The nuclear receptor peroxisome proliferator-activated receptor ␦ [PPAR␦/␤ (NR1C2)] has been implicated in colorectal carcinogenesis by various molecular genetic observations. These observations have recently been supported by studies of activation of PPAR␦ by pharmacological agents. Here we present the first report of the stimulation of breast and prostate cancer cell growth using PPAR␦ selective agonists. Activation of PPAR␦ with compound F stimulated proliferation in breast (T47D, MCF7) and prostate (LNCaP, PNT1A) cell lines, which are responsive to sex hormones. Conversely, we have found that several steroid-independent cell lines, including colon lines, were unresponsive to compound F. These findings were confirmed with an additional high-affinity PPAR␦ agonist, GW501516. Conditional expression of PPAR␦ in MCF7 Tet-On cells resulted in a doxycycline-enhanced response to GW501516, thus providing direct genetic evidence for the role of PPAR␦ in the proliferative response to this drug. Activation of PPAR␦ in T47D cells resulted in increased expression of the proliferation marker Cdk2 and also vascular endothelial growth factor ␣ (VEGF␣) and its receptor, FLT-1, thus, suggesting that PPAR␦ may initiate an autocrine loop for cellular proliferation and possibly angiogenesis. Consistent with this hypothesis, we demonstrated a pro-proliferative effect of GW501516 on human umbilical vein endothelial cell cultures and found that GW501516 also regulated the expression of VEGF␣ and FLT-1 in these cells. Our observations provide the first evidence that activation of PPAR␦ can result in increased growth in breast and prostate cancer cell lines and primary endothelial cells and supports the possibility that PPAR␦ antagonists may be of therapeutic value in the treatment of breast and prostate cancer.

BackgroundPolymorphisms affecting Toll-like receptor (TLR) structure appear to be rare, as would be expected due to their essential coordinator role in innate immunity. Here, we assess variation in TLR4 expression, rather than structure, as a mechanism to diversify innate immune responses.Methodology/Principal FindingsWe sequenced the TLR4 promoter (4,3 kb) in Swedish blood donors. Since TLR4 plays a vital role in susceptibility to urinary tract infection (UTI), promoter sequences were obtained from children with mild or severe disease. We performed a case-control study of pediatric patients with asymptomatic bacteriuria (ABU) or those prone to recurrent acute pyelonephritis (APN). Promoter activity of the single SNPs or multiple allelic changes corresponding to the genotype patterns (GPs) was tested. We then conducted a replication study in an independent cohort of adult patients with a history of childhood APN. Last, in vivo effects of the different GPs were examined after therapeutic intravesical inoculation of 19 patients with Escherichia coli 83972. We identified in total eight TLR4 promoter sequence variants in the Swedish control population, forming 19 haplotypes and 29 genotype patterns, some with effects on promoter activity. Compared to symptomatic patients and healthy controls, ABU patients had fewer genotype patterns, and their promoter sequence variants reduced TLR4 expression in response to infection. The ABU associated GPs also reduced innate immune responses in patients who were subjected to therapeutic urinary E. coli tract inoculation.ConclusionsThe results suggest that genetic variation in the TLR4 promoter may be an essential, largely overlooked mechanism to influence TLR4 expression and UTI susceptibility.

Toll-like receptor (TLR) 4 is essential for the defense against infection with gram-negative pathogens, but reduced TLR4 expression has not been linked to altered disease susceptibility in humans. In mice, Tlr4 controls the mucosal response to Escherichia coli urinary tract infections. Inactivation of mouse Tlr4 causes an asymptomatic carrier state resembling asymptomatic bacteriuria (ABU). The present study compared neutrophil TLR4 expression levels between children with ABU ( ) and age-matched control subjects ( ), and n p 17 n p 24 significantly lower levels were detected in the patients with ABU. We also found elevated levels of the TLR4 adaptor protein TRIF and reduced levels of the TLR4-inhibitor SIGIRR in the patients with ABU, but MyD88 and TRAM levels were not significantly altered. Altered TLR4 and adaptor protein expression might impair TLR4 signaling and explain the weak mucosal response to urinary tract infection in patients who develop ABU rather than symptomatic disease.Urinary tract infections (UTIs) are so common and so complex that a molecular basis for disease susceptibility may appear unlikely. Yet there are marked individual differences in susceptibility, as shown by the clinical manifestations of disease [1]. Some patients develop severe, sometimes life-threatening infections, but in at least 1% of all UTI cases bacteria establish a carrier state called "asymptomatic bacteriuria" (ABU) [2,3]. The difference in disease severity is partly due to the virulence properties of the infecting Escherichia coli strain, but a lack of virulence factors alone does not explain why patients with ABU develop persistent infection without symptoms [4,5]. The present study proposes that ABU might develop as a result of reduced Toll-like receptor (TLR) 4 expression.Determinants of host susceptibility have been identified in the murine UTI model [4,6]. Innate immunity controls susceptibility to acute infection, and TLR4 signaling is especially essential for the mucosal defense, whereas adaptive immunity is less important [7][8][9]. The crucial role played by Tlr4 in the urinary tract defense was first implied in studies in C3H/HeJ mice [9]; due to a point mutation in the Toll/interleukin (IL)-1 receptor (TIR) domain, Tlr4 signaling is inactivated in these mice [10], which develop an asymptomatic carrier state resembling human ABU [9]. Tlr4 Ϫ/Ϫ mice develop a similar ABU-like state, suggesting that abrogated TLR4 signaling might protect the host from symptomatic infection [11]. TLR signaling is modified by adaptor proteins such as TIR domain-containing adaptor inducing interferon [IFN]-b (TRIF), TIR domain-containing adaptor inducing IFN-b-related adaptor molecule (TRAM), myeloid differentiation factor 88 (MyD88), and TIR domain-containing adaptor protein (TIRAP) [12][13][14][15]. In

BackgroundFor unknown reasons, urinary tract infections (UTIs) are clustered in certain individuals. Here we propose a novel, genetically determined cause of susceptibility to acute pyelonephritis, which is the most severe form of UTI. The IL-8 receptor, CXCR1, was identified as a candidate gene when mIL-8Rh mutant mice developed acute pyelonephritis (APN) with severe tissue damage.Methods and FindingsWe have obtained CXCR1 sequences from two, highly selected APN prone patient groups, and detected three unique mutations and two known polymorphisms with a genotype frequency of 23% and 25% compared to 7% in controls (p<0.001 and p<0.0001, respectively). When reflux was excluded, 54% of the patients had CXCR1 sequence variants. The UTI prone children expressed less CXCR1 protein than the pediatric controls (p<0.0001) and two sequence variants were shown to impair transcription.ConclusionsThe results identify a genetic innate immune deficiency, with a strong link to APN and renal scarring.