Recurring germline mosaicism in a family due to reversion of an inherited derivative chromosome 8 from an 8;21 translocation with interstitial telomeric sequences.

BACKGROUND: Mosaicism for chromosomal structural abnormalities, other than marker or ring chromosomes, is rarely inherited. METHODS: We performed cytogenetics studies and breakpoint analyses on a family with transmission of mosaicism for a derivative chromosome 8 (der(8)), resulting from an unbalanced translocation between the long arms of chromosomes 8 and 21 over three generations. RESULTS: The proband and his maternal half-sister had mosaicism for a der(8) cell line leading to trisomy of the distal 21q, and both had Down syndrome phenotypic features. Mosaicism for a cell line with the der(8) and a normal cell line was also detected in a maternal half-cousin. The der(8) was inherited from the maternal grandmother who had four abnormal cell lines containing the der(8), in addition to a normal cell line. One maternal half-aunt had the der(8) and an isodicentric chromosome 21 (idic(21)). Sequencing studies revealed microhomologies at the junctures of the der(8) and idic(21) in the half-aunt, suggesting a replicative mechanism in the rearrangement formation. Furthermore, interstitial telomeric sequences (ITS) were identified in the juncture between chromosomes 8 and 21 in the der(8). CONCLUSION: Mosaicism in the proband, his half-sister and half-cousin resulting from loss of chromosome 21 material from the der(8) appears to be a postzygotic event due to the genomic instability of ITS and associated with selective growth advantage of normal cells. The reversion of the inherited der(8) to a normal chromosome 8 in this family resembles revertant mosaicism of point mutations. We propose that ITS could mediate recurring revertant mosaicism for some constitutional chromosomal structural abnormalities.

Oxidatively modified low-density lipoproteins are potential mediators of proteasome inhibitor resistance in multiple myeloma.

Proteasome inhibitor (PI) therapy has improved the survival of multiple myeloma (MM) patients. However, inevitably, primary or acquired resistance to PIs leads to disease progression; resistance mechanisms are unclear. Obesity is a risk factor for MM mortality. Oxidized LDL (OxLDL), a central mediator of atherosclerosis that is elevated in metabolic syndrome (co-occurrence of obesity, insulin resistance, dyslipidemia and hypertension), has been linked to an increased risk of solid cancers and shown to stimulate pro-oncogenic/survival signaling. We hypothesized that OxLDL is a mediator of chemoresistance and evaluated its effects on MM cell killing by PIs. OxLDL potently suppressed the ability of the boronic acid-based PIs bortezomib (BTZ) and ixazomib, but not the epoxyketone-based PI carfilzomib, to kill human MM cell lines and primary cells. OxLDL suppressed BTZ-induced inhibition of proteasome activity and induction of pro-apoptotic signaling. These cytoprotective effects were abrogated when lipid hydroperoxides (LOOHs) associated with OxLDL were enzymatically reduced. We also demonstrated the presence of OxLDL in the MM bone marrow microenvironment as well as numerous granulocytes and monocytes capable of cell-mediated LDL oxidation through myeloperoxidase. Our findings suggest that OxLDL may be a potent mediator of boronic acid-based PI resistance, particularly for MM patients with metabolic syndrome, given their elevated systemic levels of OxLDL. LDL cholesterol-lowering therapy to reduce circulating OxLDL, and pharmacologic targeting of LOOH levels or resistance pathways induced by the modified lipoprotein, could deepen the response to these important agents and offer clinical benefit to MM patients with metabolic syndrome.

Acute multilineage (B/myeloid) leukemia with RUNX1 duplication/amplification and hypereosinophilia.

A 14-year-old girl presented with myalgias and decreased energy and was found to have a white count of 73,000 with 75% eosinophils. Flow cytometry and immunostains showed the blasts in the bone marrow expressed both myeloid and lymphoid markers. Patient was diagnosed with acute multilineage (B/Myeloid) leukemia. Genetic testing revealed four copies of the RUNX1 gene region in 25.5%, with a normal karyotype and no evidence of t(8;21) or t(12;21) by fluorescence in situ hybridization. RUNX1 translocations and amplifications have been implicated in acute myeloblastic leukemia, acute lymphoblastic leukemia, and MDS, but have not yet been seen with acute multilineage leukemia. Additionally, it is unclear what the risk stratification of this unique presentation will turn out to be.

