Sending out an SOS - the bacterial DNA damage response.

The term "SOS response" was first coined by Radman in 1974, in an intellectual effort to put together the data suggestive of a concerted gene expression program in cells undergoing DNA damage. A large amount of information about this cellular response has been collected over the following decades. In this review, we will focus on a few of the relevant aspects about the SOS response: its mechanism of control and the stressors which activate it, the diversity of regulated genes in different species, its role in mutagenesis and evolution including the development of antimicrobial resistance, and its relationship with mobile genetic elements.

Symptomatic steno-occlusion of cerebral arteries and subsequent ischemic events in patients with acute ischemic stroke.

BACKGROUND: We aimed to assess the impact of symptomatic steno-occlusion (SYSO) of cerebral arteries and its characteristics on subsequent ischemic event (SIE) in patients with acute ischemic stroke. METHODS: Using a prospective stroke registry database, we identified consecutive patients with ischemic stroke who were hospitalized within 48 hours of symptom onset. SYSO denoted significant stenosis or occlusion of major cerebral arteries with ischemic lesions at the corresponding arterial territories and was characterized by its location and severity. Primary outcome was SIE that was defined as ischemic progression or recurrence within 1 year. RESULTS: In total, 1546 patients (age, 67.4 ± 13.0 years; median National Institutes of Health Stroke Scale score, 4) were enrolled in this study. The cumulative risk of SIE was 14.5% at 7 days, 14.9% at 14 days, 15.5% at 90 days, and 16.9% at 1 year. Patients with SYSO had significantly higher SIE rates compared with those without SYSO (23.0% versus 11.6%). Of the characteristics of SYSO, the location, not the severity, was significantly associated with SIE (P < .001 and P = .186, respectively). Multiple (adjusted hazard ratio, 5.85; 95% confidence interval, 1.81-18.85), intracranial internal carotid artery (ICA) (3.54; 1.21-8.21), and extracranial ICA SYSO (2.88; 1.01-8.21) raised the risk of SIE. CONCLUSIONS: Subsequent cerebral ischemic events (progression or recurrence) after an acute ischemic stroke occur mostly within several days of stroke onset and is associated with the location, but not the severity, of symptomatic steno-occlusion of cerebral arteries.

Temperature Dependency of Insect's Wingbeat Frequencies: An Empirical Approach to Temperature Correction.

This study examines the relationship between the wingbeat frequency of flying insects and ambient temperature, leveraging data from over 302,000 insect observations obtained using a near-infrared optical sensor during an eight-month field experiment. By measuring the wingbeat frequency as well as wing and body optical cross-sections of each insect in conjunction with the ambient temperature, we identified five clusters of insects and analyzed how their average wingbeat frequencies evolved over temperatures ranging from 10 °C to 38 °C. Our findings reveal a positive correlation between temperature and wingbeat frequency, with a more pronounced increase observed at higher wingbeat frequencies. Frequencies increased on average by 2.02 Hz/°C at 50 Hz, and up to 9.63 Hz/°C at 525 Hz, and a general model is proposed. This model offers a valuable tool for correcting wingbeat frequencies with temperature, enhancing the accuracy of insect clustering by optical and acoustic sensors. While this approach does not account for species-specific responses to temperature changes, our research provides a general insight, based on all species present during the field experiment, into the intricate dynamics of insect flight behavior in relation to environmental factors.

The influence of YMDD mutation patterns on clinical outcomes in patients with adefovir add-on lamivudine combination treatment.

