Survival of Patients with Metastatic Prostate Cancer After Disease Progression on an Androgen Receptor Axis-Targeted Therapy Given in the Metastatic Castration-Sensitive Versus Metastatic Castration-Resistant Prostate Cancer Setting

Androgen receptor axis-targeted therapies (ARATs; androgen receptor or androgen synthesis inhibitors) have been approved for the treatment of patients with metastatic castration-sensitive and castration-resistant prostate cancer (mCSPC and mCRPC) on the basis of improved overall survival (OS) in randomized clinical trials. However, it is not clear whether the OS for patients after progression on first-line ARAT differs if the first ARAT was administered in the mCSPC versus mCRPC setting and what its estimates are. We assessed the OS after disease progression on ARAT given as first-line therapy in mCSPC versus mCRPC. Patient-level data were collected retrospectively, and only those treated with first-line ARAT for mCSPC or mCRPC were included. For patients receiving ARAT in the mCRPC setting, no prior ARAT was allowed in the mCSPC setting. The median OS and hazard ratio (HR) were determined via Kaplan-Meier analysis from the time of progression on ARAT. Of 382 patients treated with first-line ARAT, 172 (44 mCSPC and 128 mCRPC) had experienced disease progression and were included in the analysis. Median OS was similar in the mCSPC (23 mo) and mCRPC (17 mo) settings (HR 0.99, 95% confidence interval 0.62-1.56; p = 0.95). A total of 138 patients received subsequent systemic therapy after progression. Our results suggest that median OS is similar after progression on one ARAT, whether given in the first-line mCSPC or first-line mCRPC setting, and is estimated to be <2 yr. These data have implications for patient prognostication and the design of clinical trials in the post-ARAT setting for further drug development. PATIENT SUMMARY: We investigated whether the survival benefit differs between metastatic castration-sensitive and castration-resistant prostate cancer for patients who have already experienced cancer progression after first-line treatment with one drug targeting the androgen receptor pathway  (called ARAT). We found that the median survival benefit was less than 2 years and was similar for the two groups.

External Validation of Association of Baseline Circulating Tumor Cell Counts with Survival Outcomes in Men with Metastatic Castration-Sensitive Prostate Cancer

Approximately 20% of men with metastatic castration-sensitive prostate cancer (mCSPC) progress within 1 year of treatment, and biomarkers to identify them up front are lacking. In a randomized phase III trial in men with mCSPC (SWOG S1216), higher baseline circulating tumor cells (CTCs) were prognostic of inferior outcomes. We aimed to validate these findings and interrogate corresponding tumor genomic profiles. Consecutively seen men with newly diagnosed mCSPC undergoing systemic therapy and baseline CTC enumeration by CellSearch assay were included. Gene alterations were determined by comprehensive genomic profiling of tumor tissue by Clinical Laboratory Improvement Amendments-certified lab. The relationship between categorized CTC counts and both progression-free survival (PFS) and overall survival (OS) was assessed in the context of Cox proportional hazards models, both unadjusted and adjusted for age, Gleason score, PSA at androgen-deprivation therapy initiation, disease volume, de novo status, treatment intensification, and number of altered genes. Overall, 103 patients were included in the analysis. On multivariate analysis high CTCs (≥ 5 vs. 0) were associated with poorer PFS [HR, 4.52; 95% confidence interval (CI), 1.84-11.11; P = 0.001) and OS (HR, 3.59; 95% CI, 0.95-13.57; P = 0.060). Patients with higher CTC counts had a greater number of altered genes and total number of alterations (all P < 0.02). In this article, for the first time, we externally validate the association of higher CTC counts with inferior survival outcomes in men with mCSPC and show a distinct associated tumor genomic landscape. These findings may improve prognostication, patient counseling, and treatment selection in men with mCSPC.

SPOP Mutations as a Predictive Biomarker for Androgen Receptor Axis-Targeted Therapy in De Novo Metastatic Castration-Sensitive Prostate Cancer

PURPOSE

Intensification of androgen deprivation therapy (ADT) with either docetaxel or androgen receptor axis-targeted therapies (ARAT) are the current standard of care for patients with metastatic castration-sensitive prostate cancer (mCSPC). However, biomarkers guiding treatment selection are lacking. We hypothesized that ADT intensification with ARAT, but not with docetaxel, would be associated with improved outcomes in patients with de novo (dn)-mCSPC harboring SPOP mutations.

EXPERIMENTAL DESIGN

Patient-level data from a deidentified nationwide (U.S.-based) prostate cancer clinico-genomic database between January 2011 and December 2021 were extracted. Eligibility criteria: diagnosis of metastatic disease within 30 days of original prostate cancer diagnosis, genomic profiling of a tissue biopsy collected within 90 days of original diagnosis, and initiation of ARAT or docetaxel within 120 days of initial diagnosis. The log-rank test and Cox proportional hazards models were used to compare time to castration-resistant prostate cancer (TTCRPC) and overall survival (OS) for patients with and without SPOP mutations undergoing ADT intensification with ARAT or docetaxel.

