-1 RT, we have conducted mutational studies aimed at identifying amino-acid residues involved in affecting the fidelity of DNA synthesis by the enzyme. We have recently found that two mutants of HIV-1 RT, which show resistance to nucleoside analog inhibitors ([Leu184]RT and [Phe183]RT), exhibit in vitro error proneness of DNA synthesis lower than that of wild-type enzyme [Bakhanshvili, M., Avidan, O. & Hizi, A. (1996) Mutational studies of human immunodeficiency virus type 1 reverse transcriptase: the involvement of residues 183 and 184 in the fidelity of DNA synthesis, FEBS Lett. 391, 257-262]. Using both criteria, the current comparative study suggests that these two mutant RTs display a substantially enhanced fidelity of DNA synthesis relative to the wild-type RT counterpart. In the current study we have analyzed two additional drug-resistant mutants of HIV-1 RT, [Val74]RT and [Gly89]RT, for their in vitro fidelity of DNA synthesis using two parameters of DNA synthesis: 3' mispair formation and elongation of 3'-mismatched DNA. The current comparative study suggests that these two mutant RTs display a substantially enhanced fidelity of DNA synthesis relative to the wild-type RT counterpart, using both criteria. Analysis of the relative frequencies of misinsertion and mispair extension indicates that the overall error proneness of DNA synthesis in HIV-1 RT is wild-type > [Val74]RT > [Gly89]RT mutant. The results further support the possible linkage between the capacity of an enzyme to incorporate a nucleoside analog instead of the correct dNTP (leading to drug sensitivity) and the ability to incorporate and extend a wrong nucleotide (resulting in mutagenesis). Our results may bear on the potential use of selecting and maintaining HIV virions with high fidelity and drug-resistant RTs to suppress the subsequent appearance of virions resistant to other drugs.

Analysis of HIV-2 RT mutants provides evidence that resistance of HIV-1 RT and HIV-2 RT to nucleoside analogs involves a repositioning of the template-primer

Mutations that confer resistance to nucleoside analogs do not cluster around the deoxynucleotide triphosphate (dNTP) binding site. Instead, these mutations appear to lie along the groove in the enzyme where the template-primer binds. Based on such structural data and on complementary biochemical analyses, it has been suggested that resistance to nucleoside analogs involves repositioning of the template-primer. We have prepared mutations in HIV-2 RT that are the homologs of mutations that confer resistance to nucleoside analogs in HIV-1 RT. Analysis of the behavior of HIV-2 RT mutants (Leu74Val, Glu89Gly, Ser215Tyr, Leu74Val/Ser215Tyr and Glu89Gly/Ser215Tyr) in vitro confirms the results obtained with HIV-1 RT: resistance is a function of the length of the template overhang. These analyses also suggest that the homolog in HIV-2 RT of one of the mutations that confers resistance to AZT in HIV-1 RT (Thr215Tyr) confers resistance by repositioning of the template-primer.

Resistance to nucleoside analogs of selective mutants of human immunodeficiency virus type 2 reverse transcriptase

We have studied selected mutants of human immunodeficiency virus type 2 (HIV-2) reverse transcriptase (RT) in a cell-free system in order to assess whether the mutant proteins exhibit a reduction in the sensitivity to nucleoside analog inhibitors similar to that of HIV-1 RT. We have modified, by site-directed mutagenesis, several of those amino acid residues so that their equivalent substitutions in HIV-1 RT have led to the formation of HIV-1 RT variants with the highest degree of resistance to dideoxynucleoside triphosphates (i.e., Glu-89-->Gly, Leu-74-->Val, and Ser-215-->Tyr [which is comparable to the Thr-215-->Tyr mutation of HIV-1 RT] and the double mutations Glu-89-->Gly/Ser-215-->Tyr and and Leu-74-->Val/Ser-215-->Tyr). The similarity found between resistance of the newly generated HIV-2 RT mutants to nucleoside analogs and that of the comparable mutants of HIV-1 RT can support the notion that the overall protein folding around the DNA polymerase active site in HIV-2 RT is quite similar to that of HIV-1 RT.

Inhibition of reverse transcriptase of human immunodeficiency virus type 1 and chimeric enzymes of human immunodeficiency viruses types 1 and 2 by two novel non-nucleoside inhibitors

We have studied the effects of two non-nucleoside reverse transcriptase inhibitors (NNRTI), nitrophenyl phenyl sulfone (NPPS) and a potent derivative of oxathiin carboxanilide (UC-38), on enzymatically active molecular chimeras composed of complementary segments of the reverse transcriptases (RTs) of human immunodeficiency virus type 1 (HIV-1) and -2 (HIV-2). The substances inhibit only the DNA polymerase activity of HIV-1 RT with no effect on HIV-2 RT. The results suggest that there is a protein segment located between residues 158 and 190 that is critical for the inhibition by both compounds. However, there is probably a second segment that resides between residues 192 and 202, as in the case of NPPS, or residues 203 and 224, as in the case of UC-38, that is also crucial for the sensitivity of HIV-1 RT to both inhibitors.