BACKGROUND/AIM: The aim of this study was to assess the patterns of lamivudine (LAM)-resistant mutations and the influence on biochemical and virological responses to adefovir (ADV) add-on LAM combination therapy in patients with LAM-resistant chronic hepatitis B (CHB). METHODS: Seventy-eight CHB patients with confirmed genotypic resistance to LAM, who initiated ADV add-on LAM combination treatment, were enrolled at our institution between April 2007 and April 2009. RESULTS: The baseline tyrosine-methionine-aspartate-aspartate (YMDD) mutation patterns were as follows: rtM204I 45 (57.7%); and rtM204V + rtM204I/V 33 (42.3%). The decrease in the mean ± standard deviation (SD) serum log(10) HBV-DNA level did not differ between the patients carrying the rtM204I vs. rtM204IV +rtM204I/V mutations at 3, 6 and 12 months after the initiation of ADV add-on LAM combination treatment. The proportion of patients who achieved ALT normalization (<40 IU/L) 12 months after the initiation of ADV add-on LAM combination treatment were significantly higher in patients with a rtM204I mutation than rtM204V+ rtM204I/V mutations (39 [86.7%] vs. 22 [66.7%], P = 0.05). The proportion of patients in whom the log(10) HBV-DNA decreased <2 log(10) copies/ml, 6 months after the initiation of ADV add-on LAM combination treatment (non-responders), was significantly higher in patients with a rtM204V + rtM204I/V mutations than rtM204I mutation (7 [21.2%] vs. 2 [4.4%], P = 0.032). CONCLUSION: Biochemical response at 12 months from baseline was better in patients with a rtM204I mutation than rtM204V+ rtM204I/V mutations. In addition, early treatment failure was more common in patients with rtM204V+ rtM204I/V mutations than a rtM204I mutation.

Association between pre-pregnancy body mass index and socioeconomic status and impact on pregnancy outcomes in Korea.

AIM: To compare socioeconomic status and pregnancy outcomes in relation to different pre-pregnancy body mass index (BMI) levels, and to determine whether gestational weight gain is related to socioeconomic status and pregnancy outcomes. METHODS: This was a retrospective cohort study of 3554 singleton pregnancies. Gravidas were grouped into three BMI categories and in three gestational weight gain categories. We performed multivariate analyses for the associations between pre-pregnancy BMI, gestational weight gain, socioeconomic status, and pregnancy outcomes. RESULTS: Overweight gravidas had shorter gestational weeks, decreased birthweight, and increased frequency of preterm birth (P < 0.05). There were higher percentages of low levels of education and low economic status in the overweight gravidas and their husbands (P < 0.05). There were also higher percentages of low levels of education in gravidas with a low weight gain during pregnancy and their husbands, and gravidas with low weight gain had increased frequency of preterm deliveries (P < 0.05). Overweight gravidas had a higher risk for preeclampsia (adjusted OR, 2.4) and gestational diabetes (adjusted OR, 2.0). Overweight gravidas and women with excessive weight gain during pregnancy had higher risks for cesarean section (unadjusted OR, 1.6), macrosomia (unadjusted OR, 2.7) and large for gestational age (LGA) (adjusted OR, 2.4). A higher risk for small gestational age (SGA) fetuses existed in normoweight gravidas and gravidas with low weight gain during pregnancy (unadjusted OR, 2.8). CONCLUSION: Overweight gravidas were associated with low education status, low economic status, and adverse pregnancy, whereas low weight gain during pregnancy was associated with low education status of the gravida and her husband, preterm delivery, and SGA.

Comparison of postoperative voice outcomes after postauricular facelift robotic hemithyroidectomy and conventional transcervical hemithyroidectomy.

BACKGROUND: The purpose of this study was to determine whether postauricular robotic and conventional hemithyroidectomy result in significantly different voice outcomes. METHODS: We prospectively compared the voice handicap index (VHI)-10 and acoustic parameters of a postauricular facelift robotic group and a conventional group preoperatively, 1 week, 1 month, and 6 months after surgery. RESULTS: Forty-two patients in the postauricular group and 68 patients in the conventional group completed the VHI-10 questionnaire and acoustic analysis. The postoperative VHI-10 scores were not significantly different between the two groups. In female patients, the highest frequency was higher and the frequency range was wider in the postauricular group compared to the conventional group postoperatively until 1 month after surgery. CONCLUSION: Postauricular facelift robotic thyroidectomy has advantages over conventional thyroidectomy in terms of postoperative voice pitch.

Factors affecting abdominal pain during colonoscopy.