PML-RARA fusion resulting from a cryptic insertion of RARA gene into PML gene without the reciprocal RARA-PML fusion: clinical, cytogenetic, and molecular characterization and prognosis.

We describe a case of acute promyelocytic leukemia in a 61-yr-old woman with a cryptic insertion of RARA gene into PML gene. Using a combination of cytogenetic and molecular methods, we confirmed the insertion and presence of the PML-RARA transcript and lack of the reciprocal RARA-PML transcript. Although such cryptic insertions leading to a PML-RARA fusion have been previously reported, we show that such variant insertions, based on our case, appear to have the same prognostic significance as the classical t(15;17)(q22;q21).

Complex/variant translocations in chronic myelogenous leukemia (CML): genesis and prognosis with 4 new cases.

In 5-10% of cases with CML, variant or complex translocations (CT) are seen that may result in atypical fluorescence in situ hybridization signal patterns. Dual color, dual fusion fluorescence in situ hybridization (D-FISH) patterns are instrumental in identifying the genesis of these CT, but their prognostic implications remain controversial. The most common mechanism is a two-step process in which a standard two-way translocation (9;22) is followed by subsequent rearrangements involving other chromosomes. The second common mechanism is the one-step process wherein breakage occurs simultaneously on different chromosomes leading to CT. The typical D-FISH pattern seen with the one-step mechanism is 1F2G2R, while the pattern for the two-step mechanism can be variable (2F1G1R, 1F1G1R, 1F1G2R, 1F2G1R, etc.). We have studied 4 cases of CT using metaphase FISH with triple color, dual fusion ASS1, ABL1 and BCR probes to understand the genesis of these CT. All the patients were treated with imatinib, but only patients 3 and 4 showed remission. Our results indicate that the CT in cases 1, 3 and 4 arose from a one-step mechanism and case 2 from a multi-step mechanism. Response to imatinib varied from full remission to no response. Long term follow-up is necessary to evaluate the prognostic implications of these CT.

Conventional Cytogenetic Analysis of Constitutional Abnormalities: A 20-Year Review of Proficiency Test Results From the College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee.

CONTEXT.­: The joint College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee works to ensure competency and proficiency of clinical cytogenetics testing laboratories through proficiency testing programs for various clinical tests offered by such laboratories, including the evaluation of constitutional abnormalities. OBJECTIVE.­: To review and analyze 20 years of constitutional chromosome analysis proficiency testing results (2003-2022), primarily utilizing G-banded karyograms. DESIGN.­: A retrospective review of results from 2003 through 2022 was performed, identifying challenges addressing constitutional disorders. The chromosomal abnormalities and overall performance were evaluated. RESULTS.­: A total of 184 cases from 161 proficiency testing challenges were administered from 2003 through 2022. Challenges consisted of metaphase images and accompanying clinical history for evaluation of numerical and/or structural abnormalities. Of the 184 cases, only 2 (1%) failed to reach an 80% grading consensus for recognition of the abnormality. Both cases illustrated the limitations of correctly characterizing some chromosomal abnormalities, including recombinant chromosomal abnormalities and isochromosome identification. In addition, 2 cases failed to reach a consensus for nomenclature reporting: 1 with an isochromosome and another with a duplication. CONCLUSIONS.­: This 20-year review illustrates the high rate of competency and proficiency of cytogenetic laboratories in the correct identification of constitutional chromosome abnormalities.

Cytogenetic abnormalities precede morphological abnormalities in developing malignant conditions: report of 2 cases.

