Gonadotropic status in adult women with pituitary stalk interruption syndrome.

OBJECTIVE: Pituitary stalk interruption syndrome (PSIS) is a rare cause of congenital hypopituitarism. Limited data exist on the gonadotropic status and fertility of adult women with PSIS. Our study aims to describe pubertal development and the evolution of gonadotropic function and fertility in adult women with PSIS. DESIGN: Retrospective multicentric French study. METHODS: We described gonadotropic function in 56 adult women with PSIS from puberty onwards. We compared live birth rates per woman with PSIS to age-matched controls from the large French epidemiological cohort (CONSTANCES). Additionally, we assessed height, BMI, blood pressure, other metabolic parameters, and socio-economic status. RESULTS AND CONCLUSIONS: Among 56 women with PSIS, 36 did not experience spontaneous puberty. Of these, 13 underwent ovarian stimulation resulting in 7 women having a total of 11 children. In the subgroup with spontaneous puberty (n = 20), 4 had a total of 8 pregnancies while 6 developed secondary gonadotropic deficiency. Women with PSIS had fewer children than controls (0.33 versus 0.63, p = 0.04). Median height was also lower (160.5 cm versus 165.0 cm, p < 0.0001). Although mean blood pressure was lower in women with PSIS compared to controls, (111.3/65.9 ± 11.2/8.1 mmHg vs 118.7/72.1 ± 10.1/7.7 mmHg, p < 0.001), there were no significant differences in other metabolic parameters, notably BMI and lipid profile. Employment/academic status was not different in the two groups but fewer women with PSIS were in relationships (42% versus 57.6% in controls, p = 0.02). The fertility prognosis in patients with PSIS needs optimization. Patients should be informed about the likelihood of declining gonadotropic function over time.

Progestin-associated shift of meningioma mutational landscape.

Background: Meningiomas are the most common primary tumor of the central nervous system. The relationship between meningioma and progestins is frequently mentioned but has not been elucidated. Patients and methods: We identified 40 female patients operated for a meningioma after long-term progestin therapy and performed targeted next generation sequencing to decipher the mutational landscape of hormone-related meningiomas. A published cohort of 530 meningiomas in women was used as a reference population. Results: Compared with the control population of meningiomas in women, progestin-associated meningiomas were more frequently multiple meningiomas [19/40 (48%) versus 25/530 (5%), P < 10-12] and located at the skull base [46/72 (64%) versus 241/481 (50%), P = 0.03]. We found a higher frequency of PIK3CA mutations [14/40 (35%) versus 18/530 (3%), P < 10-8] and TRAF7 mutations [16/40 (40%) versus 140/530 (26%), P < 0.001] and a lower frequency of NF2-related tumors compared with the control population of meningiomas [3/40 (7.5%) versus 169/530 (32%), P < 0.001]. Conclusion: This shift in mutational landscape indicates the vulnerability of certain meningeal cells and mutations to hormone-induced tumorigenesis. While the relationship between PIK3CA mutation frequency and hormone-related cancers such as breast and endometrial cancer is well-known, this hormonally induced mutational shift is a unique feature in molecular oncology.

[Manifestations and prognosis of thyrotropin-secreting pituitary adenomas: a case series of three patients]. / Présentation et pronostic des adénomes thyréotropes: à propos de trois observations.

INTRODUCTION: Among pituitary adenomas, thyrotropinomas were previously considered as extremely rare and resistant to therapy. However, the common use of the sensitive TSH measurement and the improvement of pituitary imaging have modified their clinical and hormonal presentation. CASE REPORTS: We here report three cases of TSH secreting pituitary adenoma that highlight the great diversity of the clinical, hormonal and morphological presentation, and their better prognosis. In the presence of an inappropriate TSH secretion, the main differential diagnosis is the syndrome of thyroid hormone resistance. The role of somatostatin analogue prior to the surgical treatment of TSH secreting pituitary adenoma is also underlined in this report. CONCLUSION: The increasing frequency and early diagnosis of TSH secreting pituitary adenoma may be explained by ultrasensitive methods now used for TSH measurement and progress in pituitary imaging, mainly with MRI. This changing spectrum in the presentation and the excellent response to somatostatin analogues improved in the prognosis of the disease.