RESULTS

In the ARAT cohort, presence of SPOP mutation compared with wild-type was associated with more favorable TTCRPC [not reached (NR) vs. 16.7 months; adjusted HR (aHR), 0.20; 95% confidence interval (CI), 0.06-0.63; P = 0.006] and OS (NR vs. 27.2 months; aHR, 0.19; 95% CI, 0.05-0.79; P = 0.022). In contrast, SPOP mutation status was not associated with TTCRPC or OS in docetaxel-treated cohort.

CONCLUSIONS

In real-world settings, SPOP mutations were associated with improved outcomes to ADT plus ARAT (but not ADT plus docetaxel) in patients with dn-mCSPC. This may serve as a predictive biomarker to guide treatment selection for patients with mCSPC.

Genomic landscape of advanced prostate cancer patients with BRCA1 versus BRCA2 mutations as detected by comprehensive genomic profiling of cell-free DNA

BRCA1-mutated prostate cancer has been shown to be less responsive to poly (ADP-ribose) polymerase (PARP) inhibitors as compared to BRCA2-mutated prostate cancer. The reason for this differential response is not clear. We hypothesized this differential sensitivity to PARP inhibitors may be explained by distinct genomic landscapes of BRCA1 versus BRCA2 co-segregating genes. In a large dataset of 7,707 men with advanced prostate cancer undergoing comprehensive genomic profiling (CGP) of cell-free DNA (cfDNA), 614 men harbored BRCA1 and/or BRCA2 alterations. Differences in the genomic landscape of co-segregating genes was investigated by Fisher's exact test and probabilistic graphical models (PGMs). Results demonstrated that BRCA1 was significantly associated with six other genes, while BRCA2 was not significantly associated with any gene. These findings suggest BRCA2 may be the main driver mutation, while BRCA1 mutations tend to co-segregate with mutations in other molecular pathways contributing to prostate cancer progression. These hypothesis-generating data may explain the differential response to PARP inhibition and guide towards the development of combinatorial drug regimens in those with BRCA1 mutation.

Identification of Somatic Gene Signatures in Circulating Cell-Free DNA Associated with Disease Progression in Metastatic Prostate Cancer by a Novel Machine Learning Platform

PURPOSE

Progression from metastatic castration-sensitive prostate cancer (mCSPC) to a castration-resistant (mCRPC) state heralds the lethal phenotype of prostate cancer. Identifying genomic alterations associated with mCRPC may help find new targets for drug development. In the majority of patients, obtaining a tumor biopsy is challenging because of the predominance of bone-only metastasis. In this study, we hypothesize that machine learning (ML) algorithms can identify clinically relevant patterns of genomic alterations (GAs) that distinguish mCRPC from mCSPC, as assessed by next-generation sequencing (NGS) of circulating cell-free DNA (cfDNA).

EXPERIMENTAL DESIGN

Retrospective clinical data from men with metastatic prostate cancer were collected. Men with NGS of cfDNA performed at a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory at time of diagnosis of mCSPC or mCRPC were included. A combination of supervised and unsupervised ML algorithms was used to obtain biologically interpretable, potentially actionable insights into genomic signatures that distinguish mCRPC from mCSPC.

RESULTS

GAs that distinguish patients with mCRPC (n = 187) from patients with mCSPC (n = 154) (positive predictive value = 94%, specificity = 91%) were identified using supervised ML algorithms. These GAs, primarily amplifications, corresponded to androgen receptor, Mitogen-activated protein kinase (MAPK) signaling, Phosphoinositide 3-kinase (PI3K) signaling, G1/S cell cycle, and receptor tyrosine kinases. We also identified recurrent patterns of gene- and pathway-level alterations associated with mCRPC by using Bayesian networks, an unsupervised machine learning algorithm.

CONCLUSION

These results provide clinical evidence that progression from mCSPC to mCRPC is associated with stereotyped concomitant gain-of-function aberrations in these pathways. Furthermore, detection of these aberrations in cfDNA may overcome the challenges associated with obtaining tumor bone biopsies and allow contemporary investigation of combinatorial therapies that target these aberrations.

IMPLICATIONS FOR PRACTICE

The progression from castration-sensitive to castration-resistant prostate cancer is characterized by worse prognosis and there is a pressing need for targeted drugs to prevent or delay this transition. This study used machine learning algorithms to examine the cell-free DNA of patients to identify alterations to specific pathways and genes associated with progression. Detection of these alterations in cell-free DNA may overcome the challenges associated with obtaining tumor bone biopsies and allow contemporary investigation of combinatorial therapies that target these aberrations.

Quest for Ideal Composite Biomarkers for Response to Immunotherapies

In the CheckMate 275 study, composite biomarkers appear to better predict response to immunotherapy over individual ones. Nevertheless, the path forward needs consensus guidelines for biomarker interpretation. Thereafter, prospective validation with real-time, serial biospecimen collection along with the development of composite biomarker models leads to the goal of personalized therapy.