OBJECTIVE: The actual degree of pain or discomfort experienced during colonoscopy varies between patients. This prospective study was conducted to determine what variables, apart from the endoscopist's skill, are associated with a patient's discomfort during this procedure. DESIGN/METHODS: From December 2003 to September 2004, 646 colonoscopy examinations performed by three experienced endoscopists were analysed. Midazolam and meperidine were administered intravenously 10 min before the procedure. The degree of patient discomfort was assessed by asking more than five times during the procedure and by using a visual analogue pain scale (0-10) examined up to 7 days after the procedure. Patients were divided into sub-groups as follows: (1) comfortable group (n=304), no complaint during the procedure; and (2) uncomfortable group (n=342), more than one complaint during the procedure. RESULTS: The correlation between the degree of patient discomfort and the results of the visual analogue pain scale was statistically significant (r2=0.118, P<0.01). Chi-squared analyses demonstrated that female gender, younger age (480 s), technically difficult insertion, and lower body mass index (BMI) are factors associated with uncomfortable procedure. Multivariate analysis demonstrated that younger age, female gender, lower BMI, difficulty of examination, and previous gynaeco-pelvic surgery in female gender are independent factors associated with discomfort during colonoscopy. CONCLUSIONS: An uncomfortable colonoscopic procedure will be expected in younger, female patients with a history of gynaeco-pelvic surgery.

Quercetin decreases the expression of ErbB2 and ErbB3 proteins in HT-29 human colon cancer cells.

Quercetin has chemoprotective properties in experimental colon cancer models, and in vitro studies have demonstrated that quercetin inhibits HT-29 colon cancer cell growth. ErbB2 and ErbB3 receptor tyrosine kinases have been associated with the development of human colon cancer, and the expressions of both receptors are high in HT-29 cells. In this study, we assessed quercetin regulation of HT-29 and SW480 cell apoptosis and the influence of quercetin on the protein expression of ErbB2, ErbB3, Akt, Bax and Bcl-2. We cultured HT-29 cells in the presence of various concentrations (0, 25, 50, or 100 micromol/L) of quercetin or rutin. Quercetin inhibited HT-29 cell growth in a dose-dependent manner, whereas rutin had no effect on the cell growth. DNA that was isolated from cells treated with 50 micromol/L of quercetin exhibited an oliogonucleosomal laddering pattern characteristic of apoptotic cell death. Western blot analysis of cell lysates revealed that Bcl-2 levels decreased dose-dependently in cells treated with quercetin, but Bax remained unchanged. Quercetin increased levels of cleaved caspase-3 and the 89-kDa fragment of poly (ADP-ribose) polymerase. In addition, phosphorylated Akt levels were markedly lower in cells treated with 25 micromol/L quercetin, but total Akt levels decreased only at 100 micromol/L quercetin. Furthermore, a dose-dependent decrease in ErbB2 and ErbB3 levels was detected in quercetin-treated cells. The results obtained using SW480 cells were similar to those obtained with HT-29 cells. In conclusion, we have shown that quercetin inhibits cell growth and induces apoptosis in colon cancer cells, and that this may be mediated by its ability to down-regulate ErbB2/ErbB3 signaling and the Akt pathway.

4-1BBL signaling promotes cell proliferation through reprogramming of glucose metabolism in monocytes/macrophages.

Obesity-induced monocyte/macrophage proliferation and activation play a crucial role in various chronic inflammatory metabolic disorders, such as insulin resistance, diabetes mellitus, and atherosclerosis. 4-1BBL, a member of the tumor necrosis factor superfamily expressed on monocytes/macrophages, provides inflammatory signals to modulate their proliferation, survival, and cytokine release. Previously, we demonstrated that 4-1BBL signaling promotes adipose inflammation through enhancement of macrophage activation. Here, we show that 4-1BBL stimulation on monocytes/macrophages enhanced reprogramming of glucose metabolism in the cells, and that this was accompanied by cell proliferation. 4-1BBL stimulation on macrophages increased glucose uptake, transcript/protein levels of glucose transporter 1 and glycolytic enzymes, and lactate production. It also enhanced transcript levels of genes involved in the pentose phosphate pathway and lipogenesis. The 4-1BBL-induced metabolic reprogramming was mediated by AKT-mammalian target of rapamycin signaling. The effect of 4-1BBL-induced macrophage proliferation was completely abolished by 2-deoxyglucose, a glycolytic inhibitor. These findings suggest that 4-1BBL signaling promotes cell proliferation through reprogramming of glucose metabolism in monocytes/macrophages to support their energy demands and biomass production. The 4-1BBL signaling pathway may be a valid target for controlling macrophage-mediated chronic inflammation in obesity and metabolic diseases.