[Anaesthesia for endocrine tumor removal]. / Anesthésie pour traitement des tumeurs endocrines.

Endocrine tumors could be defined by their ability to produce structural proteins or hormones common to nervous and endocrine cells. They might induce physiological transforms or outcome adverse events which should be well known in order to prevent or treat them early. The goal of this review was to describe these changes, to describe preoperative assessment, and to discuss intraoperative monitoring and drugs choice based on the literature from the last 30 years. As an example, it should be noticed that: (1) preoperative blood pressure control is essential to prepare phaeochromocytoma for surgery. It should be followed during anaesthesia by intensive fluid load, reversible anaesthetic drugs and rational cardiovascular medications use (as for example remifentanil, sevoflurane, calcium channel blockers and esmolol), and after surgery by narrow clinical and biological monitoring; (2) after medullar thyroid cancer, main adverse events include cervical compressive haematoma and recurrent laryngeal nerve injury as for any thyroid surgery; (3) during pituitary surgery, air embolism might be expected, whereas water dysregulation (diabetes insipidus), corticotroph insufficiency, cerebrospinal fluid (CSF) leak might occur postoperatively. In acromegaly, difficult endotracheal intubation is possible whereas severe Cushing's syndrome may be complicated with hypertensive cardiac failure, infections, thrombosis, delayed cicatrisation; (4) somatostatine analogs are a keystone in carcinoid tumors preoperative and anaesthetic management.

[Management of hypercortisolism]. / Prise en charge d'un hypercorticisme.

PURPOSE: Cushing's syndrome is a rare but frequently considered disease. Its diagnosis can lead to some difficulties, including confirming the effective endogenous hypercortisolism and determining its cause. The severity of this disease, the diversity of its complications and the multiple therapeutic options make its management challenging. The aim of this review is to present the most recent data about management of Cushing's syndrome, especially diagnostic approaches and therapeutic options. Our references were obtained by screening MEDLINE database from 1996 to 2006. We also included some anterior reviews and consensus statements. MAIN POINTS: We retained the following points: midnight salivary cortisol is a useful tool in the diagnosis of Cushing's syndrome; the desmopressin test can help to distinguish between Cushing's syndrome and "pseudoCushing's" due to alcohol consumption or psychiatric disorders; cavernous sinus and inferior petrosal sinus sampling is indicated in the evaluation of ACTH-dependent Cushing's syndromes when pituitary imaging is normal or equivocal or when dynamic tests are contradictory; multislice computed-tomography of the chest and the abdomen and somatostatin analogue scintigraphy, eventually combined, are the best imaging procedures in occult ectopic ACTH syndromes; patients with Cushing's disease should be referred to a neurosurgeon experienced in corticotroph adenomas surgery; metabolic consequences of Cushing's syndrome, such as cardiovascular risk factors and osteoporosis need an aggressive treatment. PERSPECTIVES: The incidence of Cushing's syndrome is only 1/100000 per year. However, hypercortisolism is diagnosed by systematic evaluation in 2 to 5% of patients with poorly controlled type 2 diabetes and adrenal incidentalomas. Endocrinological management of the disease improves metabolic disorders in these patients. If these results are confirmed, screening for Cushing's syndrome should be systematically performed in these populations.

Proopiomelanocortin, a polypeptide precursor with multiple functions: from physiology to pathological conditions.

