The sesquiterpene lactone parthenolide induces selective apoptosis of B-chronic lymphocytic leukemia cells in vitro

We have studied the in vitro actions of the sesquiterpene lactone parthenolide (PTL) on cells isolated from patients with chronic lymphocytic leukemia (CLL). Dye reduction viability assays showed that the median LD(50) for PTL was 6.2 muM (n=78). Fifteen of these isolates were relatively resistant to the conventional agent chlorambucil but retained sensitivity to PTL. Brief exposures to PTL (1-3 h) were sufficient to induce caspase activation and commitment to cell death. Chronic lymphocytic leukemia cells were more sensitive towards PTL than were normal T lymphocytes or CD34(+) haematopoietic progenitor cells. The mechanism of cell killing was via PTL-induced generation of reactive oxygen species, resulting in turn in a proapoptotic Bax conformational change, release of mitochondrial cytochrome c and caspase activation. Parthenolide also decreased nuclear levels of the antiapoptotic transcription factor nuclear factor-kappa B and diminished phosphorylation of its negative regulator IkappaB. Killing of CLL cells by PTL was apparently independent of p53 induction. This is the first report showing the relative selectivity of PTL towards CLL cells. The data here warrant further investigation of this class of natural product as potential therapeutic agents for CLL.

Idiopathic gonadotrophin deficiency: genetic questions addressed through phenotypic characterization

OBJECTIVE

The association of idiopathic hypogonadotrophic hypogonadism (IHH) with congenital olfactory deficit defines Kallmann's syndrome (KS). Although a small proportion of IHH patients have been found to harbour defined genetic lesions, the genetic basis of most IHH cases remains to be elucidated. Genes currently recognized to be involved comprise KAL (associated with X-linked-KS), the GnRH receptor (associated with resistance to GnRH therapy), DAX 1 (associated with adrenohypoplasia congenita) and three loci also associated with obesity, leptin (OB), leptin receptor (DB) and prohormone convertase (PC1). Because of the rarity of the condition and the observation that patients are almost universally infertile without assistance, familial transmission of IHH is encountered infrequently and pedigrees tend to be small. This has constrained the ability of conventional linkage studies to identify other candidate loci for genetic IHH. We hypothesized that a systematic clinical evaluation of a large patient sample might provide new insights into the genetics of this rare disorder. Specifically, we wished to examine the following propositions. First, whether normosmic (nIHH) and anosmic (KS) forms of IHH were likely to be genetically discrete entities, on the basis of quantitative olfactory testing, analysis of autosomal pedigrees and the prevalence of developmental defects such as cryptorchidism and cleft palate. Second, whether mirror movements and/or unilateral renal agenesis were specific phenotypic markers for X-linked-KS.

DESIGN AND PATIENTS

We conducted a clinical study of 170 male and 45 female IHH patients attending the endocrinology departments of three London University teaching hospitals. Approximately 80% of data were obtained from case records and 20% collected prospectively. Parameters assessed included olfaction, testicular volume, family history of hypogonadism, anosmia or pubertal delay, and history or presence of testicular maldescent, neurological, renal or craniofacial anomalies. Where possible, the clinical information was correlated with published data on genetic analysis of the KAL locus.

RESULTS

Olfactory acuity was bimodally distributed with no evidence for a spectrum of olfactory deficit. Testicular volume, a marker of integrated gonadotrophin secretion, did not differ significantly between anosmic and normosmic patients, at 2.0 ml and 2.2 ml, respectively. Nevertheless, the prevalence of cryptorchidism was nearly three times greater in anosmic (70.3%, of which 75.0% bilateral) than in normosmic (23.2%, of which 43.8% bilateral) patients. Individuals with nIHH, eugonadal isolated anosmia and/or KS were observed to coexist within 6/13 autosomal IHH pedigrees. On three occasions, fertility treatment given to an IHH patient had resulted in the condition being transmitted to the resulting offspring. Mirror movements and unilateral renal agenesis were observed in 24/98 and 9/87 IHH patients, respectively, all of whom were identifiable as X-KS males on the basis of pedigree analysis and/or defective KAL coding sequence. Abnormalities of eye movement and unilateral sensorineural deafness were observed in 10/21 and 6/111 KS patients, respectively, but not in nIHH patients.

DISCUSSION

Patients with IHH are almost invariably either anosmic (KS) or normosmic (nIHH), rather than exhibiting intermediate degrees of olfactory deficit. Moreover, the prevalence of cryptorchidism is nearly three times greater in KS than in nIHH despite comparable testicular volumes, suggesting a primary defect of testicular descent in KS independent of gonadotrophin deficiency. Disorders of eye movement and hearing appear only to occur in association with KS. Taken together, these findings indicate a clear phenotypic separation between KS and nIHH. However, pedigree studies suggest that autosomal KS is an heterogeneous condition, with incomplete phenotypic penetrance within pedigrees, and that some cases of autosomal KS, nIHH and even isolated anosmia are likely to have a common genetic basis. The prevalences of anosmia, mirror movements and unilateral renal agenesis among X-KS men are estimated to be 100, 85 and 31%, respectively. In sporadic IHH, mirror movements and unilateral renal agenesis are 100% specific phenotypic markers of de novo X-KS. By comparison, only 7/10 X-KS families harboured KAL coding defects. Clinical ascertainment, using mirror movements, renal agenesis and ichthyosis as X-KS-specific phenotypic markers, suggested that de novo X-KS was unlikely to comprise more than 11% of sporadic cases. The majority of sporadic KS cases are therefore presumed to have an autosomal basis and, hence, the preponderance of affected KS males over females remains unexplained, though reduced penetrance in women would be a possibility.