Opposing roles for the insulin-like growth factor (IGF)-II and mannose 6-phosphate (Man-6-P) binding activities of the IGF-II/Man-6-P receptor in the growth of prostate cancer cells.

The IGF-II/mannose 6-phosphate (Man-6-P) receptor (IGF2R) binds IGF-II and Man-6-P-bearing ligands at distinct binding sites. Analysis of IGF2R expression and function suggested that decreased IGF2R expression could partly account for the increased growth of lymph node carcinoma of the prostate (LNCaP) human prostate cancer cells observed with increasing passage in culture. However, LNCaP cells that expressed a Myc-tagged IGF2R (IGF2RMyc) proliferated more rapidly than control cells transfected with the empty vector. LNCaP cells expressing a mutant IGF2R incompetent to bind IGF-II (IGF2RMyc I/T) proliferated more rapidly than both vector-transfected cells and cells expressing the IGF2RMyc. In contrast, forced expression of IGF2RMyc in PC-3 human prostate cancer cells resulted in decreased proliferation, compared with control cells. As in LNCaP cells, PC-3 cells expressing IGF2RMyc I/T proliferated more rapidly than vector-transfected cells. The subcellular distribution and ability to internalize cell-surface IGF-II of IGF2RMyc were indistinguishable from endogenous IGF2R in PC-3 cells. These data suggest that the IGF-II- and Man-6-P-binding functions of the IGF2R have opposing activities, with respect to growth of prostate cancer cells. The magnitude of each activity in a given cell type seems to determine whether the net effect of the IGF2R on cell growth is inhibitory or stimulatory.

Dietary conjugated linoleic acid increases the mRNA ratio of Bax/Bcl-2 in the colonic mucosa of rats.

Previously we have shown that dietary conjugated linoleic acid (CLA) significantly decreased colon tumor incidence in rats injected with 1,2-dimenthylhydrazine (DMH). The present study was performed to explore the mechanisms responsible for the anticarcinogenic effect of CLA. Four groups of rats received either vehicle or intramuscular injections of DMH at the dose of 15 mg/kg body weight twice per week for 6 weeks and were fed a diet containing either 0% or 1.0% CLA ad libitum for 14 weeks. Dietary CLA decreased cellular proliferation and induced apoptosis in the colonic mucosa of both vehicle and DMH-treated rats. Mucosal levels of prostaglandin (PG) E(2), thromboxane B(2), and 1,2-diacylglycerol decreased in rats fed the 1% CLA diet, whereas cyclooxygenase-2 levels were not affected. Arachidonate content of mucosal phospholipids decreased significantly in rats fed the 1% CLA diet. Reverse transcriptase-polymer chain reaction analysis revealed that the Bax/Bcl-2 transcript ratio was significantly increased in rats fed 1% CLA. To examine whether the 1% CLA diet reduces tumor incidence, the DMH-treated rats were continuously fed the assigned diets for 30 weeks. Tumor incidence was significantly decreased in the CLA-fed group. In conclusion, our findings are consistent with the hypothesis that CLA decreases the incidence of colon cancer by decreasing cellular proliferation and inducing apoptosis of the colonic mucosa. These effects may be due in part to decreased PGE(2) levels and increased Bax/Bcl-2 ratios.

Conjugated linoleic acid inhibits DNA synthesis and induces apoptosis in TSU-Pr1 human bladder cancer cells.