We previously hypothesized that cytogenetic abnormalities precede morphological abnormalities in developing malignant conditions. In this context we evaluated additional cases to further confirm that hypothesis. We report on 2 additional cases in which clonal cytogenetic abnormalities were observed in otherwise morphologically normal samples. Case 1 is a bone marrow from a 73 year old male with transformed follicular lymphoma (FL), while case 2 is a lymph node from a 53-year-old with lymphadenopathy, both referred to the cytogenetics laboratory for evaluation. A 73-year-old male presented with an enlarging left inguinal mass surrounding and obliterating the left iliac vein. A tissue core biopsy of the mass revealed recurrent high grade FL with diffuse large B-cell lymphoma (DLBCL). Examination of a random bone marrow biopsy of the adjacent left posterior iliac crest showed only mild hypercellularity (50%) and no evidence of malignancy, and the results were confirmed by flow cytometry. Cytogenetic evaluation revealed an interstitial deletion, del (9)(q13q32). In case 2, morphologically the lymph node showed extensive paracortical hyperplasia with numerous eosinophils and no clear indication of a neoplastic process with no abnormal lymphoid population observed by flow. PCR studies for TCR gamma and IgH gene rearrangements were negative for clonality. Chromosome analysis demonstrated 47,XY,+add(1)(p22),t(3;14)(q27;q11.2)[13]/46,XY[7]. FISH studies showed a BCL6 gene rearrangement but no TCRAD rearrangement. A subsequent inguinal lymph node biopsy showed DLBCL. These cases along with the other cases in the literature provide further evidence of genetic abnormalities preceding morphological abnormalities in developing malignant conditions.

Myeloid/Lymphoid Neoplasm with FGFR1 Rearrangement Presenting with Polycythemia Vera and T-cell Acute Lymphoblastic Leukemia.

Myeloid/lymphoid neoplasm with fibroblast growth factor 1 rearrangements (MLN-FGFR1) represents a rare group of hematologic neoplasms, with approximately 100 cases reported to date. A 69-year-old woman with a history of polycythemia and leukocytosis, with negative molecular testing for JAK2, CALR, and MPL, presented with diffuse adenopathy. A lymph node (LN) biopsy revealed effacement by T-lymphoblasts, consistent with T-cell acute lymphoblastic lymphoma (T-ALL). A staging bone marrow (BM) biopsy demonstrated trilineage hyperplasia, which, taken together with the patient's elevated hemoglobin and low serum erythropoietin level, fulfilled diagnostic criteria for polycythemia vera. Karyotype and fluorescence in situ hybridization on both the BM and LN demonstrated a FGFR1 rearrangement due to t(8;13), consistent with MLN-FGFR1. Whole genome sequencing on the LN additionally identified a pathogenic frameshift mutation of ASXL1 NC_000020.11:g32434646dup NM_015338.6(ASXL1):c.1934dup p.(Gly646Trpfs) predicted to result in loss of protein function, a finding also observed in 8.1% of BM reads. Both the BM and LN harbored missense variants in HDAC4 NM_001378414.1(HDAC4):c.[2763G>A]; [2763=] p.(Met921Ile) and CHEK2 NM_007194.4(CHEK2):c.[538C>T];[538=] p.(Arg180Cys), with an unknown significance. Despite initial response to Mini-CVD + venetoclax, the patient subsequently experienced rapid clinical deterioration and death. We report the second case of MLN-FGFR1 with an ASXL1 mutation and the first case with HDAC4 and CHEK2 variants.

Phagocytosis-initiated tumor hybrid cells acquire a c-Myc-mediated quasi-polarization state for immunoevasion and distant dissemination.

While macrophage phagocytosis is an immune defense mechanism against invading cellular organisms, cancer cells expressing the CD47 ligand send forward signals to repel this engulfment. Here we report that the reverse signaling using CD47 as a receptor additionally enhances a pro-survival function of prostate cancer cells under phagocytic attack. Although low CD47-expressing cancer cells still allow phagocytosis, the reverse signaling delays the process, leading to incomplete digestion of the entrapped cells and subsequent tumor hybrid cell (THC) formation. Viable THCs acquire c-Myc from parental cancer cells to upregulate both M1- and M2-like macrophage polarization genes. Consequently, THCs imitating dual macrophage features can confound immunosurveillance, gaining survival advantage in the host. Furthermore, these cells intrinsically express low levels of androgen receptor and its targets, resembling an adenocarcinoma-immune subtype of metastatic castration-resistant prostate cancer. Therefore, phagocytosis-generated THCs may represent a potential target for treating the disease.

Double aneuploidy mosaicism involving chromosomes 18 and 21 in a neonate.