Proopiomelanocortin (POMC) is the polypeptide precursor of ACTH. First discovered in anterior pituitary corticotroph cells, it has more recently been revealed to have many other physiological aspects. The fine molecular mechanisms of ACTH biosynthesis show that ACTH is but one piece of a puzzle which contains many other peptides. Present in various tIssues, among which are pituitary, hypothalamus, central nervous system and skin, POMC undergoes extensive post-translational processing. This processing is tIssue-specific and generates, depending on the case, various sets of peptides involved in completely diverse biological functions. POMC expressed in corticotroph cells of the pituitary is necessary for adrenal function. Recent developments have shown that POMC-expressing neurons in the brain play a major role in the control of pain and energy homeostasis. Local production of POMC-derived peptides in skin may influence melanogenesis. A still unknown function in the placenta is likely.POMC has become a paradigmatic polypeptide precursor model illustrating the variable roles of a single gene and its various products in different localities.

[Sulfasalazine neurotoxicity]. / Neurotoxicité à la sulfasalazine.

We report a case of seizures with acute encephalopathy in a female patient under sulfasalazine treatment for polyarthritis. Neurotoxicity secondary to sulfasalazine was suspected. This side effect has seldom been reported in the literature.

A new generation IRMA for ACTH with improved specificity: validation in various physiological and pathological conditions.

OBJECTIVE: Measurement of plasma ACTH is a key step for the exploration of hypothalamic-pituitary-adrenal disorders. To further improve ACTH recognition a new generation of ACTH IRMA was developed using antibodies directed towards succinylated ACTH (sACTH IRMA). DESIGN: The usefulness of this assay was compared with that of another commercially available ACTH IRMA assay using intact ACTH (ELSA-ACTH) in various pathophysiological situations: patients with low ACTH plasma levels, high ACTH plasma levels with normal or tumoural pituitaries, or ectopic ACTH syndrome, and pregnant women with high proopiomelanocortin (POMC) plasma levels. METHODS: All plasma samples were assayed simultaneously with the two different IRMAs. Comparisons were assessed by plotting the results along the theoretical line of identical values, and by the graphical method of Bland and Altman. RESULTS: In the ELSA-ACTH IRMA, CLIP (or ACTH18-39) showed true cross-reactivity, and alpha-melanocyte-stimulating hormone and purified POMC both interfered and induced falsely lower ACTH results; in the sACTH IRMA no peptide showed any cross-reactivity, and only extremely high values of CLIP (50 000 pg/ml) interfered and induced falsely lower ACTH results. In ACTH hypersecretory syndromes, of tumoural (Cushing's disease, ectopic ACTH secretion) or non-tumoural (Addison's disease, congenital adrenal hyperplasia) origins a good agreement between the two assays was observed except for very high ACTH plasma values (above 1000 pg/ml) and in some tumours where the sACTH IRMA yielded lower results; in some cases, the presence of circulating CLIP, demonstrated by HPLC studies, may contribute to this discrepancy. It is also likely that the calibration of the ELSA-ACTH kit itself generates higher ACTH values. In normal pregnant women both IRMAs gave highly correlated values, yet lower results were obtained with the sACTH IRMA. CONCLUSION: These data show that the sACTH IRMA has improved qualities of specificity and usefulness for rapid assessment of ACTH plasma levels.

Lipodystrophy associated with protease inhibitors.

Lipodystrophies, characterized by reduction of subcutaneous fat over part or all of the body surface, are uncommon. Their causes are unknown. Recently, lipodystrophy has been reported in human immunodeficiency virus (HIV)-infected patients taking protease inhibitors, which have been recommended since 1996 as standard therapy for HIV disease in combination with nucleoside analogues. In these cases, lipodystrophy consists of an association of peripheral lipoatrophy with central adiposity. We report four HIV-infected men on protease inhibitors who developed a disfiguring lipodystrophy. In three of them, the protease inhibitor was administered for a mean duration of 21.5 months (range 19-23) with good immunological and virological responses. Patient 4 had been treated for 2 years with successive combinations of protease inhibitors with nucleoside analogues without success. The four patients progressively developed an increase in abdominal girth associated with fat wasting of the face and legs. Two of them had recurrent paronychia of the great toes. Triglyceride levels were moderately increased in all patients, and one had a slightly increased cholesterol level. One patient had elevated glucose and insulin plasma levels during a glucose tolerance test. In two patients, a deep biopsy taken from the thigh showed thinning of the subcutaneous fat without other morphological changes. Computed tomographic scans of the face and abdomen confirmed the loss of almost all subcutaneous fat of the cheek and temporal regions, and abdominal perivisceral fat accumulation. For patients 1-3, the protease inhibitor was replaced by a non-nucleoside reverse transcriptase inhibitor. Nine months later, dysmorphic changes had not regressed, but lipid abnormalities had returned to normal and the paronychia had disappeared.

