Low molecular weight mitogenic factor produced by BRL-3A cultured rat liver cells

TNFα and IL-17 cooperatively stimulate glucose metabolism and growth factor production in human colorectal cancer cells

Background

Inflammation is a well-known etiological factor for colorectal cancer, but mechanisms underlying the linkage between inflammation and cancer are incompletely understood. We hypothesized that two pro-inflammatory cytokines, TNFα and IL-17, might play a role in promoting colorectal carcinogenesis. Aerobic glycolysis is a metabolic adaptation that promotes the survival/proliferation of cancer cells. Paracrine signaling between tumor cells and cancer-associated fibroblasts also plays a role in carcinogenesis.

Methods

The effect of TNFα and IL-17 on aerobic glycolysis and growth factor production in cultured human colorectal cancer cells was investigated. Glucose utilization and lactate production were quantified by measuring the disappearance of glucose and appearance of lactate in the culture medium. Glucose transporter and glycolytic enzyme expression levels were measured by immunoblotting.

Results

TNFα and IL-17 cooperatively stimulated glycolysis in HT-29, T84, Caco-2 and HCT116 colorectal cancer cells. Treatment of HT-29 cells with TNFα plus IL-17 also increased the expression of HIF-1α and c-myc, two factors know to induce the transcription of genes encoding components of the glycolytic pathway. To further investigate mechanisms for cytokine-stimulated glycolysis, the effects of TNFα and IL-17 on expression of six members and one regulator of the glycolytic pathway were investigated. TNFα and IL-17 cooperatively increased the expression of the glucose transporter SLC2A1 and hexokinase-2 but did not regulate expression of glucose transporter SLC2A3, enolase-1, pyruvate kinase M2, lactate dehydrogenase A, or 6-phoshofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3). Experiments with inhibitors indicated that HIF-1α played a role in induction of SLC2A1 and that the transcription factor NF-κB played a role in induction of hexokinase-2 by TNFα and IL-17. TNFα and IL-17 also synergistically stimulated production by HT-29 cells of a growth factor that simulated proliferation/survival of NIL8 fibroblastic cells. The activity of this factor was not specifically inhibited by the EGFR inhibitor AG1478, indicating that it is not an EGFR ligand.

Conclusions

Chronic inflammation is known to promote colorectal tumorigenesis. The pro-inflammatory cytokines TNFα and IL-17 may contribute to this effect by stimulating glycolysis and growth factor production in colorectal cancer cells.

The E-domain peptide of rat pro-insulin-like growth factor II (proIGF-II): properties of the peptide in serum and production by rat cell lines

We previously identified a naturally occurring peptide fragment derived from the carboxyl terminal region of the E-domain of pro-insulin-like growth factor II (proIGF-II117-156) in medium conditioned by cultured BRL-3A rat liver cells. In the present study we utilized a radioimmunoassay (RIA) for this peptide to measure physiological concentrations of the peptide in media and serum. Serum levels of the E-domain peptide were very high in the 5-day neonatal rat and declined thereafter to reach low levels in adult rat serum. Chromatography of adult rat serum on Sephadex G-75 in 1 M acetic acid yielded a single broad peak of E-peptide immunoreactivity that coeluted with a synthetic E-peptide standard. However, chromatography of day 5 neonatal rat serum on Sephadex G-75 yielded two peaks of immunoreactivity. One of the peaks coeluted with a synthetic E-peptide standard, whereas the other peak eluted in a region where higher molecular weight proteins typically elute. Experiments aimed at determining whether adult rat serum contained a binding protein for the E-domain peptide revealed that: (1) serum contains little, if any, binding protein for the E-domain peptide, (2) serum contains a proteinase activity that degrades the E-domain peptide, and (3) the proteinase activity can be eliminated by acetic acid/ethanol extraction. Of several rat cell lines tested (BRL-3A, rat embryo fibroblasts (REF), hepatoma cell lines (H4, HTC), GH3 pituitary tumor cells, and normal rat kidney fibroblasts (NRK], only BRL-3A and REF cells secreted measurable E-domain peptide into the medium. In addition, it was found that some component(s) of serum could stimulate secretion of E-domain peptide from BRL-3A and REF cells. Chromatography of the immunoreactivity from BRL-3A and REF-conditioned media on Sephadex G-75 in 1 M acetic acid yielded a single peak that coeluted with a synthetic E-domain peptide standard. Since secretion of the E-domain peptide parallels the expression of IGF-II, the RIA for the proIGF-II E-domain peptide may be useful for studies of the biosynthesis and secretion of IGF-II under different physiological conditions. The RIA for the IGF-II E-domain peptide has two technical advantages over the RIA for IGF-II, namely, the lack of interference by IGF binding proteins and the relative ease with which large quantities of pure antigen can be synthesized.