See related article by Galsky et al., p. 5120

Comprehensive Analysis of AR Alterations in Circulating Tumor DNA from Patients with Advanced Prostate Cancer

BACKGROUND

Somatic alterations in circulating tumor DNA (ctDNA) may be associated with treatment response or prognosis in prostate cancer (PCa). The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in ctDNA from patients with PCa and to further understand the somatic genetic heterogeneity of advanced prostate cancer.

PATIENTS AND METHODS

This study included a heterogeneous group of 892 patients with advanced PCa (predominantly castrate-resistant prostate cancer) with AR alterations detected in ctDNA that underwent next-generation sequencing of 54 to 73 genes via Guardant360 testing (Guardant Health, Inc., Redwood City, CA). Distribution and summary of AR alterations detected, the association of AR alterations with other genes, and a pathway analysis are reported.

RESULTS

The median absolute plasma copy number of AR amplifications was 3.3 (range, 1.2-165.2). Many patients had multiple AR mutations; a total of 112 unique mutations were identified in AR, including L702H (25%), T878A (14%), H875Y (11%), W742C (8%), W742L (4%), F877L (2%), and T878S (2%). Other ctDNA gene alterations in the Guardant assays included TP53 (50%), MYC (34%), BRAF (32%), PIK3CA (29%), MET (25%), CDK6 (26%), EGFR (24%), FGFR1 (21%), and APC (12%). Many of these non-AR alterations are not tissue verified in other studies. AR amplification cosegregated with alterations in MYC (p < .001), BRAF (p < .001), PIK3CA (p < .001), MET (p < .001), CDK6 (p < .001), EGFR (p < .001), FGFR1 (p = .391), and more. Alterations in APC were significantly associated with mutations in AR (p < .001).

CONCLUSION

Several AR alterations and concomitant non-AR alterations that associate with drug resistance were detected. These findings provide additional insights into the heterogeneity of advanced prostate cancer.

IMPLICATIONS FOR PRACTICE

The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in circulating tumor DNA (ctDNA) from patients with prostate cancer in relation to non-AR gene alterations detected in the ctDNA landscape. The study included 892 patients with prostate cancer with AR alterations in ctDNA. AR alterations were significantly associated with other gene alterations detected in ctDNA. The common AR mutations found are linked to resistance to abiraterone, enzalutamide, or bicalutamide. Characterization of the circulating AR landscape and gene alterations provides potential additional insight into the somatic genetic heterogeneity of advanced prostate cancer.

Circulating tumor DNA alterations in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Because cell-free DNA (cfDNA) analysis facilitates the noninvasive genomic profiling of metastatic castration-resistant prostate cancer (mCRPC), the authors evaluated the association between cfDNA alterations and outcomes and evolution with therapy.

METHODS

Patients with mCRPC underwent cfDNA genomic profiling using Guardant360, which examines major cancer-associated genes. Clinical factors, therapy information, failure-free survival, and overall survival (OS) were obtained for select patients. The association between genomic alterations and outcomes was investigated.

RESULTS

Of 514 men with mCRPC, 482 (94%) had ≥1 circulating tumor DNA (ctDNA) alteration. The most common recurrent somatic mutations were in TP53 (36%), androgen receptor (AR) (22%), adenomatous polyposis coli (APC) (10%), neurofibromin 1 (NF1) (9%), epidermal growth factor receptor (EGFR), catenin beta-1 (CTNNB1), and AT-rich interactive domain-containing protein 1A (ARID1A) (6% each); and BRCA1, BRCA2, and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (5% each) The most common genes with increased copy numbers were AR (30%), MYC (20%), and BRAF (18%). Clinical outcomes were available for 163 patients, 46 of whom (28.8%) were untreated for mCRPC. A higher number of ctDNA alterations, AR alterations, and amplifications of MYC and BRAF were associated with worse failure-free survival and/or OS. On multivariable analysis, MYC amplification remained significantly associated with OS. Prior therapy and serial profiling demonstrated the evolution of alterations in AR and other genes.

CONCLUSIONS

ctDNA frequently was detected in this large cohort of "real-world" patients with mCRPC, and the alterations appeared to be similar to previously reported tumor tissue alterations. A higher number of alterations, and AR and MYC alterations, appear to compromise clinical outcomes, suggesting a role for immune checkpoint inhibitors and novel AR and BET inhibitors in selected patients.

Characterization of metastatic urothelial carcinoma via comprehensive genomic profiling of circulating tumor DNA

BACKGROUND

Biomarker-guided clinical trials are increasingly common in metastatic urothelial carcinoma (mUC), yet patients for whom contemporary tumor tissue is not available are not eligible. Technological advancements in sequencing have made cell-free circulating DNA (cfDNA) next-generation sequencing (NGS) readily available in the clinic. The objective of the current study was to determine whether the genomic profile of mUC detected by NGS of cfDNA is similar to historical tumor tissue NGS studies. A secondary objective was to determine whether the frequency of genomic alterations (GAs) differed between lower tract mUC (mLTUC) and upper tract mUC (mUTUC).