Pro-opiomelanocortin in human pregnancy: evolution of maternal plasma levels, concentrations in cord blood, amniotic fluid and at the feto-maternal interface.

OBJECTIVE: The human placenta normally expresses the pro-opiomelanocortin (POMC) gene. The pattern and secretory kinetics of POMC and/or POMC-derived peptides by the placenta during gestation is still debated. We recently demonstrated that full length POMC was a normal product of the human placenta. The aim of our study was to establish its normal secretory kinetics and to explore its physiological relevance. DESIGN: In a prospective, longitudinal study, thirty normal pregnant women had monthly measurements of plasma POMC. In a cross-sectional study of 128 healthy pregnant women, plasma POMC and human chorionic gonadotrophin (hCG) were concomitantly measured to assess their correlation. Finally, POMC levels were assessed in venous and arterial cord blood samples, in amniotic fluid and in retroplacental blood. METHODS: Plasma POMC was measured by a specific IRMA in unextracted blood or biological fluid. RESULTS: Plasma POMC became detectable by the 8th week of pregnancy and reached its maximum at around the 20th week, remaining stable thereafter. The relationship between POMC and gestation time (weeks) best fitted with a third degree polynomia curve. A significant negative correlation (P=0.01) was observed between plasma levels of POMC and hCG after adjustment for gestation time to take into account the dependence of both hormones on this parameter. POMC was not secreted into the fetal circulation at term, but was present in very high levels in amniotic fluid. The highest levels of POMC were present in the retroplacental blood where the values were 35 times higher than in maternal blood; by comparison, corticotrophin releasing hormone and ACTH values in this compartment were twice or equal to those in the maternal blood. CONCLUSION: Placental POMC secretion increases during the first half of pregnancy and reaches a plateau from the 20th week to delivery. The inverse correlation between POMC and hCG plasma levels, and very high POMC levels at the feto-maternal interface suggest a physiological role for this precursor during pregnancy.

High precursor level in maternal blood results from the alternate mode of proopiomelanocortin processing in human placenta.

OBJECTIVE: ACTH-producing non-pituitary tumours are often associated with altered precursor processing, particularly in the most aggressive ones. Since placental tissue is characterized by its ability to express the proopiomelanocortin (POMC) gene and rapid cellular proliferation, we examined whether intact POMC could be released physiologically during human gestation. SUBJECTS: One hundred and fifty six normal pregnant women, 12 with multiple pregnancies, and 23 non-pregnant controls. Twenty-eight women were studied in the immediate postpartum period. MEASUREMENTS: We measured plasma POMC levels with a specific immunoradiometric assay (IRMA) using a combination of antibodies directed against ACTH and beta endorphin. Results obtained with this first IRMA were confirmed in 22 subjects with a second assay using the same beta endorphin antibody and a more distal antibody directed against the N-terminal fragment of POMC. Reverse transcription-PCR detected full length, pituitary-like, POMC mRNA in human placenta. RESULTS: Plasma POMC was undetectable (< 60 U/ml) in 23 normal subjects. In normal monofetal pregnancies, POMC became detectable in most women by the third month and then increased steadily until midgestation: 168 +/- 108 (U/ml; mean +/- SD) between 12 and 15 weeks, 190 +/- 103 between 16 and 19 weeks, 324 +/- 180 between 20 and 23 weeks, 276 +/- 171 between 24 and 27 weeks, 292 +/- 177 between 28 and 31 weeks, 290 +/- 235 between 32 and 35 weeks and 308 +/- 210 between 36 weeks and parturition. Plasma POMC was significantly higher in multiple pregnancies with very high levels in three triplet-bearing mothers: 671, 941, and 1731 U/ml at 31, 33 and 32 weeks, respectively. POMC levels felt quickly in post partum, becoming undetectable in five of 13 women on day 1, seven of eight on day 2 and five of six on day 3. Plasma POMC displayed no diurnal variation, was not suppressed by glucocorticoid administration and did not correlate with plasma ACTH or cortisol. In contrast, plasma POMC positively correlated with plasma CRH. CONCLUSIONS: Pregnancy is the only condition in which POMC is produced and released physiologically, similar in some respects to the ectopic ACTH syndrome. POMC is derived solely from the placenta, with no interference from maternal pituitary secretion, and is thus a new and specific placental marker.

