Cholecystokinin (CCK) and CCK receptor expression by human gliomas:evidence for an autocrine/paracrine stimulatory loop

Cholecystokinin (CCK) is a gut-brain peptide has been described to be able to induce mitosis according to recent studies. Additionally, conflicting data has been published on whether tumours of the central and peripheral nervous system in general, and gliomas in particular, express CCK receptors. In the present in vitro study we employed reverse transcription followed by the polymerase chain reaction (RT-PCR) to investigate whether mRNA for CCK-A and CCK-B receptors as well as CCK peptide itself is present in primary human gliomas and the U-87 MG GBM cell line. The data show that 14/14 (100%) of the primary gliomas exhibited mRNA expression for the CCK peptide gene and the B receptor including the U-87 MG cells, whereas, only 2/14 (14%) showed presence of the CCK-A receptor. The presence of CCK receptors together with CCK peptide expression itself suggests presence of an autocrine loop controlling glioma cell growth. In support of this conclusion, a neutralizing antibody against the CCK peptide exhibited a dose dependent inhibition of cell growth whereas, antagonists to CCK caused a dose depend inhibition of exogenous stimulated glioma cell growth in vitro, via the CCK-B receptor which is PKC activated. Assessment of apoptosis and proteasome activity were undertaken and we report that treatment with CCK antagonists decreased proteasome and increased caspase-3 activity. These data indicate that CCK peptide and CCK-B are abundant in human gliomas and they act to stimulate cell growth in an autocrine manner, primarily via the high affinity CCK-B receptor, which was blocked by antagonists to CCK, perhaps via apoptosis.

β-catenin mutations in craniopharyngiomas and pituitary adenomas

Craniopharyngiomas and pituitary adenomas are both tumors of the hypothalamic and pituitary region, respectively that are frequently associated with endocrine defects either because of direct involvement of hormone producing cells (most pituitary tumors) or because of secondary defects due to disturbance of hypothalamic function (some pituitary tumors and craniopharyngiomas). Some studies suggest that mutant β-catenin gene cells in craniopharyngiomas and pituitary adenomas contribute to their tumorigenesis. DNA was extracted from 73 cranial tumors and subjected to polymerase chain reaction (PCR) with previously described primers encompassing glycogen synthase kinase-3β phosphorylation sites of the β-catenin gene. Sequenced PCR products for possible β-catenin gene mutations showed a total of 7/43 alterations in adamantinomatous craniopharyngioma-derived DNA samples. Two previously described β-catenin mutations in codon 33 TCT(Ser) > TGT(Cys) and codon 37 TCT(Ser) > TTT(Phe), whereas three novel mutations in codon 41 ACC(Thr) > ATC(Ile), codon 33 TCT(Ser) > TAT(Tyr) and codon 32 GAC(Asp) > AAC(Asn) were observed. None of the 22 pituitary adenomas and the eight papillary craniopharyngiomas analyzed presented any sequence alterations. These findings demonstrate an association between β-catenin gene alterations and craniopharyngiomas of the adamantinomatous type. Since this gene product is involved with development, these results suggest that β-catenin mutations may contribute to the initiation and subsequent growth of congenital craniopharyngiomas. © Springer 2005.

Meningiomas expressing and responding to cholecystokinin (CCK)

The effect of cholecystokinin (CCK) on cultured human meningioma derived cells was investigated. Exposure of meningioma cells for 6-12 days to CCK-8s (2-200 nM) resulted in a dose dependent stimulation of cell growth to a maximum of 1.1-fold over basal controls. A time course study showed stimulation of cell growth at day 3 followed by increase throughout day 6. The stimulatory effect of CCK on meningioma cell growth was completely abolished by a CCK-B specific receptor antagonist, L-365,260. Reverse-transcription of meningioma-derived RNA into cDNA followed by amplification by the polymerase chain reaction using specific primers for CCK peptide and its CCK-A and/B receptor revealed 100% presence of CCK peptide and CCK-B receptors mRNA whereas CCK-A receptor was expressed in 66% of the meningiomas. These results provide evidence that human meningioma cells possess CCK peptide and its receptors the activation of which leads to increase of cell growth possibly via an autocrine/paracrine mechanism. © Springer 2005.