BACKGROUND: Double aneuploidy is common, especially in products of conception, frequently involving a combination of a sex chromosome and an acrocentric chromosome. Double autosomal trisomies are rare with only five cases reported. Double aneuploidy mosaicism involving two different cell lines is rarer with only three cases reported. CASE PRESENTATION: We report a fourth case of double aneuploidy mosaicism on a baby. Results of a 24-h preliminary chromosome analysis at birth showed a mosaic karyotype, 47,XX,+18[15]/47,XX,+21[8]/48,XX,+21,+mar[7]. Reflex testing to SNP microarray with the same sample collected at birth showed gain of a 77.9 Mb region on chromosome 18 and gain of a 32.5 Mb region on chromosome 21. Microarray did not show any other copy number variants indicating that the marker chromosome may not contain any euchromatic material. A repeat chromosome analysis at 1-year of age showed a mosaic karyotype, 47,XX,+18[76]/47,XX,+21[4] with loss of the marker cell line. CONCLUSION: Based on our results, we propose that the mosaic double autosomal trisomy in our case was due to two independent non-disjunction events in a normal zygote very early during embryogenesis.

Is 5q deletion in de novo Acute Myelogenous Leukemia (AML) with excess blasts a surrogate marker for the cryptic t(7;21)(p22;q22)? A case report and review of literature.

Although the 5q- syndrome is common in both de novo and treatment related myelodysplastic syndrome (MDS) and the World Health Organization defined 5q- syndrome as a specific type of MDS, it is less common in acute myelogenous leukemia (AML). Recently, it was suggested that AML with diploidy/tetraploidy and/or 5q alterations may be associated with the cryptic translocation, t(7;21)(p22;q22) resulting in RUNX1-USP42 gene fusion and this association may have been underestimated. Here, we report another case of de novo AML with cryptic t(7;21)(p22;q22) associated with a 5q deletion.

Bi-allelic amplification of ATM gene in blastoid variant of mantle cell lymphoma: a novel mechanism of inactivation due to chromoanagenesis?

BACKGROUND: Mantle cell lymphoma (MCL) is derived from naïve CD5+ B-cells with the cytogenetic hallmark translocation 11;14. The presence of additional abnormalities is associated with blastoid variants in MCL (BMCL) and confers a poor prognosis. Many of these tumors also show deletion or loss of heterozygosity (LOH) of the ATM gene and biallelic ATM inactivation show significantly higher chromosomal imbalances. CASE PRESENTATION: Here we report a 52 year-old male who presented to the clinic with worsening dyspnea, fever, chills, diffuse lymphadenopathy, splenomegaly and leukocytosis with blastoid cells circulating in blood. The bone marrow aspirate showed about 40% abnormal blast-looking cells and biopsy revealed a remarkable lymphoid infiltrate. The patient was diagnosed with blastoid variant mantle cell lymphoma (BMCL). Chromosome analysis on bone marrow showed a complex karyotype. FISH analysis from B-cell lymphoma panel showed bi-allelic amplification of ATM gene. Other abnormalities were present including CCND1/IGH fusion, confirming the MCL diagnosis, in addition to RB1 and p53 deletion. High resolution SNP-microarray studies showed complex copy number changes, especially on chromosomes 7 and 11, consistent with chromoanagenesis. Microarray studies also showed LOH at the ATM locus indicating the amplification seen on FISH is not biallelic. CONCLUSION: To the best of our knowledge, ATM gene amplification is not previously reported in BMCL and our case suggests a novel mechanism of ATM inactivation caused by chromoanagenesis resulting in mutant allele specific imbalance with copy number gain.

Copy neutral absence of heterozygosity on chromosome 15 distal long arm: A surrogate marker for Prader-Willi/Angelman syndromes?

BACKGROUND: Copy-neutral absence of heterozygosity (CN-AOH) observed on a single chromosome or part of a chromosome may be indicative of uniparental disomy (UPD) and may require additional testing when such chromosomes or chromosome regions are known to harbor imprinted genes. CASE PRESENTATION: Here we report 2 cases of neonates that presented to clinic with hypotonia, poor oral skills including inability to feed by mouth, weak cry, no response to noxious stimulation and vertical plantar creases (case 1) and hypotonia and respiratory distress (case 2). A preliminary chromosome analysis showed normal karyotypes in both cases while the high-resolution single nucleotide polymorphism (SNP) microarray showed copy neutral absence of heterozygosity involving chromosome 15 distal long arm. In case 1, the CN-AOH involved a 28.7 Mb block from genomic coordinates 73703619_102429049. In case 2, the CN-AOH involved a 15.3 Mb block from genomic coordinates 54729197_70057534. In both cases, methylation-specific PCR did not detect an unmethylated allele for the SNRPN gene suggesting either a deletion of paternal allele or maternal UPD for chromosome 15. Since microarray analysis did not show any copy number alterations on chromosome 15, a microdeletion was ruled out. CONCLUSIONS: Based on our cases, we suggest that CN-AOH on chromosome 15, even if it does not involve the critical region of 15q12q13, should warrant additional studies for diagnosis of Prader-Willi/Angelman syndromes.