Contrasting expression of KAL in cell-free systems: 5' UTR and coding region structural effects on translation

We investigated the expression of two different X-linked Kallmann (KAL) gene cDNAs in two different cell-free systems using rabbit reticulocyte lysate: (system A) transcription/translation coupled and (system B) noncoupled. System A yielded a single band of 76 kDa corresponding to anosmin-1, the expected full-length gene product, and upon addition of canine microsomal membranes produced a 85-kDa glycosylated form. System B did not produce any detectable protein band despite the expression of a beta-galactosidase-positive control gene. The first 179 bases of the coding sequence are 74% GC-rich and showed the potential to form imperfect hairpin structures, which in part may explain the translation inhibition of KAL in system B. This has further led us to speculate that coupling transcription to translation may either be preventing translating-inhibiting hairpin formation or be compensating for the lack of certain tissue-specific proteins in reticulocyte lysate that are essential in overcoming inhibitory hairpins during translation. Substitution of the 5'-UTR with an encephalomyocarditis virus internal ribosomal entry site (EMCV IRES) sequence resulted paradoxically in a lower yield of anosmin-1, suggesting that elements in the 5'UTR may be necessary for maintaining a "normal" level of expression. The use of KAL and luciferase reporters (containing different 5'UTRs) demonstrated that the native KAL 5' UTR is not involved in translational efficiency. However, this sequence may influence faithful translation initiation. Theoretical RNA conformation data imply that effective EMCV IRES usage with KAL may require favorable pairing between the IRES and unidentified sequences within the 5' coding region of the gene. This work provides a foundation both for the investigation of KAL regulation and for the characterization of its function.

X-linked ichthyosis with hypogonadism: not always Kallmann's syndrome

We describe two males with congenital ichthyosis secondary to steroid sulphatase deficiency who also manifested delayed puberty with biochemical features of hypogonadotrophic hypogonadism. In the first patient a history of cryptorchidism and the clinical findings of anosmia, micropenis and bimanual synkinesis suggested a contiguous gene syndrome, comprising X-linked Kallmann's syndrome and X-linked ichthyosis. An X-Y chromosomal translocation involving the Xp22.3 locus was identified; deletions of the STS locus and of exons 10-14 of the KAL locus were subsequently demonstrated. The second patient was euosmic and, although the STS locus was deleted in association with a pericentric inversion involving Xp22.3, no deletions were detected at the KAL locus. Clinically, he was felt to have constitutionally delayed puberty rather than hypogonadotropic hypogonadism and this diagnosis was substantiated by his subsequent development.

The neuroradiology of Kallmann's syndrome: a genotypic and phenotypic analysis

A detailed neurological investigation of patients with Kallmann's syndrome (KS) has been performed in an attempt to relate phenotypic characterization with genotype. Twenty-seven subjects with KS were studied (including 12 males with X-linked disease and 3 females). Six male and 2 female normosmics with isolated GnRH deficiency, 1 male with KS variant, and 1 obligate female carrier were also imaged. Evidence for X-linked disease was derived both from analysis of pedigree and by mutation analysis at the KAL locus. The female carrier and all 8 normosmics had normal olfactory bulbs and sulci, as did 3 male KS. The study, therefore, confirms the value of magnetic resonance imaging in the diagnosis of KS, but suggests that the technique is not sufficiently sensitive to differentiate KS from the normosmic form of GnRH deficiency in all cases. Phenotypic characterization of KS was more effectively achieved by accurate estimation of olfactory status. Three new mutations at the KAL locus were identified, 2 single exon deletions and 1 point mutation. In 2 pedigrees with clear X-linked inheritance, no coding sequence mutations were detected; it may be that these harbor mutations of pKAL, the recently characterized 5'-promoter region. No clear relationship could be established between specific phenotypic anomalies and particular KAL mutations. Involuntary, mirror movements of the upper limbs were present in 10 of 12 cases of X-linked KS, but in none of the other subjects. Although this phenomenon has been ascribed to an abnormality of the corpus callosum, in the present study magnetic resonance imaging demonstrated no quantitative or qualitative morphological anomalies of this structure.

KAL, a gene mutated in Kallmann's syndrome, is expressed in the first trimester of human development

Kallmann's syndrome (KS) is characterised by the association of anosmia and isolated hypogonadotrophic hypogonadism (IHH). Mutations of the KAL gene which is located at Xp22.3 cause X-linked KS (XKS). In this study we used the reverse transcriptase polymerase chain reaction and in situ hybridisation to examine the developmental expression of KAL in the first trimester of pregnancy, the earliest stage of human gestation examined thus far. At 45 days after fertilisation KAL mRNA was detected in the spinal cord, the mesonephros and metanephros but not in the brain. Later in gestation, at 11 weeks, the gene was expressed in the developing olfactory bulb, retina and kidney. This expression pattern correlates with the clinical findings in XKS since olfactory bulb dysgenesis with subsequent defective neural migration causes anosmia and IHH. Additionally, renal agenesis occurs in 40% of patients. Therefore this study provides strong evidence that KAL expression is required for the normal development of the olfactory bulb and kidney in the first trimester of human pregnancy.