The catalytic properties of the reverse transcriptase of the lentivirus equine infectious anemia virus

The reverse transcriptase (RT) of equine infectious anemia virus (EIAV) shares sequence similarity with the RTs of other lentiviruses, particularly with the RTs of human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2, respectively), the causative agents of acquired immunodeficiency syndrome (AIDS). There is a 41-42% sequence identity between EIAV RT and both HIV RTs (which have 61% sequence identity to each other). We have compared the enzymic properties of EIAV RT with those of HIV-1 RT. Several aspects of the activities of EIAV RT differ from the corresponding activities of HIV-1 RT. There are significant differences in the inhibition of the DNA polymerase activities by the deoxynucleoside triphosphate analogs, 3'-azido-2,3'-dideoxythymidine triphosphate, dideoxyTTP and dideoxyGTP and by the nonnucleoside inhibitor, tetrahydroimidazo[4,5,1-jk-1,4]benzodiazepin-2-(1H)-one and thione; in the dependence of DNA polymerase and RNase H activities on pH; in the inhibition of the DNA polymerase activities by the thiol-specific reagent N-ethylmaleimide; in the specific DNA polymerase activity; in the inhibition of the ribonuclease H activity by the zinc chelator orthophenanthroline. However, there are several cases in which EIAV RT and HIV-1 RT are more similar than was previously found for HIV-1 RT and HIV-2 RT. These include the Km values for the DNA polymerase activities, the heat stability of the DNA polymerase functions and the specific activity of the RNase H function.

Arachidonic acid increases the activity of the assembled NADPH oxidase in cytoplasmic membranes and endosomes

The effect of arachidonic acid (AA) on the assembled NADPH oxidase activity in cytoplasmic membranes and in endosomes separated from human neutrophils was studied. These two fractions were separated on a Percoll-sucrose density gradient from PMA-stimulated neutrophils preincubated with fluorescein isothiocyanate-conjugated dextran (FITC-dextran). In both fractions, NADPH oxidase activity could be detected with the addition of NADPH and cytochrome c, indicating the presence of an assembled activated form of the enzyme. Addition of AA at low concentrations (ED50 = 1 microM and 0.1 microM for cytoplasmic membranes and FITC-dextran endosomes, respectively) caused an increase in the activity of the assembled NADPH oxidase found in these fractions. Addition of 10 microM AA to the assembled oxidase in cytoplasmic membranes or endosomes significantly increased the Vmax (1.37 and 1.45 nmol O2/min compared with 2.05 and 2.20 nmol O2/min in the absence of presence of AA, respectively) and lowered the Km for NADPH (35 microM and 40 microM compared with 7.5 microM and 7.2 microM in the absence or presence of AA, respectively). These results suggest that AA increases the activity of the assembled NADPH oxidase by elevating the number of its active forms and increasing its affinity to the substrate.

Diversity in peritoneal macrophage response of CAPD patients to 1,25-dihydroxyvitamin D3

A major complication of continuous ambulatory peritoneal dialysis (CAPD) is peritonitis. Increasing the activity of the peritoneal macrophages, the predominant cell type found in the peritoneal cavity, may be a promising treatment for this infection. The effect of 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] on the activity of peritoneal macrophages from CAPD patients and nonuremic controls was studied. 1,25(OH)2D3 had a biphasic effect on superoxide generation in the concentration range of 2.5 10(-9) M to 5 x 10(-6) M with a peak at 2 x 10(-8) M. The addition of 2 x 10(-8) M 1,25(OH)2D3 to nonuremic control macrophages for 24 hours caused a significant twofold increase in superoxide generation in response to phorbol myristate acetate (PMA), from 2.21 + 0.2 to 4.1 + 0.2 nmol/10(6) mac (P less than 0.001), and enhanced the bactericidal activity from 60 + 7% to 85 + 9% (P less than 0.005). CAPD patients were divided into two groups: Group A, patients with high peritonitis incidence (HPI); group B, patients with low peritonitis incidence (LPI). Macrophages from HPI patients show a lower bactericidal activity (37 +/- 5%) and were not affected by 1,25(OH)2D3 after 24 hours of treatment. The increase in macrophage activity was seen only after three days of incubation with the hormone. Macrophages from this group generated a high amount of prostaglandin E2 (PGE2) during the first 24 hours in culture (7.8 +/- 0.52 ng/ml as compared with 0.35 +/- 0.03 ng/ml in the controls).(ABSTRACT TRUNCATED AT 250 WORDS)