Partial hexasomy for the Prader-Willi-Angelman syndrome critical region due to a maternally inherited large supernumerary marker chromosome.

Extra copies of the Prader-Willi-Angelman syndrome critical region (PWASCR) have been shown to have detrimental phenotypic effects depending on the parent of origin. Hexasomy for the PWASCR is rare; only 6 cases have been described to date. We report on a 15-year-old girl referred for developmental delay and seizures with a mosaic tricentric small marker chromosome (SMC) 15 identified by routine G-banding chromosome studies. C-banding and FISH confirmed the presence of three chromosome 15 centromeres as well as four copies of the PWASCR on the SMC in approximately 60% of interphase cells. Microsatellite genotyping documented maternal inheritance of the SMC, and methylation-sensitive multiplex ligation-dependent PCR amplification (MS-MLPA) showed that the extra copies of the PWASCR contained on the marker chromosome bear a methylation pattern similar to a normal maternal chromosome, implying maternal inheritance. These findings are consistent with the patient's phenotype as paternal inheritance of such a marker chromosome is thought to be benign. However, this patient's phenotype is the mildest described to date and may be a result of mosaicism for the SMC.

Molecular cytogenetic characterization of an interstitial de novo 13q deletion in a 3-month-old with severe pediatric gastroesophageal reflux.

Gastroesophageal reflux (GER) occurs when gastric contents travel back into the esophagus through the esophageal sphincter. GER is very common in infants with most growing out of it, but some continue to have chronic symptoms throughout childhood and adulthood. A gene for severe pediatric gastroesophageal reflux disease (GERD) was identified by linkage analysis and was mapped to chromosome 13. We report here a de novo interstitial deletion of chromosome 13 in a 3-month-old biracial male who presented to the emergency room with severe GER and failure to thrive. Chromosome analysis showed an interstitial deletion of chromosome 13, with the karyotype reported as 46, XY, del(13)(q12.3q14.1). BAC-FISH analysis demonstrated that the deletion encompasses 12.3 Mb and does involve the GERD1 locus. The GERD1 locus has been mapped to a 9-cM interval between the markers CAGR1 and D13S263, both of which are deleted in our patient. We propose that the GER phenotype in our patient is due to a haploinsufficiency of GERD1.

Fine mapping of breakpoints in two unrelated patients with rare overlapping interstitial deletions of 9q with mild dysmorphic features.

Approximately, 20 cases of interstitial deletions of 9q have been reported in the literature spanning the breakpoints from 9q21 to 9q34. Unlike the 9q subtelomeric deletions, the interstitial deletions do not demonstrate a specific recognizable phenotype, although the majority of patients had microcephaly. Lack of precise molecular delineation of the extent of deletions in the published cases makes it difficult to develop an accurate genotype-phenotype correlation. We report on fine mapping of breakpoints using the Affymetrix Human Mapping 500K Array Set in two unrelated female patients with overlapping de novo deletion in 9q. SNP oligonucleotide microarray analysis (SOMA) indicated these to be relatively large deletions with Patient 1 having a 6.47 Mb deletion (>60 genes) spanning 9q32-q33.2 and Patient 2 having a 9.68 Mb deletion (>20 genes) localized to 9q31.1-q33.1. FISH analysis with BAC clones localized to the breakpoints showed discrepant results in Patient 1. Based on the review of previously reported interstitial 9q deletion patients and our patients, the minimal region of overlap (MRO) appears to encompass the 9q32 region and a phenotype characterized by microcephaly, neurological dysfunction and facial dysmorphism can be deduced. Our study shows the investigative nature of the latest array technology and the limitations of this technology in the accurate delineation of breakpoints.

Molecular cytogenetic characterization of a unique and complex de novo 8p rearrangement.

