Somatostatin analogs in the diagnosis and treatment of cancer

Over the past few years, significant progress has been made in our understanding of the biology and functional significance of somatostatin receptors (sst) on human tumors. Somatostatin analogs, such as octreotide, bind predominantly to sst₂ and successfully control hormone hypersecretion in patients with acromegaly, islet cell tumors and carcinoids, and (temporary) control of tumor growth is often also seen. Furthermore, sst₂ on tumors can be imaged in vivo after the injection of radionuclide-coupled octreotide. Targeted chemo- and radiotherapy, in which somatostatin analogs coupled to a chemotherapeutic agent or a radionuclide are selectively internalized by sst-positive tumors, are now being studied for their effect on tumor growth. Knowledge about the differential anti-tumor effects of the sst subtypes on tumor cells might have clinical significance after the development of new subtype-specific somatostatin analogs.     

Desensitization and resensitization of rat pituitary tumor cells in long-term culture to the effects of the somatostatin analogue SMS 201-995 on cell growth and prolactin secretion

Cultured cells, prepared from the transplantable rat prolactin (rPRL)-secreting rat pituitary tumor 7315b were found to be inhibited in a dose-dependent way in their cell growth and hormone secretion by the somatostatin analogue SMS 201-995 (Sandostatin). In short-term (1 week) experiments these effects were not time dependent and of similar magnitude (an inhibition of approximately 50% at 100 nM SMA 201-995) both for the rate of rPRL secretion and for the rate of incorporation of tritiated thymidine into the tumor cells. When freshly isolated 7315b cells were used for long-term experiments (38 days), continuous exposure to SMS 201-995 at all concentrations tested (0.1 nM, 10 nM, and 1 microM) resulted in desensitization of the cells to the peptide with respect to rPRL secretion. Using a stable cell line derived from the long-term experiment and designated 7315c, we show that (a) long-term exposure of 7315c cells to SMS 201-995 leads to loss of sensitivity with respect to both rPRL secretion and cell growth, (b) this loss of sensitivity is accompanied by complete disappearance of the somatostatin receptors from the cells, (c) withdrawal of treatment from desensitized cells leads to reappearance of receptors and of sensitivity to SMS 201-995, showing that selection for a non-receptor-bearing population was not the cause of desensitization, and (d) since these experiments were carried out with a pure population of 7315c cells the effects of SMS 201-995 are direct effects on these cells and not effects mediated by other cell or organ systems.     

Differential responses of granulosa cells from small and large follicles to follicle stimulating hormone (FSH) during the menstrual cycle and acyclicity: effects of tumour necrosis factor-alpha

This study determined effects of follicle stimulating hormone (FSH) alone and in combination with tumour necrosis factor (TNF), on granulosa cells from small (5-10 mm diameter) and large (>10-25 mm) follicles during follicular and luteal phases of the cycle and during periods of acyclicity. Granulosa cells were collected from ovaries of premenopausal women undergoing oophorectomy. The cells were cultured with human FSH (2 ng/ml) and testosterone (1 microM) in the presence or absence of human TNF-alpha (20 ng/ml). Media were removed at 48 and 96 h after culture and progesterone, oestradiol and cAMP in media were measured by radioimmunoassays. FSH stimulated the accumulation of oestradiol from granulosa cells of small follicles during the follicular and luteal phases but not during acyclicity; and TNF reduced oestradiol accumulation in the presence of FSH. Interestingly, in granulosa cells from small follicles, progesterone and cAMP secretion increased in response to FSH and neither was affected by TNF. Thus, TNF specifically inhibited the conversion of testosterone to oestradiol in granulosa cells from small follicles. FSH stimulated oestradiol production by granulosa cells of large follicles obtained only during the follicular phase of the cycle and TNF inhibited the FSH-induced oestradiol secretion. Granulosa cells obtained from large follicles during the luteal phase and during acyclicity did not accumulate oestradiol in response to FSH. However, FSH increased progesterone and cAMP secretion by granulosa cells obtained from large follicles during the follicular and luteal phases. During the luteal phase alone, TNF in combination with FSH increased progesterone accumulation above that of FSH alone. FSH did not increase progesterone, oestradiol or cAMP secretion by granulosa cells obtained from large follicles during acyclicity. Thus, FSH increases progesterone, oestradiol and cAMP secretion by granulosa cells of small follicles during the follicular and luteal phases and TNF appears to inhibit FSH-induced oestradiol secretion specifically in those cells. In large follicles, FSH- stimulated granulosa cell secretion of oestradiol is limited to the follicular phase and this effect can be inhibited by TNF. In addition, when granulosa cells of large follicles do not increase oestradiol secretion in response to FSH, TNF stimulates progesterone secretion.      

