MinimuMM-seq: Genome Sequencing of Circulating Tumor Cells for Minimally Invasive Molecular Characterization of Multiple Myeloma Pathology

Multiple myeloma (MM) develops from well-defined precursor stages; however, invasive bone marrow (BM) biopsy limits screening and monitoring strategies for patients. We enumerated circulating tumor cells (CTC) from 261 patients (84 monoclonal gammopathy of undetermined significance, 155 smoldering multiple myeloma, and 22 MM), with neoplastic cells detected in 84%. We developed a novel approach, MinimuMM-seq, which enables the detection of translocations and copy-number abnormalities through whole-genome sequencing of highly pure CTCs. Application to CTCs in a cohort of 51 patients, 24 with paired BM, was able to detect 100% of clinically reported BM biopsy events and could replace molecular cytogenetics for diagnostic yield and risk classification. Longitudinal sampling of CTCs in 8 patients revealed major clones could be tracked in the blood, with clonal evolution and shifting dynamics of subclones over time. Our findings provide proof of concept that CTC detection and genomic profiling could be used clinically for monitoring and managing disease in MM.

SIGNIFICANCE

In this study, we established an approach enabling the enumeration and sequencing of CTCs to replace standard molecular cytogenetics. CTCs harbored the same pathognomonic MM abnormalities as BM plasma cells. Longitudinal sampling of serial CTCs was able to track clonal dynamics over time and detect the emergence of high-risk genetic subclones. This article is highlighted in the In This Issue feature, p. 247.

Abstract 3582: Single-cell RNA-sequencing for immune profiling of SARS-CoV2 vaccine response in healthy individuals and patients with precursor plasma cell malignancies

Introduction: Patients with hematological malignancies exhibit inferior response to SARS-CoV2 vaccination, compared to healthy individuals, however little is known about patients with precursor hematological malignancies and the cellular underpinnings of vaccination response. Monoclonal Gammopathy of Undetermined Significance (MGUS) and Smoldering Myeloma (SMM) are plasma cell premalignancies that precede Multiple Myeloma (MM) and exhibit signs of immune dysregulation; they affect approximately 5% of the population over 50 years of age, who remain largely undiagnosed, due to lack of screening. In November 2019, we launched the IMPACT study to characterize the immune response to SARS-CoV2 vaccination in patients with plasma cell dyscrasias and healthy individuals.

Methods: We performed single-cell RNA-sequencing on 224 peripheral blood mononuclear cell samples drawn from 118 IMPACT (IRB #20-332) participants with MGUS (n=20), SMM (n=48), or MM (n=24), as well as healthy individuals (n=26). Samples were collected before vaccination and after 2 doses of BNT162b2 (Pfizer-BioNtech) (n=123), mRNA-1273 (Moderna) (n=83) or 1 dose of Ad26.COV2.S (Janssen) (n=14).

Results: Overall, we sequenced 2,025,611 cells from 224 samples of 118 patients with MGUS, SMM, MM and healthy individuals pre- and post-vaccination for SARS-CoV2, and profiled 553,082 T-cells, 95,392 B-cells, 74,394 NK cells, 195,371 Monocytes, and 35,236 Dendritic cells (DC). We identified activated clusters of B-cells, NK cells and DCs expressing genes such as CD83, CD69, CXCR4, and genes related to the NF-kB and AP-1 pathways. We compared cell type abundances pre- and post-vaccination within each participant population and found that activated CD83+ cells significantly increased post-vaccination in healthy individuals and patients with MGUS (paired t-test, q < 0.1), but not in patients with SMM or overt MM. At baseline, patients with SMM and MM had significantly fewer memory B-cells and significantly more cytotoxic T-cells and NK cells, compared to healthy individuals (Wilcoxon, q < 0.1), which could partly explain the differences observed post-vaccination. Patients with MM also had significantly higher levels of tolerogenic IL-10-expressing DCs (DC10) at baseline (Wilcoxon, q < 0.1), which could be dampening antigen-specific T-cell responses.