METHODS

Patients from 13 academic medical centers in the United States who had a diagnosis of mUC between 2014 and 2017 and for whom cfDNA NGS results were available were included. cfDNA profiling was performed using a commercially available platform (Guardant360) targeting 73 genes.

RESULTS

Of 369 patients with mUC, 294 were diagnosed with mLTUC and 75 with mUTUC. A total of 2130 GAs were identified in the overall mUC cohort: 1610 and 520, respectively, in the mLTUC and mUTUC cohorts. In the mLTUC cohort, frequently observed GAs were similar between cfDNA NGS and historical tumor tissue studies, including tumor protein p53 (TP53) (P = 1.000 and .115, respectively), AT-rich interaction domain 1A (ARID1A) (P = .058 and .058, respectively), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (P = .058 and .067, respectively), erb-b2 receptor tyrosine kinase 2 (ERBB2) (P = .565 and .074, respectively), and fibroblast growth factor receptor 3 (FGFR3) (P = .164 and .014, respectively). No significant difference was observed with regard to the frequency of GAs between patients with mLTUC and mUTUC.

CONCLUSIONS

Among patients with mUC for whom no tumor tissue was available, cfDNA NGS was able to identify a similar profile of GAs for biomarker-driven clinical trials compared with tumor tissue. Despite the more aggressive clinical course, cases of mUTUC demonstrated a circulating tumor DNA genomic landscape that was similar to that of mLTUC. Cancer 2018;124:2115-24. © 2018 American Cancer Society.

Siblings with severe pyruvate kinase deficiency and a complex genotype

Siblings presented as neonates with severe jaundice and transfusion-dependent hemolytic anemia. Next-generation sequencing revealed both to have three heterozygous mutations in the gene encoding erythrocyte pyruvate kinase (PKLR), plus a heterozygous splice mutation in the beta-spectrin gene (SPTB). In addition, both have a different 5th mutation in a gene encoding other erythrocyte membrane proteins. The asymptomatic parents and all three asymptomatic siblings have different sets of these mutations. © 2016 Wiley Periodicals, Inc.

Improved harmonization of eosin-5-maleimide binding test across different instruments and age groups

BACKGROUND

The eosin-5'maleimide (EMA) binding test has been studied extensively for the detection of hereditary spherocytosis (HS). Its performance characteristics have been compared to NaCl-based or glycerol lysis-based red cell osmotic fragility tests and cryohemolysis. HS samples are also better identified when both mean channel fluorescence (MCF) of EMA relative to controls and the coefficient of variation (CV) are analyzed.

METHODS

We looked at 65 normal controls including 30 adults 25-65 years old and 35 newborns and 12 HS cases. In addition to the MCF and the CV, we used a side scatter (SSC) vs. EMA fluorescence gate or "footprint" to depict where normal erythrocytes should appear. Erythrocytes that have reduced band 3 protein appear outside of the footprint.

RESULTS

In our study, newborn data did not cluster with the samples from working age individuals. The MCF and the CVs of normal newborns were higher than normal adult group. However, the footprint data of normal samples relative to their controls was around 99.5% for each group, because the footprint was moved to fit the pattern of the normal.

CONCLUSIONS

The inclusion of footprint parameter will help in better standardization as well as implementation of this test across different age groups as well as different instruments. © 2015 International Clinical Cytometry Society.

Novel α-spectrin mutation in trans with α-spectrin causing severe neonatal jaundice from hereditary spherocytosis

We evaluated a neonate with severe jaundice but a negative family history. Spherocytes were present and suspected hereditary spherocytosis was confirmed by osmotic fragility and eosin-5-maleimide erythrocyte staining. We found he was a compound heterozygote for two pathogenic mutations in the gene encoding α-spectrin: a previously reported α(LEPRA) inherited from his asymptomatic mother, and a novel α-spectrin mutation in intron 45 +1 disrupting the consensus splice site, from his asymptomatic father.

A previously unknown mutation in the pyruvate kinase gene (PKLR) identified from a neonate with severe jaundice

We report a neonate with early and severe hemolytic jaundice and low erythrocyte pyruvate kinase enzymatic activity (<2 U/g hemoglobin, reference interval 9-22). We found her asymptomatic mother to be heterozygous for a novel PKLR mutation (c.1573delT) with an erythrocyte PK activity of 6.2 U/g hemoglobin. Her asymptomatic father was heterozygous for the common Northern European PKLR mutation (c.1529A) with an erythrocyte PK activity of 3.6 U/g. The neonate was a compound heterozygote with both mutations, but with no other mutations identified by sequencing a panel of 27 genes involved in severe neonatal jaundice.

Variations in both α-spectrin (SPTA1) and β-spectrin ( SPTB ) in a neonate with prolonged jaundice in a family where nine individuals had hereditary elliptocytosis

We cared for a neonate who had problematic hyperbilirubinemia born into a family where nine first-degree relatives had hereditary elliptocytosis (HE). As neonates, the nine relatives did not have any significant jaundice or anemia that was recognizable. Blood films on the proband suggested a diagnosis of pyropoikilocytosis. Analysis of the α-spectrin gene (SPTA1) in the proband revealed two previously reported low-frequency heterozygous polymorphisms of unknown clinical significance and the α(LELY) allele. In addition, a novel heterozygous mutation was identified in exon 2 of the β-spectrin gene SPTB. No mutations were identified in ANK1 (ankyrin-1), SLC4A1 (band 3), EPB41 (band 4.1), or EPB42 (band 4.2).