Variable expression of the V1 vasopressin receptor modulates the phenotypic response of steroid-secreting adrenocortical tumors.

We studied the putative role of the vasopressin receptors in the phenotypic response of steroid-secreting adrenocortical tumors. A retrospective analysis of a series of 26 adrenocortical tumors responsible for Cushing's syndrome (19 adenomas and 7 carcinomas) showed that vasopressin (10 IU, i.m., lysine vasopressin) induced an ACTH-independent cortisol response (arbitrarily defined as a cortisol rise above baseline of 30 ng/mL or more) in 7 cases (27%). In comparison, 68 of 90 patients with Cushing's disease (76%) had a positive cortisol response. We then prospectively examined the expression of vasopressin receptor genes in adrenocortical tumors of recently operated patients (20 adenomas and 19 adrenocortical carcinomas). We used highly sensitive and specific quantitative RT-PCR techniques for each of the newly characterized human vasopressin receptors: V1, V2, and V3. The V1 messenger ribonucleic acid (mRNA) was detected in normal adrenal cortex and in all tumors. Its level varied widely between 2.0 x 10(2) and 4.4 x 10(5) copies/0.1 microgram total RNA, and adenomas had significantly higher levels than carcinomas, although there was a large overlap. Among the 6 recently operated patients who had been subjected to the vasopressin test in vivo, the tumor V1 mRNA levels were higher in the 4 responders (9.5 x 10(3) to 5.0 x 10(4)) than in the 2 nonresponders (2.0 x 10(2) and 1.8 x 10(3)). One adenoma that had a brisk cortisol response in vivo, also had in vitro cortisol responses that were inhibited by a specific V1 antagonist. In situ hybridization showed the presence of V1 mRNA in the normal human adrenal cortex where the signal predominated in the compact cells of the zona reticularis. A positive signal was also present in the tumors with high RT-PCR V1 mRNA levels; its distribution pattern was heterogeneous and showed preferential association with compact cells. RT-PCR studies for the other vasopressin receptors showed a much lower signal for V2 and no evidence for V3 mRNA. We could not establish whether the V2 mRNA signal observed in normal and tumoral specimens was present within adrenocortical cells or merely within tissue vessels. We conclude that the vasopressin V1 receptor gene is expressed in normal and tumoral adrenocortical cells. High, and not ectopic, expression occurs in a minority of tumors that become directly responsive to vasopressin stimulation tests.

[Ectopic ACTH secretion: a heterogeneous entity]. / Sécrétion ectopique d'ACTH: une entité hétérogène.

OBJECTIVES: ACTH-secreting non-pituitary tumors are a rare cause of Cushing's disease. We report the clinical course, prognostic aspects and molecular analysis data in three patients for whom the diagnosis was confirmed but who had variable clinical features and laboratory results. CASE REPORTS: Patient n degree 1 had severe hypercorticism which rapidly progressed to death 13 months after diagnosis. In patient n degree 2, signs of hypercorticism severe, leading to death 5 years after discovery of the causal carcinoid tumor. Patient n degree 3 had moderate hypercorticism and has survived for more than 25 years. DISCUSSION: These 3 ectopic tumors are representative examples of a wide range of possible ACTH-secreting ectopic tumors. In highly malignant poorly-differentiated tumors such as small-cell anaplastic carcinomas, ACTH production is aberrant and poorly controlled, and thus not particularly effective. At the other extreme, typical benign bronchial carcinomas have a high degree of neuroendocrine differentiation and secrete ACTH in a well-controlled manner difficult to distinguish from corticotropic adenomas, further exaggerating the diagnostic pitfalls.