BACKGROUND: Conjugated linoleic acid (CLA) has strong chemoprotective properties in experimental animal models. The insulin-like growth factor (IGF) system has been implicated as a risk factor for the development of bladder cancer. The present study examined CLA regulation of TSU-Pr1 bladder cancer cell proliferation and apoptosis and the influence of CLA on IGF-I receptor (IGF-IR) signaling. MATERIALS AND METHODS: TSU-Pr1 cells were cultured in serum-free medium with 0, 2, 5, or 10 microM CLA and/or 10 nM IGF-I. [3H]Thymidne incorporation, DNA laddering, FACS analysis, immunoprecipitation and Western blotting were performed. RESULTS: CLA decreased DNA synthesis and induced apoptosis in TSU-Pr1 cells dose-dependently. Exogenous IGF-I alone increased viable cell numbers but did not counteract growth inhibition induced by CLA. CLA decreased IGF-IR and insulin receptor substrate (IRS)-1 protein levels. In addition, CLA decreased IGF-I-induced phosphorylation of IGF-IR and IRS-1, recruitment of the p85 subunit of phosphoinositide 3-kinase to IRS-1 and phosphorylation of Akt and extracellular signal-regulated kinase-1/2. CONCLUSION: These results suggest that CLA inhibits cell proliferation and stimulates apoptosis of TSU-Pr1 cells via its inhibition of the IGF-IR signaling pathway.

Modern management of acute pancreatitis.

There is a rising incidence of acute pancreatitis in the United States. Numerous clinical prognostic scoring systems have been developed, including the BISAP score. Vigorous fluid resuscitation remains a cornerstone of early management of acute pancreatitis. Cross-sectional imaging in the early phase of evaluation has not been associated with improvement of outcomes. There is no role for prophylactic antibiotics in early management. However, there is growing emphasis on the identification and treatment of extrapancreatic infections. Enteral nutrition in severe acute pancreatitis has reduced mortality, systemic infection, and multiorgan dysfunction compared to parenteral nutrition. Conservative management consisting of percutaneous drainage and delayed surgical intervention is now favored for local complications, such as infected necrosis. These developments have contributed to improved outcomes for patients with acute pancreatitis.

Variable-angle locking screw volar plating of distal radius fractures.

Surgical treatment options for distal radius fractures are many and commonly involve volar locked plating. More recently, newer volar locking plates have been introduced to the market that allow the placement of independent distal subchondral variable-angle locking screws to better achieve targeted fracture fixation. This article reviews this new technology and presents the authors' experience with the Aptus (Medartis, Kennett Square, Pennsylvania) variable-angle volar locking plates.

Induction of cell cycle arrest and apoptosis in HT-29 human colon cancer cells by the dietary compound luteolin.

Luteolin is 3',4',5,7-tetrahydroxyflavone found in celery, green pepper, and perilla leaf that inhibits tumorigenesis in animal models. We examined luteolin-mediated regulation of cell cycle progression and apoptosis in the HT-29 human colon cancer cell line. Luteolin decreased DNA synthesis and viable HT-29 cell numbers in a concentration-dependent manner. It inhibited cyclin-dependent kinase (CDK)4 and CDK2 activity, resulting in G1 arrest with a concomitant decrease of phosphorylation of retinoblastoma protein. Activities of CDK4 and CDK2 decreased within 2 h after luteolin treatment, with a 38% decrease in CDK2 activity (P < 0.05) observed in cells treated with 40 micromol/l luteolin. Luteolin inhibited CDK2 activity in a cell-free system, suggesting that it directly inhibits CDK2. Cyclin D1 levels decreased after luteolin treatment, although no changes in expression of cyclin A, cyclin E, CDK4, or CDK2 were detected. Luteolin also promoted G2/M arrest at 24 h posttreatment by downregulating cyclin B1 expression and inhibiting cell division cycle (CDC)2 activity. Luteolin promoted apoptosis with increased activation of caspases 3, 7, and 9 and enhanced poly(ADP-ribose) polymerase cleavage and decreased expression of p21(CIP1/WAF1), survivin, Mcl-1, Bcl-x(L), and Mdm-2. Decreased expression of these key antiapoptotic proteins could contribute to the increase in p53-independent apoptosis that was observed in HT-29 cells. We demonstrate that luteolin promotes both cell cycle arrest and apoptosis in the HT-29 colon cancer cell line, providing insight about the mechanisms underlying its antitumorigenic activities.

Inhibition of colon cancer cell proliferation by the dietary compound conjugated linoleic acid is mediated by the CDK inhibitor p21CIP1/WAF1.