Human chromosome 8p is prone to recurrent rearrangements with inv dup del(8p) being most common. Each of these recurrent rearrangements is associated with different clinical manifestations. Some of these recurrent rearrangements at 8p are mediated by an 8p submicroscopic paracentric inversion between the olfactory gene clusters present in one of the parents. However, recent reports have shown that some of the rearrangements are unique and complex and are mediated by other repetitive elements within 8p. Here, we report on a unique and complex 8p rearrangement with seizures as the major presenting feature in the patient. Extensive fluorescence in situ hybridization and microarray analyses with tiling path 8p array showed that the rearrangement is unique in that the 8p duplication is a direct tandem duplication and, unlike the more common inv dup del(8p), is not derived from parental submicroscopic inversion. Also unlike the inv dup del(8p), the phenotype in our case is milder with no central nervous system malformations or cardiac defects.

Identification of Chromothripsis in Biopsy Using SNP-Based Microarray.

One of the well-known hallmarks of cancer is genomic instability. Although gradualism is a well-established process of cancer evolution, recent studies have shown that chromothripsis or chromoanasynthesis can result in complex genomic rearrangements by a single catastrophic event rather than several incremental steps. These two novel phenomena suggest an evolutionary modality for cancer cells to circumvent individual mutational events with one simultaneous shattering of chromosomes or chromosome regions resulting in the random reassembling of shattered genetic material to form complex derivative chromosomes. Although sequencing methods are ideal for the detection of chromothripsis, single-nucleotide polymorphism (SNP)-based microarray methods are also useful in detecting chromothripsis in biopsy samples. Issues related to sample collection, storage, and transport, especially with tumor biopsies, may limit the options for sequencing studies, and in such cases, SNP-based microarray may be a viable alternative for detecting chromothripsis.

Myelodysplasia and Mast Cell Leukemia with t(9;22).

INTRODUCTION: Mast cell leukemia (MCL) is a rare variant of systemic mastocytosis. Most cases of mast cell leukemia do not have cytogenics performed. Furthermore, there is no consistent chromosomal abnormality identified in MCL. This is the first reported case of MCL with a (9;22) translocation. CASE REPORT: An 80-year-old female presented with pancytopenia and was diagnosed with MDS. Over time, she required hospitalizations for platelet transfusions with increased frequency. She developed fatigue and weakness along with gastrointestinal symptoms. On exam, she had diffuse abdominal tenderness and a maculopapular rash. Her lab results revealed a new basophilia. A bone marrow biopsy showed 100% cellularity with many aggregates of mast cells. Chromosomal analysis showed t(9;22) with confirmed BCR/ABL1 fusion by fluorescence in situ hybridization (FISH). DISCUSSION: MCL has a poor prognosis due to the aggressive nature of the disease and ineffective therapies. Translocation (9;22) is known to be associated with MDS transformations to acute leukemia; however, this translocation has never been reported in MCL. Further research on the relationship between t(9;22) and MCL could lead to development of improved therapeutic options.

Optimal strategy for obtaining routine chromosome analysis by using negative fractions of CD138 enriched plasma cells.

Fluorescence in situ hybridization (FISH) is superior to routine chromosome analysis (RCA) in detecting important prognostic genetic abnormalities in plasma cell dyscrasia (PCD); however, its sensitivity is hampered due to paucity of plasma cells (PC) in whole bone marrow (BM). Studies showed that the abnormality detection rate in enriched plasma cells (EPC) is greater than unselected plasma cells (UPC), but purification techniques are limiting to only FISH when sample volumes are inadequate. Not performing RCA may compromise patient care since RCA is equally important for detecting non-PC related abnormalities when the diagnosis is undefined. To resolve this critical issue, we designed a study where an immuno-magnetic CD138 enriched positive selection was used for FISH while the negative fraction (NF) was used to retrieve other myeloid elements for RCA. Parallel FISH studies were performed using UPC and CD138 EPC, while karyotyping was achieved using whole BM and discarded myeloid elements from the NF. Results showed that the abnormality rate of EPC was doubled compared to UPC for FISH, and CA displayed 100% success rate using the NF. PCD related chromosome abnormalities were confined to whole BM while non-PCD related abnormalities were found in both whole BM and NF. Our results demonstrate the feasibility of using the NF for RCA.