Conclusion: We identified a significant expansion of activated B-cell, NK cell and DC subpopulations expressing CD83, CD69 and CXCR4, following vaccination in healthy individuals and patients with MGUS, but less so in patients with SMM and overt MM. Our results provide insight into the cellular mechanisms of immune response to SARS-CoV2 vaccination in healthy individuals and patients with precursor plasma cell malignancies and suggest that asymptomatic individuals with SMM may exhibit inferior response to vaccination.

Citation Format: Romanos Sklavenitis-Pistofidis, Yoshinobu Konishi, Michelle Aranha, Mahshid Rahmat, Ting Wu, Michael Timonian, Shohreh Varmeh, Daniel Heilpern-Mallory, Michael P. Agius, Nang K. Su, Elizabeth D. Lightbody, Jacqueline Perry, Erica M. Horowitz, Anna V. Justis, Daniel Auclair, Catherine R. Marinac, Eric S. Fischer, Gad Getz, Irene M. Ghobrial. Single-cell RNA-sequencing for immune profiling of SARS-CoV2 vaccine response in healthy individuals and patients with precursor plasma cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3582.

Abstract 640: Genome sequencing of circulating multiple myeloma cells for minimally invasive molecular characterization of precursor disease pathology

Introduction: Multiple myeloma (MM) develops from indolent stages monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Precursor conditions are incidentally diagnosed and require invasive bone marrow (BM) biopsies for complete characterization, highlighting the urgent need for improved early detection methods. Minimally invasive blood biopsies to measure circulating multiple myeloma cells (CMMCs) as markers of MM disease development are a promising solution to this unmet need. Here, we present our novel method CatchTheFISH, for whole genome sequencing (WGS) of CMMCs that enables genomic profiling and WGS based cytogenetic analyses from enriched liquid biopsy samples. Application of WGS in a cohort of 20 patients, revealed CMMCs were of tumor origin and able to faithfully match BM sequencing results and detect 100% of clinically reported events.

Methods: Peripheral blood from 110 SMM patients from the PCROWD observational study (Dana-Farber Cancer Institute IRB #14-174) was collected and processed on CellSearch system (Menarini Silicon Biosystems), with enrichment and enumeration of CMMCs based on CD138+38+CD45-19- immunophenotype. In 20 patients, CMMCs and white blood cells were sorted for library construction, quantification and WGS on Illumina NovaSeq6000. Mutation analyses were performed with the cancer genome analysis pipelines of the Broad Institute.

Results: CMMCs were detected in 84% of SMM patients enrolled in the study, with a median count of 13 CMMCs (range 0 to 43836). We first demonstrated the concordance of WGS results obtained from CMMCs with BM. In 100% of patients tested with paired BM and CMMCs (n = 8), we observed full agreement in structural event calling between our samples and clinical reports, including translocations and CNAs (trisomies, tetrasomy, monosomy 13 and 1q gain/amplification). Next, we showed WGS of CMMCs provided increased diagnostic yield compared to BM biopsy for the detection of structural events and MM-associated driver mutations. In 7 patients (88%) we detected additional aberrations not found by FISH. Unknown translocation events of IGH-MYC and t(14;20) were distinguished in two patients. Additionally, our method enabled detection of MM driver mutations. Three patients (38%) were found to harbor RAS mutations (KRAS and NRAS) in BM samples, which were also validated in matched CMMCs. Finally, we assessed a validation cohort of 12 SMM patients with CMMCs only. WGS detected comprehensive mutation data across all scales including clinically relevant translocations, trisomies, CNAs and mutations.

Conclusion: Our findings provide proof of principle that capture and genomic profiling of CMMCs could be a robust surrogate to BM biopsy, allowing minimally invasive detection and monitoring of disease, unlocking the clinical potential of liquid biopsies for MM diagnostics.

Citation Format: Ankit K. Dutta, Jean-Baptiste Alberge, Elizabeth D. Lightbody, Romanos Sklavenitis-Pistofidis, Cody J. Boehner, Tarek H. Mouhieddine, Anna Cowan, Nang Kham Su, Erica M. Horowitz, Andrew Dunford, Chip Stewart, Ziao Lin, Laura Hevenor, Hadley Barr, Amanda Cao, Ornkleaw Zepp, Thai Bui, Steve Gross, Daniel Auclair, Gad Getz, Irene M. Ghobrial. Genome sequencing of circulating multiple myeloma cells for minimally invasive molecular characterization of precursor disease pathology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 640.

