Summary
Malignant cells infiltrating the bone marrow (BM) interfere with normal cellular behaviour of supporting cells, thereby creating a malignant niche. We found that CXCR4‐receptor expression was ...increased in paediatric precursor B‐cell acute lymphoblastic leukaemia (BCP‐ALL) cells compared with normal mononuclear haematopoietic cells (P < 0·0001). Furthermore, high CXCR4‐expression correlated with an unfavourable outcome in BCP‐ALL (5‐year cumulative incidence of relapse ± standard error: 38·4% ± 6·9% in CXCR4‐high versus 12% ± 4·6% in CXCR4‐low expressing cases, P < 0·0001). Interestingly, BM levels of the CXCR4‐ligand (CXCL12) were 2·7‐fold lower (P = 0·005) in diagnostic BCP‐ALL samples compared with non‐leukaemic controls. Induction chemotherapy restored CXCL12 levels to normal. Blocking the CXCR4‐receptor with Plerixafor showed that the lower CXCL12 serum levels at diagnosis could not be explained by consumption by the leukaemic cells, nor did we observe an altered CXCL12‐production capacity of BM‐mesenchymal stromal cells (BM‐MSC) at this time‐point. We rather observed that a very high density of leukaemic cells negatively affected CXCL12‐production by the BM‐MSC while stimulating the secretion levels of granulocyte colony‐stimulating factor (G‐CSF). These results suggest that highly proliferative leukaemic cells are able to down‐regulate secretion of cytokines involved in homing (CXCL12), while simultaneously up‐regulating those involved in haematopoietic mobilization (G‐CSF). Therefore, interference with the CXCR4/CXCL12 axis may be an effective way to mobilize BCP‐ALL cells.
A novel DFNA5 mutation was found in a Dutch family, of which 37 members were examined. A nucleotide substitution was identified in the splice acceptor site of intron 7, leading to skipping of exon 8 ...in part of the transcripts. The mutation was found in 18 individuals. Sensorineural hearing impairment was non-syndromic and symmetric. In early life, presumably congenitally, hearing impairment amounted to 30 dB in the high frequencies. Progression was most pronounced at 1 kHz (1.8 dB/year). Speech recognition was relatively good with a phoneme score of about 50% at the age of 70. Onset age was 37 years, and recognition deteriorated by 1.3% per year. The recognition score deteriorated by 1.0% per decibel threshold increase from a mean pure-tone average (PTA at 1, 2 and 4 kHz) of 63 dB onwards. Vestibular function was generally normal. The second mutation identified in the DFNA5 gene results in hearing impairment, similar to that in the original DFNA5 family in terms of pure-tone thresholds, but with more favourable speech recognition.
Myosin VIIA is an unconventional myosin that has been implicated in Usher syndrome type 1B, atypical Usher syndrome, non-syndromic autosomal recessive hearing impairment (DFNB2) and autosomal ...dominant hearing impairment (DFNA11). Here, we present a family with non-syndromic autosomal dominant hearing impairment that clinically resembles the previously published DFNA11 family. The affected family members show a flat audiogram at young ages and only modest progression, most clearly at the high frequencies. In addition, they suffer from minor vestibular symptoms. Linkage analysis yielded a maximum two-point lodscore of 3.43 for marker D11S937 located within 1 cM of the myosin VIIA gene. The myosin VIIA gene was sequenced and 11 nucleotide variations were found. Ten nucleotide changes represent benign intronic variants, silent exon mutations or non-pathologic amino acid substitutions. One variant, a c.1373A-->T transversion that is heterozygously present in all affected family members and absent in 300 healthy individuals, is predicted to result in an Asn458Ile amino acid substitution. Asn458 is located in a region of the myosin VIIA motor domain that is highly conserved in different classes of myosins and in myosins of different species. To evaluate whether the Asn458Ile mutation was indeed responsible for the hearing impairment, a molecular model of myosin VIIA was built based on the known structure of the myosin II heavy chain from Dictyostelium discoideum. In this model, conformational changes in the protein caused by the amino acid substitution Asn458Ile are predicted to disrupt ATP/ADP binding and impair the myosin power-stroke, which would have a severe effect on the function of the myosin VIIA protein.