Novel exon 2 α spectrin mutation and intragenic crossover: three morphological phenotypes associated with four distinct α spectrin defects

Hereditary pyropoikilocytosis is a severe hemolytic anemia caused by spectrin deficiency and defective spectrin dimer self-association, typically found in African populations. We describe two Utah families of northern European ancestry including 2 propositi with atypical non-microcytic hereditary pyropoikilocytosis, 7 hereditary elliptocytosis members and one asymptomatic carrier. The underlying molecular defect is a novel mutation in the alpha(α) spectrin gene, SPTA(R34P) that impairs spectrin tetramer formation. It is inherited in trans to the hypomorphic SPTA(αLELY) in the 2 propositi and 5 of 7 hereditary elliptocytosis individuals indicating that SPTA(αLELY) is not the sole determinant of the variable clinical expression. α Spectrin mRNA was mildly decreased in all hereditary elliptocytosis subjects, whereas both hereditary pyropoikilocytosis propositi had a severe decrease to ~10% of normal. Genotyping identified a unique SPTA intragenic crossover and uniparental disomy in one hereditary elliptocytosis individual. Two additional crossover events demonstrated the susceptibility of SPTA gene to rearrangement and revealed a novel segregation of the two SPTA(αLELY) mutations. We conclude that the profound phenotypic heterogeneity in these families can be attributed to the SPTA(R34P) mutation in combination with: 1) inheritance in trans of either SPTA(αLELY); or 2) the wild-type SPTA; 3) a decrease of α spectrin mRNA; and 4) SPTA intragenic crossover.

Identification of one or two α-globin gene deletions by isoelectric focusing electrophoresis

OBJECTIVES

To investigate the utility of isoelectric focusing electrophoresis (IEF) for identifying patients with α-thalassemia, which results from the deletion of 1 or more of the α-globin genes.

METHODS

Samples were selected based on their hemoglobin H (HbH) concentration observed using IEF. The samples were analyzed for the most common α-globin gene deletions using molecular analysis.

RESULTS

α-Globin gene deletions corresponding to α-thalassemia trait or silent carrier were observed in all samples with the HbH less than 2% phenotype. The genotypes of the specimens with HbH greater than 5% were consistent with HbH disease, while the wild-type phenotype control samples showed a wild-type genotype.

CONCLUSIONS

Low concentrations of HbH can be detected in a patient with 1 or 2 α-gene deletions using IEF.

Acute kernicterus in a neonate with O/B blood group incompatibility and a mutation in SLC4A1

We cared for a term female newborn, who at 108 hours of age, with a total serum bilirubin of 15.4 mg/dL, was discharged from the hospital on home phototherapy. At a return appointment 44 hours later, her total serum bilirubin was 41.7 mg/dL and signs of acute kernicterus were present. Maternal/fetal blood group O/B incompatibility was identified, with a negative direct antiglobulin test, which was positive on retesting. She had abundant spherocytes on blood smear, and these persisted at follow-up, but neither parent had spherocytes identified. A heterozygous SLC4A1(E508K) mutation (gene encoding erythrocyte membrane protein band 3) was found, and in silico predicted to result in damaged erythrocyte cytoskeletal protein function. No mutations were identified in other red cell cytoskeleton genes (ANK1, SPTA1, SPTB, EPB41, EPB42) and the UGT1A1 promoter region was normal. Neurologic follow-up at 2 and 4 months showed developmental delays consistent with mild kernicterus.

Best practices for use of the HEMOX analyzer in the clinical laboratory: quality control determination and choice of anticoagulant

The HEMOX Analyzer (TCS Scientific) has been used to measure the full oxygen-dissociation curve (ODC) and to calculate P(50) and the Hill coefficient. The effects of different anticoagulants on sample stability and P(50) values have not been evaluated extensively for this instrument. We characterized an artificial hemoglobin (Equil QC463) for quality control (QC) and compared P(50) values for blood samples drawn into 3 different anticoagulants (acid citrate dextrose [ACD], heparin, and EDTA). P(50) values were not stable in ACD but were stable in heparin and EDTA anticoagulants for up to 4 days. Tests with Equil QC463 showed that P(50) values were quite sensitive to small variations in buffer pH. Use of the correct anticoagulant and strict control of buffer pH are 2 parameters that need to be accounted for in best-practices use of this hemoximeter and before determining P(50).