Physician-derived asthma diagnoses made on the basis of questionnaire data are in good agreement with interview-based diagnoses and are not affected by objective tests

BACKGROUND

Defining the phenotype is critical for investigating the genetic etiology of asthma. As part of the Collaborative Study on the Genetics of Asthma (CSGA), the primary objective of which is to identify asthma susceptibility loci, an algorithm was designed to determine diagnoses of definite asthma, probable asthma, less than probable asthma, or no asthma. A respiratory questionnaire was designed to assist in the process of characterizing the asthma phenotype.

OBJECTIVE

This study was designed to determine the validity of the CSGA algorithm for the diagnosis of asthma, to determine agreement in assessing an asthma diagnosis between the information obtained by the CSGA questionnaire versus a patient interview by a panel of specialist physicians, and to determine the degree to which objective tests would alter the questionnaire-based certainty of asthma diagnosis.

METHODS

An expert panel of asthma clinicians (n = 4) indicated to what degree they were certain that a subject (n = 48) had asthma as determined by using a 6-point Likert scale based on a 20-minute interview (phase I), a review of the CSGA questionnaire (phase II), a review of the questionnaire plus skin test and peripheral blood eosinophilia data (phase III), and a review of phase III information plus pulmonary data (spirometry and methacholine-reversibility testing; IV). Intraclass correlation coefficients (ICCs) were calculated between the physicians' interpretation of the likelihood of asthma based on the information they received during each of the phases and between the CSGA algorithm and each of the phases.

RESULTS

Interjudge reliability with regard to the degree of certainty with which an asthma diagnosis could be made by interview was excellent (ICC, 98; 95% confidence intervals [95% CIs], 0.87-0.99). We also found that the agreement between the physicians' interview with the patients (phase I) and the CSGA algorithm was good and at least as good with the addition of the CSGA questionnaire data and objective data (ICC, 0. 65-0.75). Good agreement was also observed between the average certainty score from the interview and the CSGA questionnaire (ICC, 92; 95% CI, 0.76-0.93), and ICCs determining the agreement on asthma diagnosis between phase I and phases III and IV, in which objective data were introduced, did not change from the ICCs comparing phase I with phase II (ICC of 0.93 [95% CI, 0.79-0.96] and ICC of 0.91 [95% CI 0.73-0.95], respectively).

CONCLUSION

We conclude that the CSGA algorithm is a valid tool for which the diagnosis of asthma can be made at an acceptable level of certainty and that the CSGA questionnaire, interpreted by an asthma specialist, is a useful tool for the diagnosis of asthma in clinical or epidemiologic studies.

Substance P activates the release of histamine from human skin mast cells through a pertussis toxin-sensitive and protein kinase C-dependent mechanism

Using pharmacologic agents, we explored the mechanism by which a potent neuropeptide, substance P, induces the secretion of histamine from human skin mast cells and compared their effects on substance P-induced histamine release to the secretion activated by anti-IgE. Histamine release from human cutaneous mast cells induced by substance P was inhibited by the Ge-protein inhibitor pertussis toxin that, in turn, did not affect the IgE-mediated secretion. Similarly to anti-IgE, two activators of protein kinase C, tetradecanoylphorbol acetate (TPA) and bryostatin 1, significantly inhibited the substance P-induced response. In contrast, drugs that enhance intracellular levels of cAMP, an inhibitor of protein kinases, genistein, and a protease inhibitor, AEBSF, did not affect substance P-induced histamine secretion, whereas these compounds significantly reduced the response initiated by anti-IgE. Our data demonstrate that substance P activates human cutaneous mast cells by acting on G proteins and protein kinase C. Our results also suggest that the biochemical pathways underlying mast cell activation by substance P and anti-IgE are to a great extent unrelated.