Growth suppression of hybrids between transformed cells and normal fibroblasts in serum-free medium: correlation with retention of human chromosomes

Somatic cell hybrids formed by crossing PG19 mouse melanoma cells with mouse embryo fibroblasts have a reduced ability to proliferate in growth factor-unsupplemented serum-free medium relative to the parental melanoma cells. The suppression of growth of the hybrid cells in serum-free medium is attributable to a strict requirement of these cells for polypeptide growth factors (insulin plus platelet-derived growth factor, fibroblast growth factor, or epidermal growth factor). In contrast, the parental melanoma cells are able to grow without exogenously added growth factors. Fifteen hybrids derived from crosses between mouse L cells and normal human skin fibroblasts also have been tested for ability to grow in growth factor-unsupplemented serum-free medium. Depending on which human chromosomes are retained, growth of these hybrids in serum-free medium is also suppressed relative to growth of the L cell parent. There appear to be several genes on different chromosomes that are involved in suppression of serum-free growth of the fibroblast x L cell hybrids. One weak suppressor gene appears to be on the human X chromosome.

Effects of bradykinin on DNA synthesis in resting NIL8 hamster cells and human fibroblasts

Bradykinin stimulates [3H]thymidine incorporation and DNA synthesis in resting, serum-deprived NIL8 hamster cells. The ED50 for this stimulation is 4.52 +/- 2.91 nM. Other kinin peptides including lys-bradykinin (kallidin) and met-lys-bradykinin also stimulate [3H]thymidine incorporation in the NIL8 cells, whereas desarg9-bradykinin is without effect, suggesting action of the kinin peptides through type B2 receptors. Bradykinin also stimulates DNA synthesis in IMR-90 human fibroblasts; however, this effect is observed only in the presence of indomethacin, which blocks prostaglandin synthesis. These results suggest that prostaglandins act as negative modulators of the growth-stimulatory effects of bradykinin in the fibroblasts. This conclusion is supported by the observation that exogenously added PGE1, PGE2, PGA1, PGA2, PGB1, and PGB2 strongly inhibit [3H]thymidine incorporation in the human fibroblasts. The direct effect of bradykinin observed in the NIL8 cells may be attributable to the relative resistance of these cells to growth inhibition by prostaglandins.

A method for culturing chick melanocytes: the effect of BRL-3A cell conditioning and related additives

A method for growing chick embryo melanocytes is described that utilizes medium conditioned by Buffalo Rat liver (BRL-3A) cells. The dissected trunk region of each 72 h (Stages 14 to 19) embryo produces approximately 200,000 melanocytes (purity, 80%) when processed and cultured for 8 d. Thus, a typical experiment involving 20 embryos would produce a total of 4 x 10(6) melanocytes. Choice of serum, serum concentration, and cell density were determined experimentally. Partially purified multiplication stimulating activity (MSA) from BRL-3A cells and insulin were also tested as medium additives. MSA was not stimulatory, whereas insulin gave a positive response in 2% but not 10 or 0% serum. The final protocol used a modified F12 medium with 10% bovine calf serum conditioned by BRL-3A cells. Cultures were fed every other day. Small colonies of cells became evident by culture Day 3 and increased rapidly to Day 5 when pigmentation became obvious. Colony size continued to increase but more slowly from Days 5 to 8, whereas pigmentation increased rapidly and maximized on Day 8. There is a factor, or factors, present in BRL-3A conditioned medium that stimulates embryonic chick melanocytes to divide preferentially over contaminating cell types. This results in cultures that can provide adequate numbers and purity for biochemical studies.