Human breast cancer MDA-MB-231 cells fail to express the neurofibromin protein, lack its type I mRNA isoform and show accumulation of P-MAPK and activated Ras.

Neurofibromin is a tumor suppressor protein, which is similar in function to the GTPase activating protein (GAP), p120GAP, in that it accelerates inactivation of Ras. Mutations in the NF1 gene cause neurofibromatosis type 1, NF1, an autosomal dominant disease with a diverse spectrum of clinical manifestations, including neurofibromas. Ras activation (GTP binding) is induced by the GTP exchange factor Sos and its inactivation is regulated through the GAPs (p120GAP and neurofibromin). Strikingly, neurofibromin was nearly absent in MB-231 human breast cancer cells and present in the remaining four cell lines studied, with higher levels in BT-474 and MB-453 than in MCF-7 and BT-20 cells, as tested with polyclonal antibodies to both the N-terminal as well as the C-terminal peptides. Coordinated with the near absence of neurofibromin, these cells also presented with much greater levels of P-MAPK and activated Ras. Further, RT-PCR analysis demonstrated the absence of expression of NF1 mRNA type I isoform only in the MB-231 cell lines. This result documents for the first time an altered NF1 expression at the protein and mRNA levels in MDA-MB-231 breast cancer cells.

Intestinal bacteria affect growth of Bacillus thuringiensis in larvae of the oriental tea tortrix, Homona magnanima diakonoff (Lepidoptera: tortricidae).

Spores and parasporal crystals of a Bacillus thuringiensis serovar aizawai were fed to fifth instar larvae of the oriental tea tortrix, Homona magnanima, that had been reared aseptically or that had been reared normally. Viable cell numbers of B. thuringiensis and other bacteria in H. magnanima larvae were estimated by homogenization of samples and dilution plating on peptone-polymyxin agar medium for B. thuringiensis cells and on nutrient agar medium for the other bacterial cells. B. thuringiensis did not grow in the larval cadavers of normally reared H. magnanima while bacteria other than B. thuringiensis grew rapidly. In contrast, B. thuringiensis within the larval cadavers of aseptically reared H. magnanima grew and increased 20 times. The bacteria other than B. thuringiensis from the sample homogenates of normally reared larvae that were fed on B. thuringiensis-treated diets had the same characteristics as the bacteria isolated from the guts of healthy H. magnanima larvae, which were putatively identified as Streptococcus spp. and Staphylococcus spp., typical intestinal bacteria of insects. The results strongly suggest that intestinal bacteria influence the growth of B. thuringiensis in the larvae.

Retinoic acid downregulates growth, fibronectin and RAR alpha in 3T3 cells: Ha-ras blocks this response and RA metabolism.

Retinoic acid (RA) reduced growth, fibronectin, and retinoic acid receptor (RAR alpha) in NIH 3T3 cells but not in cells transformed by the Ha-ras oncogene. RA lowered RAR alpha transcript and protein, increased RAR beta transcripts, and had no effect on RAR gamma. H-ras transformation downregulated RAR expression and abolished responsiveness to RA. Ha-ras-transformed cells were as active as normal NIH-3T3 cells in RA uptake but were unable to degrade it to medium oxidation product, so that, paradoxically, the resistant cells accumulated 20-30-fold as much RA as the sensitive cells. RA sensitivity/insensitivity correlated with RA metabolism/lack thereof in 15 cell lines in serum-free medium. These data suggest a relationship between RA inhibition of cell growth and intracellular RA metabolism.

Retinoic acid metabolism and inhibition of cell proliferation: an unexpected liaison.

The rationale for the use of all-trans-retinoic acid (RA) as an anticancer agent is based on its ability to inhibit growth and promote differentiation of some neoplastic cells. However, RA is not effective in all conditions of cell culture, and in some cases, it may stimulate cell growth. We used a serum-free culture system to study the effect of RA on cell proliferation. Following 2 days of RA exposure, 9 of a total of 15 cell lines showed an inhibition of cell growth (RA-sensitive), while 6 of 15 cell lines showed resistance to RA (RA-resistant cells). Metabolic studies and high-performance liquid chromatography analysis of the cell-associated and medium extracts from cells incubated with [3H]RA revealed that all nine RA-sensitive cells showed a very high activity to metabolize RA to polar metabolites found in the medium. In sharp contrast, RA-resistant cells retained about 60% of the original RA at 76 h. However, conditioned medium from the sensitive cells was without activity on the growth of sensitive and resistant cells. We conclude that a relationship exists between RA inhibition of cell growth and intracellular RA metabolism. These data may help design useful strategies in cancer therapy by retinoids and dispel the notion that RA itself is responsible for the inhibition of cell growth.

[Clinical assessment of urinary free L-fucose levels].

We measured urinary levels of free L-fucose in healthy subjects, patients with benign diseases, and patients with cancer using an automated analyzer and a newly isolated L-fucose dehydrogenase, and evaluated the clinical usefulness of the results. The values obtained were corrected for urinary creatinine as micromoles per gram of creatinine. The cutoff value, set at the mean + 2SD for the healthy subjects, was 250 mumol/g.Cr. Patients with gallbladder cancer, bile-duct cancer, liver cancer, pancreatic cancer, or cirrhosis of the liver had significantly higher levels of L-fucose than the healthy subjects. The diagnostic sensitivity for these five diseases, taken together, was 68% (144/213). Specificity for the detection of cancer was calculated by use of false positives for patients with cholelithiasis, hepatitis, and pancreatitis: it was 73% (76/104). Diagnostic accuracy for these seven diseases taken together was therefore 69% (220/317). We compared the positive ratio of the L-fucose level with that of the tumor markers AFD and CA19-9. The positive ratio of an L-fucose value above the cutoff was higher than the positive ratio of either marker in bile-duct cancer, gallbladder cancer, liver cancer, and pancreatic cancer. The results suggested that the urinary levels of free L-fucose reflected the metabolism of sugar chains of glycoconjugates, and may be usefully clinically as a tumor marker.

Dynamics of kallikreinogen under hemodialysis.

There are many complications due to hemodialysis, causes of which seem to lie under disorders of the coagulation system, fibrinolytic system, and kinin system. Therefore, it is important to understand the dynamics of these systems during hemodialysis. Accordingly, kallikreinogen, plasminogen, plasmin inhibitors, contact factor, antithrombin, and prothrombin were assayed during the experimental dialysis, experimental ultrafiltration and clinical hemodialysis. Plasmin inhibitors decreased remarkably by dialysis. They then recovered the pre-dialytic values as time went on. Kallikreinogen did not show any definite tendency immediately after the beginning of dialysis, but two hours later its value rather increased relative to thepre-dialytic value. It was supposed that this increase was caused by reactive hyperproduction due to gradual consumption of kallikreinogen. Contact factor slightly decreased by dialysis, whereas prothrombin and antithrombin decreased apparently. When hemodialysis is practiced, it is necessary to fully realize that the coagulation system, fibrinolytic system, and kinin system might lose their balance.