Our previous studies indicated that dietary conjugated linoleic acid (CLA) inhibits colon tumor cell proliferation in vitro and in vivo. To identify mechanisms by which CLA regulates growth arrest, the HT-29 human colon carcinoma cell line was treated with various physiological concentrations of CLA and analyzed by flow cytometry. We detected a dose-dependent increase in the percentage of cells arrested in G1 after CLA treatment that was accompanied by induction of the cyclin dependent kinase (CDK) inhibitor p21CIP1/WAF. CLA addition also led to increased p21 expression in HCT116 and SW480 cells, indicating that p21 induction is a general consequence of CLA treatment in colon cancer cells. Since both HT-29 and SW480 cells have mutant p53, our data indicate that p53 is not essential for induction of p21. In addition to an increase in p21 levels, HT-29 cell growth arrest was also accompanied by moderate decreases in Cyclin A, D1, E, and proliferating cell nuclear antigen (PCNA) levels. Following CLA treatment, p21 associated with and inhibited CDK4 and CDK2, and this correlated with reduced phosphorylation of retinoblastoma proteins. Increased association of p21 with PCNA was also detected. Dietary CLA inhibits cell cycle progression by inducing p21, which negatively regulates the growth promoting activities of CDK/cyclins and PCNA. These studies indicate that physiological concentrations of CLA inhibit growth of colon cancer cells with either wild-type or mutant p53, and may have therapeutic benefits in vivo.

Dietary polyunsaturated fats regulate rat liver sterol regulatory element binding proteins-1 and -2 in three distinct stages and by different mechanisms.

Male Sprague-Dawley rats, trained to consume their daily energy needs in a single 3-h meal (0900-1200 h), were used to examine the hypothesis that polyunsaturated fatty acids (PUFA) lowered the nuclear content of sterol regulatory element binding protein (SREBP)-1 and/or -2 by suppressing the proteolytic release of mature SREBP from the membrane-anchored precursor pool. The nuclear concentrations of hepatic SREBP-1 and -2 were 50 and 42% lower (P < 0.05) in rats that consumed a single PUFA-supplemented meal (i.e., 10 g fish oil/100 g fat-free diet) than in rats fed the fat-free diet alone. This was paralleled by 63 and 52% reductions in the expression of the SREBP-1 and -2 target genes, fatty acid synthase and HMG-CoA synthase, respectively; but the marked increase in the amount of precursor SREBP-1 and -2 resulting from meal ingestion was unaffected. After the consumption of a second meal of fish oil, the nuclear level of mature SREBP-1 was only 16% of that in rats fed the fat-free diet, but the amount of nuclear SREBP-2 was not different from the level in rats fed the fat-free diet. Again, the sizes of the SREBP-1 and -2 precursor pools were not reduced. A decrease in the hepatic concentration of precursor SREBP-1 did not occur until rats had consumed 5 meals of fish oil. At this point, the nuclear content of SREBP-2 was actually twofold higher (P < 0.05) in rats fed fish oil or safflower oil, but the amount of precursor SREBP-2 was unaffected. These data indicate that PUFA suppress the in vivo proteolytic release of SREBP-1 and -2, but the effect on SREBP-2 is transitory, possibly reflecting the ability of PUFA to enhance cholesterol losses via bile acid synthesis.

Conjugated linoleic acid inhibits cell proliferation and ErbB3 signaling in HT-29 human colon cell line.

Conjugated linoleic acid (CLA) has chemoprotective properties in experimental cancer models, and in vitro studies have shown that CLA inhibits HT-29 colon cancer cell growth. ErbB2 and ErbB3 have been implicated in the development of colon cancer, and both proteins are expressed at high levels in the HT-29 cell line. Activation of ErbB2/ErbB3 heterodimers is regulated by the ErbB3 ligand heregulin. To examine CLA regulation of HT-29 cell proliferation and apoptosis and the influence of CLA on the ErbB3 signaling pathway, HT-29 cells were cultured in the presence of CLA and/or heregulin. CLA inhibited DNA synthesis and induced apoptosis of HT-29 cells. Although the addition of heregulin-alpha led to an increase in cell number, it was not able to counteract the negative growth regulatory effect of CLA. Immunoprecipitation/Western blot studies revealed that CLA inhibited heregulin-alpha-stimulated phosphorylation of ErbB2 and ErbB3, recruitment of the p85 subunit of phosphoinositide 3-kinase (PI3-kinase) to the ErbB3 receptor, ErbB3-associated PI3-kinase activities, and phosphorylation of Akt. CLA decreased ErbB2 and ErbB3 mRNA and protein levels in a dose-dependent manner. In conclusion, we demonstrate that CLA inhibits cell proliferation and stimulates apoptosis in HT-29 cells and that this may be mediated by its ability to downregulate ErbB3 signaling and the PI3-kinase/Akt pathway.