Histamine release from human basophils induced by platelet activating factor: the role of extracellular calcium, interleukin-3, and granulocyte-macrophage colony-stimulating factor

Although we have demonstrated that platelet activating factor (PAF) directly induces histamine release from human basophils, other studies have failed to report similar effects. In an attempt to understand the variability of these results, we examined the effect of some factors that could influence the basophils' response to PAF such as, extracellular Ca2+ and cytokines (interleukin-3 and granulocyte-macrophage colony-stimulating factor [GM-CSF]). The secretion of histamine induced by PAF was optimal when the cells were incubated in Ca2+ for 2 to 5 minutes, whereas it declined at longer time intervals up to 15 minutes. If cytochalasin B (5 micrograms/ml) was coincubated with PAF (1 mumol/L) to enhance the secretory response, histamine release was maximal at time 0 and decreased in parallel with the time of the basophils' exposure to Ca2+, like 0.1 microgram/ml anti-IgE-induced histamine secretion but unlike 1 mumol/L formyl-methionyl-leucyl-phenylalanine-induced histamine secretion. We found that there is synergy between interleukin-3 (1 to 3 ng/ml) and PAF (1 mumol/L) for secretion of histamine from human basophils (p < 0.05) and that GM-CSF (10 ng/ml) significantly (p < 0.02) potentiates the secretion of histamine activated by PAF (1 mumol/L). Our results demonstrate that: (1) the kinetics of the interaction between Ca2+ and the activation pathway that leads to histamine secretion are central events in the release reaction elicited by PAF in human basophils, and (2) interleukin-3 and GM-CSF can potentiate the secretory response of human basophils stimulated by PAF.

Studies of the intracellular Ca2+ levels in human adult skin mast cells activated by the ligand for the human c-kit receptor and anti-IgE

The human c-kit receptor ligand, rhSCF, is the only cytokine known to be active on human mast cells, but its intracellular signal transduction pathway is still unknown. We compared the effect of rhSCF on intracellular Ca2+ levels in purified (> 70% pure) adult skin mast cells with two other immunologic stimuli, namely, anti-IgE and substance P. Both rhSCF (1 microgram/mL) and anti-IgE (3 micrograms/mL) induced a rapid (< 20 sec) and sustained (T1/2 for decay > 10 min) increase in free cytosolic Ca2+ concentration. In contrast, substance P (5 microM) elicited a very rapid (< 1 sec) and transient (T1/2 for decay congruent to 5 sec) rise in intracellular Ca2+ levels. Intracellular cAMP levels were then increased by pharmacologic means to examine the role of the cyclic nucleotide in controlling the Ca2+ response in skin mast cells. A combination of the general phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX) (200 microM) and the adenylate cyclase activator, forskolin (30 microM) was effective in inhibiting the Ca2+ response induced by rhSCF or anti-IgE (82 and 68% inhibition, respectively), while IBMX and forskolin alone were much less effective. The phosphodiesterase isozyme IV inhibitor, rolipram (10 microM), variably affected the increase in Ca2+ levels induced by anti-IgE, but it exerted a significant inhibitory activity on anti-IgE- or rhSCF-induced response in the presence of forskolin (30 micrograms/mL) (33 and 67%, respectively). Two different protein kinase C (PKC) activators TPA (200 nM) and bryostatin 1 (200 nM) similarly inhibited rhSCF- (22 and 32%, respectively) and anti-IgE-induced (24 and 32%) Ca2+ response. Finally, the kinase inhibitor genistein (30 micrograms/mL) was a somewhat more effective inhibitor of the rise in intracellular Ca2+ induced by rhSCF (100%) than that activated by anti-IgE (54%) (P < 0.05). These data indicate that rhSCF and anti-IgE may act on human mast cells through a common pathway to increase free cytosolic Ca2+ levels and this effect is similarly modulated by various drugs.

A comparative study of the effects of 1-acyl-2-acetyl-sn-glycero-3-phosphocholine and platelet activating factor on histamine and leukotriene C4 release from human leukocytes

BACKGROUND

IgE-mediated stimulation of human basophils and lung mast cells causes the synthesis of larger amounts of 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (1-acyl-2-acetyl-GPC) than 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor [PAF]).

METHODS

To study the biologic activity of 1-acyl-2-acetyl-GPC, we compared its effects and those of PAF on histamine and leukotriene C4 (LTC4) release from human mixed leukocytes that contained basophils.