Imatinib mesylate therapy for polycythemia vera: final result of a phase II study initiated in 2001

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm (MPN) characterized by excessive production of red blood cells. Patients with PV are at a risk of thrombosis, bleeding, and transformation to myelofibrosis or acute myeloid leukemia. Therapy for PV is based on the use of phlebotomy, aspirin, and in high-risk patients, cytoreductive agents such as hydroxyurea. Anecdotal evidence suggests that imatinib mesylate, a selective tyrosine kinase inhibitor of ABL1, ARG, PDGFR, and KIT kinases has activity in PV. We conducted an open-label phase II clinical trial of imatinib at the standard dose of 400 mg daily in 24 patients with PV. The median duration of imatinib therapy was 5.1 months (range 0.2-86.4). Overall, 4 (17%) patients responded: one had a complete and three partial hematological response. The median time to response was 17.5 months (range 6-28), and the median duration of response was 17 months (range 9-68). No significant changes in JAK2(V617F) mutation burden were noted during imatinib therapy when compared with pretreatment values (P = 0.46). Therapy with imatinib was generally well tolerated. Our data indicate that imatinib has minimal clinical activity in PV.

The JAK kinase inhibitor CP-690,550 suppresses the growth of human polycythemia vera cells carrying the JAK2V617F mutation

The somatic activating janus kinase 2 mutation (JAK2)(V617F) is detectable in most patients with polycythemia vera (PV). Here we report that CP-690,550 exerts greater antiproliferative and pro-apoptotic activity against cells harboring JAK2(V617F) compared with JAK2(WT). CP-690,550 treatment of murine factor-dependent cell Patersen-erythropoietin receptor (FDCP-EpoR) cells harboring human wild-type or V617F JAK2 resulted in inhibition of cell proliferation with a 50% inhibitory concentration (IC(50)) of 2.1 microM and 0.25 microM, respectively. Moreover, CP-690,550 induced a significant pro-apoptotic effect on murine FDCP-EpoR cells carrying JAK2(V617F), whereas a lesser effect was observed for cells carrying wild-type JAK2. This activity was coupled with inhibition of phosphorylation of the key JAK2(V617F)-dependent downstream signaling effectors signal transducer and activator of transcription (STAT)3, STAT5, and v-akt murine thymoma viral oncogene homolog (AKT). Furthermore, CP-690,550 treatment of ex-vivo-expanded erythroid progenitors from JAK2(V617F)-positive PV patients resulted in specific, antiproliferative (IC(50) = 0.2 microM) and pro-apoptotic activity. In contrast, expanded progenitors from healthy controls were less sensitive to CP-690,550 in proliferation (IC(50) > 1.0 microM), and apoptosis assays. The antiproliferative effect on expanded patient progenitors was paralleled by a decrease in JAK2(V617F) mutant allele frequency, particularly in a patient homozygous for JAK2(V617F). Flow cytometric analysis of expanded PV progenitor cells treated with CP-690,550 suggests a possible transition towards a pattern of erythroid differentiation resembling expanded cells from normal healthy controls.

Polycythemia vera is not initiated by JAK2V617F mutation

OBJECTIVE

The somatic JAK2(V617F) mutation is seen in most polycythemia vera (PV) patients; however, it is not clear if JAK2(V617F) is the PV-initiating mutation.

METHODS

In order to examine this issue, we developed a novel real-time quantitative allele-specific PCR, in which allelic discrimination is enhanced by the synergistic effect of a mismatch in the -1 position, and a locked nucleic acid (LNA) nucleoside at the -2 position.

RESULTS

Determination of allelic frequencies was reproducible (SD = 1.5%) and sensitive--0.1% mutant allele detected in 40 ng of DNA. The JAK2(V617F) frequency in clonal granulocytes from 3 PV females was less than 50% (27.5 +/- 11) and in 7 females greater than 50% (75 +/- 10.5). We also found that wild-type JAK2 BFU-E colonies from PV patients can grow without erythropoietin. The identification of the primary genetic lesion resulting in PV is essential for the development of novel therapeutic strategies.

CONCLUSION

Our studies correlating the frequency of JAK2(V617F) mutant allele and clonality, as well as the presence of homozygous wild-type JAK2 erythropoietin-independent erythroid colonies, provide compelling evidence that the JAK2(V617F) is not the PV-initiating mutation. This supports a model wherein the JAK2(V617F) mutation arises as a secondary genetic event. Furthermore, our results indicate that an undefined molecular lesion, preceding JAK2(V617F), is responsible for clonal hematopoiesis in PV. We conclude that development of therapeutic strategies that target the JAK2(V617F) clonal cells may not be sufficient for eradication of PV.

A novel mutation of the cytochrome-b5 reductase gene in an Indian patient: the molecular basis of type I methemoglobinemia

We report here a novel mutation in the cytochrome b5 reductase gene resulting in type I methemoglobinemia. A single T->C transition in exon 8 at position 25985 was identified, changing codon 217 from Leu to Pro (L217P). The mutation is located in the NADH binding domain at the base of alpha-helix Nalpha3, a region of sequence highly conserved from yeast to man. A quantitative assessment of the thermodynamic cost of this mutation at 37 degrees C revealed a ten-fold drop in the free energy of stability. Alterations in hydrogen bonding and solvent accessibility surrounding residue 217 were predicted based on computer modeling.