Effects of fasting and pegvisomant on the GH‐releasing hormone and GH-releasing peptide-6 stimulated growth hormone secretion

OBJECTIVE: Pegvisomant is a mutated GH molecule which prevents functional dimerization and subsequent activation of the growth hormone receptor. Pegvisomant and fasting both lead to GH resistance. DESIGN AND PATIENTS: We performed a double-blind placebo-controlled cross-over study comparing the effects of pegvisomant and fasting on the GH-releasing hormone (GHRH)- and GH-releasing peptide-6 (GHRP-6)-stimulated GH-release before and after 3 days of fasting in 10 healthy lean male subjects. We also performed a single-arm open label study under nonfasting conditions in five of these subjects. On day 1, in random order, at 0800 h, a GHRP-6 or GHRH test was performed. At 1600 h, a GHRH (if the first test was a GHRP-6 test) or GHRP-6-test (if the first test was a GHRH test) was done. After the second test either pegvisomant (80 mg as a single subcutaneous injection) or placebo was administered. On day 4, GHRP-6 and GHRH tests were performed in the same order as on day 1. During the cross-over study, subjects fasted from 2400 h on day 1 until the end of the study. MEASUREMENTS: During the GH stimulation tests, blood samples were drawn every 15 min from 15 to 120 min. GH was determined in all samples. Total insulin-like growth factor (IGF)-I and free IGF-I were determined from the samples at 0 min only. RESULTS: Three days of fasting alone and pegvisomant alone as well as in combination increased GH concentrations, whereas a decrease in serum-free, but not total, IGF-I concentrations was observed. On day 4, fasting and pegvisomant, either alone or in combination, significantly increased GH concentrations after GHRH compared to baseline. Pegvisomant alone did not increase GH concentrations after GHRP-6 administration. Fasting alone increased GH levels after GHRP-6 administration. The combination of fasting and pegvisomant had a synergistic effect on GH release after GHRP-6. CONCLUSION: These human in vivo data suggest that: (1) circulating free IGF-I, and not total IGF-I, is the major component in the negative feedback on GH secretion; (2) increased pituitary GHRH receptor expression plays a role in the mechanism whereby fasting leads to increased GH concentrations; (3) in vivo, GHRP-6 sensitivity seems to be regulated primarily by metabolic factors and not by changes in GH-IGF-I axis.     

Chromosomal instability predicts metastatic disease in patients with insulinomas

Endocrine pancreatic tumors (EPTs) comprise a highly heterogeneous group of tumors with different clinical behavior and genetic makeup. Insulinomas represent the predominant syndromic subtype of EPTs. The metastatic potential of insulinomas can frequently not be predicted using histopathological criteria, and also molecular markers indicating malignant progression are unreliable because of the small number of cases per subtype studied so far. For the identification of reliable indicators of metastatic disease, we investigated 62 sporadic insulinomas (44 benign and 18 tumors with metastases) by means of comparative genomic hybridization (CGH). In addition, the role of MEN1 (multiple endocrine neoplasia type 1) gene mutations was determined to assess specific chromosomal alterations associated with dysfunction of this endocrine tumor-related tumor suppressor gene. Only one case with a somatic MEN1 mutation was identified (1527del7bp), indicating that the MEN1 gene plays a minor pathogenic role in sporadic insulinomas. CGH analysis revealed that the total number of aberrations per tumor differs strongly between the benign and the malignant group (4.2 vs 14.1; P<0.0001). Furthermore, chromosome 9q gain was found to be the most frequent aberration in both benign and malignant insulinomas, whereas chromosome 6q losses and 12q, 14q and 17pq gains are strongly associated with metastatic disease. Our study shows that chromosomal instability, as defined by > or =5 gains together with > or =5 losses, or total number of gains and losses > or =8, rather than parameters such as tumor size and proliferation index, is the most powerful indicator for the development of metastatic disease in patients with sporadic insulinoma.     