RESULTS

1-Acyl-2-acetyl-GPC (0.1 to 10 mumol/L) failed to release significant amounts of histamine (> or = 10%) in most donors tested (20 of 24), whereas PAF (0.01 to 1 mumol/L) was active in 58%. 1-Acyl-2-acetyl-GPC (0.1 to 10 mumol/L) was a stimulus for LTC4 release (132 +/- 30 ng/micrograms of histamine) with a potency of about 1000 times less than PAF. The kinetics of 1-acyl-2-acetyl-GPC-activated LTC4 release were similar to those of PAF (half-life approximately equal to 2 minutes). The specific PAF receptor antagonist, WEB 2086 (10 nmol/L to 10 mumol/L), inhibited both 1-acyl-2-acetyl-GPC- and PAF-mediated LTC4 release with the same potency (inhibitory concentration of 50% approximately equal to 1.5 mumol/L). Brief (2-minute) cell preincubation with 1-acyl-2-acetyl-GPC in the absence of extracellular Ca2+ induced a decrease in the subsequent Ca2+ dependent activation of PAF. Similarly, 1-acyl-2-acetyl-GPC (0.1 to 10 mumol/L) caused a concentration-dependent inhibition of PAF-activated histamine secretion (inhibitory concentration of 50% approximately equal to 0.2 mumol/L).

CONCLUSIONS

Our data suggest that 1-acyl-2-acetyl-GPC may represent, under certain circumstances, a modulator of human basophil mediator release via mechanisms shared with PAF.

Pharmacologic control of histamine release from human basophils induced by platelet-activating factor

We studied the effect of several compounds that influence different cell activation steps on platelet-activating factor (PAF)-induced basophil histamine secretion. Isobutylmethylxanthine (1-100 microM), dimaprit (1-100 microM) and dibutyryl adenosine 3',5'-cyclic phosphate (cAMP; 0.01-1 mM), that increase intracellular cAMP levels, concentration-dependently inhibited PAF-elicited histamine release. Rolipram (phosphodiesterase, PDE, isotype IV inhibitor; 0.1 nM-10 microM) potently inhibited histamine secretion activated by PAF, whereas SKF95654 (PDE III inhibitor; 0.01-10 microM) was ineffective. The kinase inhibitor, staurosporine (0.1-100 nM), enhanced PAF-induced basophil histamine release, whereas the G-protein inhibitor, pertussis toxin (1 microgram/ml), had an inhibitory effect. The specific lipoxygenase inhibitor, AA-861 (0.1-10 microM), inhibited PAF-activated histamine release, while the leukotriene A4 hydrolase inhibitor, bestatin (100 microM), had only a marginal effect. Finally, the Ca2+ channel entry blockers, verapamil (3-30 microM) and zinc (1.5-50 microM), inhibited PAF-induced histamine release. These results suggest that PAF is a unique secretagogue for human basophils unlike antigen, anti-IgE or univalent stimuli.

The human recombinant c-kit receptor ligand, rhSCF, induces mediator release from human cutaneous mast cells and enhances IgE-dependent mediator release from both skin mast cells and peripheral blood basophils

The gene product of the steel locus of the mouse represents a growth factor for murine mast cells and a ligand for the c-kit proto-oncogene receptor, a member of the tyrosine kinase receptor class of oncogenes (for review, see O. N. Witte. 1990. Cell 63:5). We have studied the effect of the human recombinant c-kit receptor ligand stem cell factor (rhSCF) on the release of inflammatory mediators from human skin mast cells and peripheral blood basophils and compared its activity to that of rhIL-3, rhSCF (1 ng/ml to 1 microgram/ml) activated the release of histamine and PGD2 from mast cells isolated from human skin. Analysis by digital video microscopy indicated that purified human skin mast cells (84 +/- 5% pure) responded to rhSCF (0.1 to 1 microgram/ml) challenge with a rapid, sustained rise in intracellular Ca2+ levels that was accompanied by secretion of histamine. A brief preincubation (10 min) of mast cells with rhSCF (0.1 pg/ml to 1 ng/ml) significantly enhanced (100 +/- 35%) the release of histamine induced by anti-IgE (3 micrograms/ml), but was much less effective on IgE-mediated release of PGD2. In contrast, a short term incubation with rhSCF did not potentiate the secretion of histamine activated by substance P (5 microM). A 24-h incubation of mast cells with rhSCF did not affect the release of mediators induced by anti-IgE (3 micrograms/ml), probably due to receptor desensitization, rhSCF (1 ng/ml to 3 micrograms/ml) neither caused release of histamine or leukotriene C4 (LTC4) release from leukocytes of 14 donors, nor induced a rise in intracellular Ca2+ levels in purified (greater than 70%) basophils. Brief preincubation (10 min) of leukocytes with rhSCF (1 ng/ml to 3 micrograms/ml) caused an enhancement (69 +/- 11%) of anti-IgE-induced release of histamine that was significant at concentrations as low as 3 ng/ml (p less than 0.05), whereas it appeared less effective in potentiating IgE-mediated LTC4 release. In contrast, a prolonged incubation (24 h) with rhSCF (0.1 pg/ml to 100 ng/ml) did not enhance the release of histamine or LTC4 induced by anti-IgE (0.1 microgram/ml), whereas rhIL-3 (3 ng/ml) significantly potentiated the release of both mediators.(ABSTRACT TRUNCATED AT 400 WORDS)