Differential modulation of murine host immune response by salivary gland extracts from the mosquitoes Aedes aegypti and Culex quinquefasciatus

Mosquitoes (Diptera: Culicidae) are major vectors of numerous infectious agents. Compounds in mosquito saliva not only facilitate blood-feeding, but may also have an impact upon the immune system of vertebrate hosts. Consequently, the exposure to mosquito saliva may influence pathogen transmission, establishment and disease development. Using two medically important vector mosquitoes, Aedes aegypti (L.) and Culex quinquefasciatus Say, we examined the effects of mosquito saliva on immune cells of host mice. After antigen-specific or non-specific stimulation, murine splenocyte proliferation and production of both Th1 and Th2 cytokines were significantly reduced in the presence of salivary gland extract (SGE) from Ae. aegypti, but not SGE from Cx. quinquefasciatus. T cell populations were highly susceptible to this suppression, showing increased mortality and reduced division rates - judged by flow cytometric analyses. Evidently these two culicine mosquitoes differ in their host immunomodulatory activities.

Lipid transfer from insect fat body to lipophorin: comparison between a mosquito triacylglycerol-rich lipophorin and a sphinx moth diacylglycerol-rich lipophorin

Two insect lipoproteins, triacylglycerol-rich Aedes aegypti lipophorin and diacylglycerol-rich Manduca sexta lipophorin, were compared in their ability to load neutral lipid from fat body. When fat body of M. sexta was incubated in vitro with [3H]oleic acid, all radiolabeled fatty acids were esterified, predominantly to triacylglycerol. In A. aegypti fat body, however, half of the label remained as free fatty acids. When A. aegypti fat body was radiolabeled with [3H]glycerol, most of the radiolabel was incorporated in triacylglycerol. When either A. aegypti or M. sexta lipophorin was incubated with A. aegypti fat body, labeled with [3H]oleic acid, both lipophorins incorporated mainly radiolabeled free fatty acids, while almost no radiolabeled glycerides were transferred. When the same experiment was performed with A. aegypti fat body, radiolabeled with [3H]glycerol, very little transfer of radiolabeled glycerides was detected. In contrast, when either M. sexta or A. aegypti lipophorin was incubated with M. sexta fat body, both lipophorins incorporated neutral lipids, predominantly diacyglycerol. A. aegypti lipophorin incorporated half the amount of radiolabeled lipid, compared to M. sexta lipophorin. Lipophorins from both species were treated with triacylglycerol lipase of the yeast Candida cylindracea. Although this lipase readily delipidated M. sexta HDLp, it was not able to remove triacylglycerol from A. aegypti HDLp. The data presented suggest that, under the conditions used, lipid transfer from fat body to lipophorin in A. aegypti is not as efficient as in M. sexta.

A heme-binding protein from hemolymph and oocytes of the blood-sucking insect, Rhodnius prolixus. Isolation and characterization

A heme-binding protein has been isolated and characterized from both the hemolymph and oocytes of the blood-sucking insect, Rhodnius prolixus. The protein from both sources is identical in most aspects studied. The Rhodnius heme-binding protein (RHBP) is composed of a single 15-kDa polypeptide chain coiled in a highly alpha-helical structure which binds non-covalently one heme/polypeptide chain. This RHBP is not produced by limited degradation of hemoglobin from the vertebrate host, since specific polyclonal antibodies against it do not cross-react with rabbit hemoglobin, and since it differs from hemoglobin in having a distinct amino-acid composition and NH2-terminal sequence. The spectrum of the dithionite-reduced protein has peaks at 426, 530, and 559 nm and resembles that of a b-type cytochrome. RHBP from hemolymph is not saturated with heme and promptly binds heme added to the solution. The oocyte protein, on the other hand, is fully saturated and is not capable of binding additional heme.

Nitric oxide loading of the salivary nitric-oxide-carrying hemoproteins (nitrophorins) in the blood-sucking bug Rhodnius prolixus

The salivary glands of the blood-sucking bug Rhodnius prolixus are formed by a single layer of binucleated epithelial cells surrounded by a double layer of transversely oriented smooth muscle cells. The epithelial cells are rich in rough endoplasmic reticulum and mitochondria and have abundant microvillar projections towards the gland lumen. This cell layer surrounds a relatively large cavity where abundant secretory material is stored. Epithelial cells produce an intense and generalized NADPH diaphorase reaction, in contrast to other tissues such as brain, Malpighian tubules and skeletal muscle. Ultrastructural analysis of the osmiophilic reaction product indicates that it is localized within cytoplasmic vacuoles, a similar location to that of NADPH diaphorase (NO synthetase) activity in neuronal cells of vertebrates. Measurements of the time course of protein accumulation, NADPH diaphorase activity and the degree of nitrosylation of hemoproteins (nitrophorins) in the salivary glands of Rhodnius prolixus nymphs after a blood meal indicate that the nitrophorins are synthesized and accumulate when NO production is low (with a 25% loading of the nitrophorins during the fourth- to fifth-instar molt). NO loading of the nitrophorins increases to 90% after the molt, concomitant with a large increase in the salivary NADPH diaphorase activity. It is concluded that synthesis of NO occurs within the epithelial cells while the nitrophorins are stored extracellularly. It is hypothesized that the luminally oriented microvilli may serve as a diffusion bridge to direct intracellularly produced NO into the luminal cavity, where the nitrophorins are stored.