Structural and functional abnormalities at 11p15 are associated with the malignant phenotype in sporadic adrenocortical tumors: study on a series of 82 tumors.

Abnormalities of the 11p15 region with overexpression of the normally imprinted insulin-like growth factor II (IGF-II) gene have been implicated in the pathogenesis of adrenocortical tumors. We evaluated the frequency and distribution of 11p15 loss of heterozygosity (LOH) and IGF-II gene overexpression in a series of 82 sporadic adrenocortical tumors, screened for pathological functional imprinting of the 11p15 region in tumors not exhibiting LOH and evaluated the expression of H19 gene in these tumors. Abnormalities of the 11p15 region as LOH (loss of the maternal allele and duplication of the paternal allele) and/or IGF-II gene overexpression are frequent features of the malignant state and were found in 27 of 29 (93.1%) of the malignant tumors and in only 3 of 35 (8.6%) of the benign tumors. Tumors without abnormality of the 11p15 region (mainly benign tumors) did not exhibit pathological functional imprinting. In tumors with mosaicism for 11p15 LOH, biallelic expression of the IGF-II gene was constant in the tumor cell contingent not undergoing LOH. Abrogation of H19 expression correlated with the loss of the maternal allele (LOH or pathological imprinting), but did not always correlate with overexpression of the IGF-II gene. These data indicate the involvement of dysregulation of the 11p15 region in late steps of adrenocortical tumorigenesis and provide us with new molecular markers for a better diagnostic and prognostic evaluation of adrenocortical tumors.

Obesity and impaired prohormone processing associated with mutations in the human prohormone convertase 1 gene.

Human obesity has an inherited component, but in contrast to rodent obesity, precise genetic defects have yet to be defined. A mutation of carboxypeptidase E (CPE), an enzyme active in the processing and sorting of prohormones, causes obesity in the fat/fat mouse. We have previously described a women with extreme childhood obesity (Fig. 1), abnormal glucose homeostasis, hypogonadotrophic hypogonadism, hypocortisolism and elevated plasma proinsulin and pro-opiomelanocortin (POMC) concentrations but a very low insulin level, suggestive of a defective prohormone processing by the endopeptidase, prohormone convertase 1 (PC1; ref. 4). We now report this proband to be a compound heterozygote for mutations in PC1. Gly-->Arg483 prevents processing of proPC1 and leads to its retention in the endoplasmic reticulum (ER). A-->C+4 of the intro-5 donor splice site causes skipping of exon 5 leading to loss of 26 residues, a frameshift and creation of a premature stop codon within the catalytic domain. PC1 acts proximally to CPE in the pathway of post-translational processing of prohormones and neuropeptides. In view of the similarity between the proband and the fat/fat mouse phenotype, we infer that molecular defects in prohormone conversion may represent a generic mechanism for obesity, common to humans and rodents.

High plasma proopiomelanocortin in aggressive adrenocorticotropin-secreting tumors.