The human recombinant c-kit receptor ligand, rhSCF, induces mediator release from human cutaneous mast cells and enhances IgE-dependent mediator release from both skin mast cells and peripheral blood basophils

The gene product of the steel locus of the mouse represents a growth factor for murine mast cells and a ligand for the c-kit proto-oncogene receptor, a member of the tyrosine kinase receptor class of oncogenes (for review, see O. N. Witte. 1990. Cell 63:5). We have studied the effect of the human recombinant c-kit receptor ligand stem cell factor (rhSCF) on the release of inflammatory mediators from human skin mast cells and peripheral blood basophils and compared its activity to that of rhIL-3, rhSCF (1 ng/ml to 1 microgram/ml) activated the release of histamine and PGD2 from mast cells isolated from human skin. Analysis by digital video microscopy indicated that purified human skin mast cells (84 +/- 5% pure) responded to rhSCF (0.1 to 1 microgram/ml) challenge with a rapid, sustained rise in intracellular Ca2+ levels that was accompanied by secretion of histamine. A brief preincubation (10 min) of mast cells with rhSCF (0.1 pg/ml to 1 ng/ml) significantly enhanced (100 +/- 35%) the release of histamine induced by anti-IgE (3 micrograms/ml), but was much less effective on IgE-mediated release of PGD2. In contrast, a short term incubation with rhSCF did not potentiate the secretion of histamine activated by substance P (5 microM). A 24-h incubation of mast cells with rhSCF did not affect the release of mediators induced by anti-IgE (3 micrograms/ml), probably due to receptor desensitization, rhSCF (1 ng/ml to 3 micrograms/ml) neither caused release of histamine or leukotriene C4 (LTC4) release from leukocytes of 14 donors, nor induced a rise in intracellular Ca2+ levels in purified (greater than 70%) basophils. Brief preincubation (10 min) of leukocytes with rhSCF (1 ng/ml to 3 micrograms/ml) caused an enhancement (69 +/- 11%) of anti-IgE-induced release of histamine that was significant at concentrations as low as 3 ng/ml (p less than 0.05), whereas it appeared less effective in potentiating IgE-mediated LTC4 release. In contrast, a prolonged incubation (24 h) with rhSCF (0.1 pg/ml to 100 ng/ml) did not enhance the release of histamine or LTC4 induced by anti-IgE (0.1 microgram/ml), whereas rhIL-3 (3 ng/ml) significantly potentiated the release of both mediators.(ABSTRACT TRUNCATED AT 400 WORDS)

Implications of hydronephrosis in the newborn with myelodysplasia

Hydronephrosis has been reported to be present at birth in 6 to 28 per cent of newborns with myelodysplasia. It is unknown whether this hydronephrosis is secondary to abnormal in utero voiding dynamics and is truly present at birth or whether it is acquired postnatally secondary to spinal shock after back closure. We reviewed the perinatal course of 47 myelodysplastic newborns and conclude that the true in utero incidence of hydronephrosis is lower than that suggested in the literature, and that the hydronephrosis seen in many of these newborns is acquired after back closure and is transient in nature.