Hearing threshold was analyzed for each frequency in relation to age in 88 members of a large Dutch family with cochleovestibular impairment caused by a P51S mutation in the COCH gene within the ...DFNA9 locus (chromosome 14q12–13). The participants in this study were 34 mutation carriers and 54 relatives without the mutation (control subjects). A sigmoidal dose-response curve with a variable slope was used to fit the mutation carriers' threshold-on-age data. Progression started at about 40 years of age and only lasted for some 20 to 25 years; the associated average progression was 2.9 dB/y for all frequencies. However, some hearing impairment was already present before, predominantly at the high frequencies. The mean thresholds in the young mutation carriers (<33 years of age) were significantly higher (by 4 to 13 dB) than those in age-matched controls at 2 to 8 kHz. Presumably, mutation carriers have a congenital, stable offset threshold (10 to 29 dB) at these frequencies, and develop progression later in life.
To report hearing impairment and vestibular and ocular features in a Dutch DFNA11 family and to compare these results to reported data on three other DFNA11 families.
Family study.
Regression ...analysis was performed in relation to age to outline the development of hearing thresholds and speech recognition scores. Vestibular and ocular functions were examined.
First symptoms of hearing impairment started between the ages of 4 and 43 years. Most of the audiograms were symmetric and flat or downsloping. The annual threshold deterioration increased from 0.2 to 2.6 dB per year at 0.25 to 8 kHz in the longitudinal analyses and in the cross-sectional analysis from 0.3 to 0.9 dB per year. The speech recognition score was quite good, deteriorating by 0.9% per year from a 90% score at the age of 36 years onward. Remarkably, extensive ocular examination including corrected visual acuity and refraction measurements, slit-lamp examination, ophthalmoscopy, Goldmann perimetry, electroretinography and electro-oculography revealed signs of subclinical retinal dysfunction. None of the patients showed the classic triad of retinitis pigmentosa. Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers were fairly similar to previously described DFNA11 families.
Even though the diverse mutations are located in different regions of the myosin VIIa gene, the cochleovestibular phenotype is fairly similar in all DFNA11 families. Surprisingly, only in this family was subclinical retinal dysfunction detected.
Summary
Malignant cells infiltrating the bone marrow (
BM
) interfere with normal cellular behaviour of supporting cells, thereby creating a malignant niche. We found that
CXCR
4‐receptor expression ...was increased in paediatric precursor B‐cell acute lymphoblastic leukaemia (
BCP
‐
ALL
) cells compared with normal mononuclear haematopoietic cells (
P
<
0·0001). Furthermore, high
CXCR
4‐expression correlated with an unfavourable outcome in
BCP
‐
ALL
(5‐year cumulative incidence of relapse ± standard error: 38·4% ± 6·9% in
CXCR
4‐high
versus
12% ± 4·6% in
CXCR
4‐low expressing cases,
P
<
0·0001). Interestingly,
BM
levels of the
CXCR
4‐ligand (
CXCL
12) were 2·7‐fold lower (
P
=
0·005) in diagnostic
BCP
‐
ALL
samples compared with non‐leukaemic controls. Induction chemotherapy restored
CXCL
12 levels to normal. Blocking the
CXCR
4‐receptor with Plerixafor showed that the lower
CXCL
12 serum levels at diagnosis could not be explained by consumption by the leukaemic cells, nor did we observe an altered
CXCL
12‐production capacity of
BM
‐mesenchymal stromal cells (
BM
‐
MSC
) at this time‐point. We rather observed that a very high density of leukaemic cells negatively affected
CXCL
12‐production by the
BM
‐
MSC
while stimulating the secretion levels of granulocyte colony‐stimulating factor (G‐
CSF
). These results suggest that highly proliferative leukaemic cells are able to down‐regulate secretion of cytokines involved in homing (
CXCL
12), while simultaneously up‐regulating those involved in haematopoietic mobilization (G‐
CSF
). Therefore, interference with the
CXCR
4/
CXCL
12 axis may be an effective way to mobilize
BCP
‐
ALL
cells.