Purification, partial characterization, and cloning of nitric oxide-carrying heme proteins (nitrophorins) from salivary glands of the blood-sucking insect Rhodnius prolixus

Four nitric oxide (NO)-carrying proteins have been isolated from salivary glands of the blood-sucking insect Rhodnius prolixus. These have been given the collective name "nitrophorins," and individual proteins are designated NP1-NP4 in order of their relative abundance in the glands. All four reversibly bind NO; spectral shifts associated with NO binding indicate the interaction of NO with an Fe(III) heme. Physical properties, amino acid composition, and amino-terminal sequences of the nitrophorins are reported. The most abundant nitrophorin was cloned, and its sequence was determined.

Salivary vasodilators of Aedes triseriatus and Anopheles gambiae (Diptera: Culicidae)

Salivary vasodilators of Aedes aegypti (L.) and Anopheles albimanus (Wiedemann) were characterized previously as a tachykinin peptide and a catechol oxidase/peroxidase activity, respectively. To verify whether these two different vasodilators also were found in other distantly related members of each mosquito genus, we characterized the vasodilators from A. triseriatus and A. gambiae. A. triseriatus salivary gland homogenates produced a reversible, endothelium dependent vasorelaxation of rabbit aortic rings constricted with norepinephrine, and contracted an isolated guinea pig ileum preparation. Additionally, the homogenate had no activity on both smooth muscle preparations when both tissues were desensitized previously by a large dose of substance P. Taken together, these assays suggest the presence of a salivary tachykinin in A. triseriatus. A. gambiae salivary gland homogenates induced a slow vasodilation on both endothelium intact and endotheliumless preparations of aortic rings. A. gambiae homogenates also displayed catechol oxidase and peroxidase activity against o-dianisidine but not against serotonin, indicating the presence of an enzyme system slightly different from A. albimanus. We conclude that the presence of salivary tachykinins or catechol/oxidase is not unique to A. aegypti or A. albimanus.

Nitric oxide synthase activity from a hematophagous insect salivary gland

The salivary glands of the hematophagous insect, Rhodnius prolixus, contain a nitrosylhemeprotein that dissociates its ligand, NO, to the host tissues while the insect is searching for a blood meal. We now report a salivary nitric oxide synthase activity in this insect. The activity is dependent on NADPH, FAD, tetrahydrobiopterin, calmodulin, Ca2+, and converts arginine to citrulline while producing vasorelaxing activity. Molecular sieving indicates a molecular weight of 185 kDa, coeluting with a diaphorase activity. Results indicate similarity of this insect activity to the vertebrate constitutive NO synthase, suggesting NO synthesis is an evolutionary old biological pathway.

The salivary catechol oxidase/peroxidase activities of the mosquito Anopheles albimanus

Salivary gland homogenates from adult female Anopheles albimanus mosquitoes relaxed aortic rings preconstricted with noradrenaline (NA). This relaxation is slow and is due to destruction of NA. Incubation of NA with the homogenate yielded a product with a spectrum consistent with the corresponding adrenochrome. Oxidation of NA was enhanced by a superoxide generation system and inhibited by the combined action of superoxide dismutase and catalase. Additionally, peroxidase activity on both synthetic (o-dianisidine) and biologically active (serotonin) substrates was also present in the salivary gland homogenates, this latter activity requiring hydrogen peroxide. Noradrenaline oxidation, serotonin and o-dianisidine peroxidation and vasodilation all co-elute with a heme protein of relative molecular mass 50,000, as determined by molecular sieving chromatography. Peroxidase activity was localized in the posterior (female-specific) lobes of salivary glands and was also detected in nitrocellulose membranes probed by hungry mosquitoes. Protein and peroxidase activities were significantly lower in salivary glands of mosquitoes after probing and feeding on blood. It is suggested that adult female Anopheles albimanus mosquitoes contain a salivary heme peroxidase that functions during blood finding and blood feeding by destroying hemostatically active biogenic amines released by the vertebrate host during tissue destruction.

Reversible binding of nitric oxide by a salivary heme protein from a bloodsucking insect

The bloodsucking bug Rhodnius prolixus has a salivary vasodilator, previously characterized as a nitrovasodilator, with salivary smooth muscle-relaxing and antiplatelet activity. Rhodnius salivary glands are bright red owing to the abundance of heme proteins. Electron paramagnetic resonance and optical spectroscopic experiments indicated that the salivary vasodilator is a nitrosylheme protein with an Fe(III) heme that binds nitric oxide (NO) reversibly. Dilution of the protein in neutral pH promoted NO release. This protein thus appears to be the NO carrier that helps R. prolixus to feed on blood.