Inhibition of Caco-2 cell proliferation by all-trans retinoic acid: role of insulin-like growth factor binding protein-6.

The present study examined the effects of all-trans retinoic acid (tRA) on proliferation and expression of the IGF system in Caco-2 human colon adenocarcinoma cells. tRA inhibited Caco-2 cell proliferation in a dose-dependent manner, with a 40 +/- 2% decrease in cell number observed 48 h after the addition of 1 microM tRA. Ligand blot analysis of IGFBPs in conditioned media revealed that Caco-2 cells produced three IGFBPs of M(r): 34,000 (IGFBP-2), 24,000 (IGFBP-4), and 32,000 (IGFBP-6). The concentrations of IGFBP-2 and IGFBP-4 decreased by 48 +/- 6 and 70 +/- 13%, respectively, whereas that of IGFBP-6 increased by 698 +/- 20% with 1 microM tRA. tRA decreased mRNA levels of IGFBP-2 and IGFBP-4 by 20 +/- 3 and 50 +/- 8%, respectively, whereas tRA increased IGFBP-6 mRNA by 660 +/- 20%. tRA did not alter levels of IGF-II mRNA or peptide. To examine if endogenous IGFBP-6 inhibits cell proliferation, Caco-2 cells were transfected with an IGFBP-6 cDNA expression construct or pcDNA3 vector only and stable clones were selected. Clones overexpressing IGFBP-6 grew more slowly than vector controls and achieved final densities 30-55% lower than those of vector controls. Accumulation of IGFBP-6 mRNA and concentrations of IGFBP-6 peptide in conditioned media were increased by 200-250 and 220-250%, respectively, in the IGFBP-6 clones compared with controls. Increased expression of IGFBP-6, which has a high binding affinity for IGF-II, following tRA treatment suggests that the decreased proliferation caused by tRA may result, at least in part, from IGFBP-6-mediated disruption of the IGF-II autocrine loop in these colon cancer cells.

Trans-10,cis-12-conjugated linoleic acid inhibits Caco-2 colon cancer cell growth.

A commercially available mixture of conjugated linoleic acid (CLA) isomers decreases colon cancer cell growth. We compared the individual potencies of the two main isomers in this mixture [cis-9,trans-11 (c9t11) and trans-10,cis-12 (t10c12)] and assessed whether decreased cell growth is related to changes in secretion of insulin-like growth factor II (IGF-II) and/or IGF-binding proteins (IGFBPs), which regulate Caco-2 cell proliferation. Cells were incubated in serum-free medium with different concentrations of the individual CLA isomers. t10c12 CLA dose dependently decreased viable cell number (55 +/- 3% reduction 96 h after adding 5 microM t10c12 CLA). t10c12 CLA induced apoptosis and decreased DNA synthesis, whereas c9t11 CLA had no effect. Immunoblot analysis of 24-h serum-free conditioned medium using a monoclonal anti-IGF-II antibody revealed that Caco-2 cells secreted both a mature 7,500 molecular weight (M(r)) IGF-II and higher M(r) forms of IGF-II. The levels of the higher M(r) and the mature form of IGF-II were decreased 50 +/- 3% and 22 +/- 2%, respectively, by 5 microM t10c12 CLA. c9t11 CLA had no effect. Ligand blot analysis of conditioned medium using 125I-labeled IGF-II revealed that t10c12 CLA slightly decreased IGFBP-2 production; c9t11 CLA had no effect. Exogenous IGF-II reversed t10c12 CLA-induced growth inhibition and apoptosis. These results indicate that CLA-inhibited Caco-2 cell growth is caused by t10c12 CLA and may be mediated by decreasing IGF-II secretion in Caco-2 cells.