Allelic imbalance at the LKB1 (STK11) locus in tumours from patients with Peutz-Jeghers' syndrome provides evidence for a hamartoma–(adenoma)–carcinoma sequence

Patients with Peutz-Jeghers' syndrome (PJS) develop hamartomatous gastrointestinal polyps and characteristic pigmentation, as a result of germline mutations in the LKB1 gene. The hamartomas in PJS were long considered to be without malignant potential. There is, however, accumulating epidemiological evidence to suggest that PJS predisposes to cancers at several different sites (colon, pancreas, breast, ovary, testis, and cervix), although large enough patient samples are rarely available to prove this. Allelic imbalance [allele loss, loss of heterozygosity (LOH)] has previously been reported in a small number of PJS polyps, suggesting that LKB1 acts as a tumour suppressor in these tumours. This study confirms allelic loss at LKB1 in PJS polyps and shows that LOH also occurs in cancers of the colon, breast, and cervix in PJS patients. Allele loss was additionally found in a colonic adenoma from a PJS patient, strongly suggesting the existence of a hamartoma–(adenoma)–carcinoma sequence in tumourigenesis. These results provide molecular evidence that PJS patients are predisposed to cancers at several sites, as a direct result of selection for loss of the ‘wild-type’ LKB1 allele in tumours. Given the rare involvement of LKB1 in sporadic cancers, these data also suggest that the indirect effect on cancer risk (or ‘bystander effect’) proposed for hamartomas in juvenile polyposis does not apply to carcinomas in PJS. Copyright © 1999 John Wiley & Sons, Ltd.     

Different effects of dynorphin A on in vitro guinea pig hippocampal CA3 pyramidal cells with various degrees of paired-pulse facilitation

We investigated the effects of dynorphin A (Dyn A), a heptadecapeptide, on the population spikes of the guinea pig hippocampal CA3 pyramidal neurons, in vitro, using paired-pulse stimulation of the mossy fibers. Dyn A produced facilitatory and inhibitory effects on the population spikes in the preparations with lower and higher degrees of paired-pulse facilitation, respectively. Morphine and D-Ala2, D-Leu5-en-kephalin, mu- and delta-agonist, respectively, predominantly potentiated the population spikes, while kappa-agonists such as U-50, 488H and bremazocine mainly caused an inhibition. These results suggest that Dyn A has two separate (excitatory and inhibitory) effects on the guinea pig hippocampal CA3 neurons through mu-(delta) and kappa-opioid receptors, respectively.     

Interleukin-2 activated microglia engulf tumor infiltrating T cells in the central nervous system

Interleukin-2 (IL-2) has been utilized to treat cancer patient. However, recent studies disclosed that IL-2 induces T cell death. To clarify IL-2 induced T cell apoptosis at tumor sites in the central nervous system (CNS), we utilized an intracranial implantation of IL-2 cDNA transduced murine tumor cells and examined freshly recovered tumor infiltrating T lymphocytes (TIL) with a magnetic beads separation method. CD8(+) TIL recovered from the IL-2 therapy model had three times more apoptosis than a control group, tumor weights at day 12 decreased (0.016 versus 0.041 g/mouse) and the number of TIL per gram of tumor tissue increase more than six times by IL-2 therapy (5.69x10(6) versus 33.7x10(7) cells per mouse). In addition, both activation marker expressions (CD25 and CD69) and cytokine message levels (interferon gamma, and tumor necrosis factor alpha) on CD8(+) TIL decrease in the IL-2 therapy model. Moreover, we detected higher CD8beta message levels in purified tumors associated with F4/80(+) cells from the IL-2 model than the control by a one-step RT-PCR method. Finally, we observed many CD8beta(+) TIL surrounded by numerous infiltrating F4/80(+) cells in the tumor tissues of the IL-2 therapy model by immuno-fluorescence microscopic analysis. Our data show that IL-2 sensitization of apoptosis induction for CD8(+) TIL occurred and the apoptotic T cells were eliminated by F4/80(+) microglia in the CNS. Moreover, this is the first report describing in situ elimination of TIL by F4/80(+) phagocytic cells in the CNS.     

Ruthenium red and magnesium ion partially inhibit silver ion-induced release of calcium from sarcoplasmic reticulum of frog skeletal muscles

Effects of Ca2+-induced Ca2+ release blockers, ruthenium red (RR) and Mg2+, on Ag+-induced Ca2+ release were studied using skinned muscle fibers or fragmented heavy SR (HSR) prepared from frog muscle, and compared with those on caffeine-induced one. Exposure of the skinned fibers to 5 microM Ag+ produced a rapid and large contraction in the presence of 0.043 mM free Mg2+. When Mg2+ concentration was increased to 0.86 mM, Ag+ led to a large transient contraction, combined with a small tonic one. The transient component was completely blocked by high Mg2+ (3.64 mM), but the tonic one was not. Ca2+-ATPase activity was not stimulated by increase of Mg2+ from 0.86 to 3.64 mM. Ag+ and caffeine induced a rapid Ca2+ efflux from HSR in a dose-dependent manner. RR over a range from 1 to 10 microM dose-dependently inhibited the Ca2+ efflux induced by 10 microM Ag+. Despite increase of RR to 30 microM, however, further inhibition of the Ca2+ efflux was not produced any more (77.8 +/- 12.2% inhibition). A 10 mM caffeine-induced efflux of Ca2+ was blocked slightly by only 0.5 microM RR and almost completely by 3 microM. A slight inhibition (about 28%) of the Ca2+-ATPase activity was observed in the presence of 10 microM Ag+ in 0.5 mg SR protein/ml of medium. RR and caffeine did not affect the enzyme activity. These results indicate that frog SR could induce a rapid release of Ca2+ upon Ag+ and caffeine, suggesting that Ag+ may have two different binding sites to release Ca2+; one is on Ca2+-induced Ca2+ release channel and the other on RR-insensitive site.