A specific propiomelanocortin (POMC) immunoradiometric assay was developed using antibodies directed against ACTH and beta-endorphin (beta end). Partially purified standard POMC was prepared from the human small cell lung carcinoma cell line DMS-79 culture medium. Ten units (U) POMC had the same displacement ability as one pg beta end in a C-terminal beta end radioimmunoassay and thus were close if not equal to 10 pg POMC. This POMC assay was used to investigate patients with ACTH-dependent Cushing's syndrome. Plasma POMC was undetectable (< 60 U/mL) in 17 normal controls and in 4 patients with Addison's disease (concomitant ACTH plasma levels between 362 and 1058 pg/mL). Forty-two patients with Cushing's disease were studied, either before (n = 25) or after (n = 17) bilateral adrenalectomy: 7 patients with highly invasive macroadenomas had high POMC plasma levels, between 240 and 4200 U/ml (concomitant ACTH plasma levels between 77 and 5730 pg/mL); 35 patients, including one with an invasive macroadenoma, had undetectable POMC plasma levels (concomitant ACTH plasma levels between 31 and 2820 pg/mL). Among 20 patients with histologically proven ectopic ACTH syndrome, 16 had high POMC plasma levels, between 80 and 8000 U/mL (concomitant ACTH plasma levels between 45 and 9265 pg/mL); all those tumors were malignant, and the highest POMC/ACTH plasma levels ratios (taken as an index of altered POMC processing) were observed in the 3 patients with small cell carcinomas of the lung; in one of these patients, ACTH and POMC plasma levels both decreased during the course of chemotherapy, in parallel with the reduction of the tumoral mass. Four patients with ectopic ACTH syndrome had undetectable POMC plasma levels (concomitant ACTH plasma levels between 78 and 335 pg/mL): they were all typical bronchial carcinoids. These data show that high POMC plasma level is neither specific for nor constant in ectopic ACTH syndrome. Rather it should be considered as a marker of tumor aggressivity, in pituitary- and non-pituitary tumors. Its diagnostic help appears limited for the most frequent cause of occult ectopic ACTH syndrome, the typical bronchial carcinoids.

Functional analysis of the human pro-opiomelanocortin promoter in the small cell lung carcinoma cell line DMS-79.

DMS-79 is a human cell line derived from a small cell lung carcinoma (SCLC), which expresses the pro-opiomelanocortin (POMC) gene. We took it as a model in which to study the mechanism of POMC gene expression in these tumors: precursor processing is altered and gene expression is essentially unresponsive to glucocorticoids. POMC gene structure appeared normal by Southern blot analysis, indicating that gene rearrangement was not responsible for its expression in DMS-79. Indeed, using transient expression of human POMC-luciferase fusion genes in DMS-79, we showed that (1) the normal human POMC promoter was functional in DMS-79, and (2) the same proximal promoter region (-417; + 21) produced the full transcriptional activity in DMS-79 and in the mouse pituitary cell line AtT-20. Progressive 5' deletion analysis revealed differences between AtT-20 and DMS-79: region (-611; -376) was active in AtT-20 and not in DMS-79, whereas region (-95; -161) was active in both cell lines and (-376; -417) was only active in DMS-79. The latter partially overlaps a motif homologous to the DE-2 rat element which confers the tissue-specific expression of POMC in AtT-20 cells; however, this motif had no effect in DMS-79. These data suggest that POMC gene transcription is achieved through a different set of transacting factors in DMS-79 and AtT-20. Altogether, our results provide evidence that DMS-79 is a valid model of tumors responsible for the ectopic ACTH syndrome and that the mechanism of POMC gene expression in these SCLC cells is different from that in pituitary cells.

Structure of the gene for the testis-specific proprotein convertase 4 and of its alternate messenger RNA isoforms.

Proprotein convertase 4 (PC4) is a mammalian secretory serine endoproteinase similar to the yeast KEX2 gene product and specifically expressed in testicular germs cells. PC4 mRNA isoforms that vary in size and 3' coding sequence have been reported (N. G. Seitah, R. Day, J. Hamelin, A. Gaspar, M. W. Collard, and M. Chrétien, 1992, Mol. Endocrinol. 6: 1559-1570). To determine the origin of these various forms, the mouse PC4 gene was cloned and its organization determined. The structural gene is approximately 9.5 kb long. It contains 15 exons and 14 introns. The exon-intron organization is very similar to that of the genes for the related convertases furin, PC1, and PC2. The upstream region carries several GGGCGG and three CCAAT but no TATAA motifs. Analysis of the 5' end of PC4 mRNA in the testis has led to the identification of two novel 5' splice variants that might encode a nonsecretory enzyme. The multiple forms of PC4 mRNA can all be explained by alternate splicing of primary transcripts of a single gene.