Dopamine receptor expression and function in human normal adrenal gland and adrenal tumors

Dopamine is known to play a role in the modulation of aldosterone and catecholamine secretion from the adrenal gland, where dopamine receptors (DR), in particular the DR type 2 (D(2)), have been found to be expressed. DR expression has also been demonstrated in some types of benign adrenal tumors. The aims of the current study were to evaluate DR expression and D(2) localization in the normal adrenal gland and in different types of benign and malignant adrenal tumors, as well as to evaluate the in vitro effects of the dopamine agonists bromocriptine and cabergoline on hormone secretion in nontumoral adrenal cells. Adrenal tissues from 25 patients, subjected to adrenal surgery for different diseases, were studied. These included three normal adrenals; five adrenal hyperplasias; four aldosterone-secreting, two cortisol-secreting, and two clinically nonfunctioning adrenal adenomas; two aldosterone-secreting, two cortisol-secreting, and two androgen-secreting adrenal carcinomas; and three pheochromocytomas. In all tissues, DR and D(2) isoform (D(2long) and D(2short)) expression was evaluated by RT-PCR. D(2) localization was also evaluated by immunohistochemistry using a specific polyclonal antibody, whereas D(2)-like receptor expression was evaluated by receptor-ligand binding study, using the radiolabeled D(2) analog (125)I-epidepride. The effects of bromocriptine and cabergoline on baseline and ACTH and/or angiotensin II-stimulated aldosterone, cortisol, and androstenedione secretion were evaluated in cell cultures derived from five different adrenal hyperplasia.At RT-PCR, both D(1)-like and D(2)-like receptors were expressed in all normal and hyperplastic adrenals. D(2) and D(4) were expressed in aldosterone- and cortisol-secreting adenomas, cortisol-secreting carcinomas, and clinically nonfunctioning adenomas, whereas no DR was expressed in aldosterone- and androgen-secreting carcinomas. D(2), D(4), and D(5) were expressed in pheochromocytomas. In all D(2)-positive tissues, both D(2) isoforms were expressed, with the exception of one case of aldosterone-secreting adenoma and the cortisol-secreting carcinomas, in which only the D(2long) isoform was expressed. D(2)-like receptor expression was confirmed at receptor-ligand binding study. At immunohistochemistry, D(2) was mainly localized in the zona glomerulosa and reticularis of the adrenal cortex and, to a lesser extent, in the zona fasciculata and medulla of normal and hyperplastic adrenal tissue. In the positive tumors, D(2) was localized in the tumoral cells. At the in vitro study, a significant inhibition of both baseline and ACTH-stimulated aldosterone secretion was found after high-dose cabergoline, but not bromocriptine, administration; and a significant inhibition of angiotensin-II-stimulated aldosterone secretion was found after both bromocriptine and cabergoline administration in the adrenal hyperplasias. In conclusion, the current study demonstrated that both D(1)-like and D(2)-like receptors are expressed in the normal adrenal gland and in a percentage of adrenal adenomas or carcinomas. Bromocriptine and cabergoline induce only a minor inhibition of the secretion of adrenal hormones in the nontumoral adrenal gland in vitro, not excluding, however, the possible effective use of dopamine agonists in vivo in the treatment of adrenal tumors.     

Keuskamp and the Amsterdam Infant Ventilator

At the First International Symposium on the History of Modern Anaesthesia (1982), Professor Keuskamp mentioned that the introduction of breathing machines for lung ventilation during operations had taken over 'the tiresome handwork of ventilation'. This paper traces some aspects of Keuskamp's professional career and his role in the development of the Amsterdam Infant Ventilator. In 1974, Urban and Weitzner from the State University of New York reported that the ventilator was a reliable and effective constant-volume paediatric ventilator. Other clinicians from the United States and Europe echoed this satisfactory clinical evaluation. At present, this paediatric ventilator is still in use for the initial ventilation of small infants and for the mechanical ventilation of different animal species in a variety of experimental settings.