Malignant cells that infiltrate the bone marrow (BM) interfere with the normal cellular behavior of supporting cells, thereby creating an alternative malignant niche. This intercellular communication ...is mostly mediated by cytokines and their receptors. In this study, we find that expression of the CXCR4 receptor is significantly increased in pediatric precursor B-cell acute lymphoblastic leukemia (BCP-ALL) cells compared with normal mononuclear hematopoietic cells derived of the bone marrow (p=0.016). Furthermore, we show that high CXCR4 expression is correlated with an unfavorable clinical outcome in BCP-ALL (5-yr CIR ±SE: 38.4% ±6.9% in CXCR4-high versus 12.0% ±4.6% in CXCR4-low expressing patients, p<0.001). Interestingly, BM serum levels of the CXCR4 ligand (CXCL12) are 2.7-fold lower (p=0.005) in samples taken at initial diagnosis of BCP-ALL compared with the levels in samples taken of non-leukemic controls. We show that induction chemotherapy restores CXCL12 levels in the BM to normal levels. Blocking the CXCR4 receptor with Plerixafor (FDA-approved drug) showed that the lower CXCL12 serum levels at initial diagnosis could not be explained by consumption by the leukemic cells, nor did we observe an altered CXCL12-production capacity of BM-MSC at this time-point. We rather observed that a very high density of leukemic cells negatively affected CXCL12 production by the BM-MSC while stimulating the secretion levels of G-CSF. These results suggest that highly proliferative leukemic cells are able to down-regulate the production of cytokines involved in homing (CXCL12), while simultaneously up-regulating the production of cytokines involved in hematopoietic mobilization (G-CSF). This disbalance may stimulate the spreading of BCP-ALL outside the BM.
The data presented here suggest that interference with the CXCR4/CXCL12 axis (for instance by using Plerixafor) may be an effective way to mobilize BCP-ALL cells; the more ALL cells become mobilized, the less ALL cells may escape from combination chemotherapy. In proof-of concept studies, this hypothesis needs to be validated to pave the way for implementation in future treatment protocols for children with ALL.
No relevant conflicts of interest to declare.
Usher syndrome type II (USH2) is a genetically heterogeneous autosomal recessive disorder with at least three genetic subtypes (USH2A, USH2B, and USH2C) and is classified phenotypically as congenital ...hearing loss and progressive retinitis pigmentosa. The VLGR1 ( MASS1 ) gene in the 5q14.3-q21.1 USH2C locus was considered a likely candidate on the basis of its protein motif structure and expressed-sequence-tag representation from both cochlear and retinal subtracted libraries. Denaturing high-performance liquid chromatography and direct sequencing of polymerase-chain-reaction products amplified from 10 genetically independent patients with USH2C and 156 other patients with USH2 identified four isoform-specific VLGR1 mutations (Q2301X, I2906FS, M2931FS, and T6244X) from three families with USH2C, as well as two sporadic cases. All patients with VLGR1 mutations are female, a significant deviation from random expectations. The ligand(s) for the VLGR1 protein is unknown, but on the basis of its potential extracellular and intracellular protein-protein interaction domains and its wide mRNA expression profile, it is probable that VLGR1 serves diverse cellular and signaling processes. VLGR1 mutations have been previously identified in both humans and mice and are associated with a reflex-seizure phenotype in both species. The identification of additional VLGR1 mutations to test whether a phenotype/genotype correlation exists, akin to that shown for other Usher syndrome disease genes, is warranted.
