The Klotho gene encodes a 130-kDa single-pass transmembrane protein with a short cytoplasmic domain (10 amino acids) and is expressed predominantly in the kidney. Mice carrying a loss-of-function mutation in the Klotho gene develop a syndrome resembling human aging, including shortened life span, skin atrophy, muscle atrophy, osteoporosis, arteriosclerosis, and pulmonary emphysema (1). Conversely, overexpression of the Klotho gene extends the life span and increases resistance to oxidative stress in mice (2-4). These observations suggest that the Klotho gene functions as an aging suppressor gene. The extracellular domain of Klotho protein is shed and secreted in the blood (2, 5), potentially functioning as a humoral factor that signals suppression of intracellular insulin/IGF1 signaling, which partly contributes to its anti-aging properties (2). However, a signaling pathway(s) directly activated by Klotho protein, including the identity of the Klotho receptor, has not been determined. The function of the transmembrane form of Klotho protein also remains to be determined.Fibroblast growth factor-23 (FGF23) 2 was originally identified as a gene mutated in patients with autosomal dominant hypophosphatemic rickets (6), where mutations in the FGF23 gene conferred resistance to inactivation by protease cleavage, resulting in elevated serum levels of FGF23 (7-12). FGF23 inhibits phosphate transport in renal proximal tubular cells and in proximal tubules perfused in vitro (13). Consistent with these findings, mice defective in FGF23 expression show increased renal phosphate reabsorption and hyperphosphatemia (14). Although FGF23 binds to multiple FGF receptors (FGFRs) (15), it has modest receptor affinity (K D ϭ 200 -700 nM) and often requires cofactors such as heparin or glycosaminoglycan (15, 16) to activate FGF signaling in cultured cells and to inhibit phosphate transport in proximal tubules perfused in vitro (13).Klotho-deficient mice (Klotho Ϫ/Ϫ mice) and FGF23 deficient mice (Fgf23 Ϫ/Ϫ mice) develop many common phenotypes, including shortened life span, growth retardation, infertility, muscle atrophy, hypoglycemia, and vascular calcification in the kidneys. Notably, they both have increased serum levels of phosphate (14, 17). These observations have led us to the hypothesis that Klotho and FGF23 may function via a common signal transduction pathway. In this report we show that Klotho binds to multiple FGFRs and functions as a cofactor necessary for FGF signaling activation by FGF23. MATERIALS AND METHODSExpression Vectors-Complementary DNA containing the mouse FGFRs coding region (IMAGE Clone, Invitrogen, supplemental Fig. 1) were cloned into pcDNA3.1(ϩ) expression vector (Invitrogen). Before subcloning, a V5-epitope tag was added to the C terminus and appropriate restriction enzyme sites to the both ends using synthetic oligonucleotides and polymerase chain reaction. Expression vectors for the mouse FGF23 resistant to proteolytic inactivation (R179Q) (18), the transmembrane form of mouse Klotho, and the extracel...

klotho is an aging suppressor gene and extends life span when overexpressed in mice. Klotho protein was recently demonstrated to function as a hormone that inhibits insulin/insulin-like growth factor-1 (IGF-1) signaling. Here we show that Klotho protein increases resistance to oxidative stress at the cellular and organismal level in mammals. Klotho protein activates the FoxO forkhead transcription factors that are negatively regulated by insulin/IGF-1 signaling, thereby inducing expression of manganese superoxide dismutase. This in turn facilitates removal of reactive oxygen species and confers oxidative stress resistance. Thus, Klotho-induced inhibition of insulin/IGF-1 signaling is associated with increased resistance to oxidative stress, which potentially contributes to the anti-aging properties of klotho.A defect in klotho gene expression in mice leads to a syndrome closely resembling human aging, including shortened life span, infertility, growth arrest, hypoactivity, skin atrophy, premature thymic involution, arteriosclerosis, osteoporosis, and pulmonary emphysema (1). Conversely, overexpression of the klotho gene extends the life span in the mouse (2), indicating that the klotho gene functions as an aging suppressor gene in mammals that delays aging when overexpressed and accelerates the development of aging-like disorders when disrupted. The klotho gene encodes a single-pass transmembrane protein and is expressed only in limited tissues, notably the distal convoluted tubules in the kidney and the choroid plexus in the brain (1). The extracellular domain of Klotho protein is shed and secreted into the blood. It then binds to a high affinity but as yet unidentified cell-surface Klotho receptor and signals suppression of tyrosine phosphorylation of insulin/ IGF-1 2 receptors and insulin receptor substrates (IRS), association of IRS with phosphatidylinositol 3-kinase (PI3K), and serine phosphorylation of Akt/PKB (2). Thus, Klotho protein is a hormone that inhibits the intracellular insulin/IGF-1 signaling cascade. This activity likely contributes to the suppression of aging by Klotho, because inhibition of insulin-like signaling is an evolutionarily conserved mechanism for extending life span (see Ref. 3 for review). Indeed, we observed alleviation of aging-like phenotypes in Klotho deficient mice (KL Ϫ/Ϫ mice) by genetic perturbation of insulin/IGF-1 signaling, indicating that the activity of Klotho that inhibits insulin/IGF-1 signaling accounts for its anti-aging properties, at least in part (2). It remains to be determined whether or not the inhibitory effect of Klotho protein on IRS, PI3K, and Akt is entirely dependent on its ability to inhibit insulin/IGF-1 receptors. Notably, single nucleotide polymorphisms in the human KLOTHO gene are associated with longevity (4) and common age-related diseases including coronary artery disease (5), osteoporosis (6 -8), and stroke (9), strongly arguing that Klotho regulates aging in humans. Increased resistance to oxidative stress is associated with increased longevi...

Advanced lower rectal cancer patients having LNI in the lateral pelvic area are likely to receive prognostic benefit from lymphadenectomy. The most efficient means of determining the effectiveness of lateral dissection preoperatively is to estimate the nodal diameter in the "vulnerable" lateral regions by diagnostic imaging.

To establish an optimal categorization of cancer deposits without lymph node structure (extranodal cancer deposits [EX]) in a prognostic staging system, we analyzed 1,027 cases in which patients underwent potentially curative surgery for advanced colorectal adenocarcinoma. EX was classified as vascular invasion-type (VAS) or non-VAS.A total of 512 foci of EX were identified in 205 patients (20.0%), with VAS and non-VAS found in 68 and 182 patients, respectively. The hazard ratio for patients with nodal involvement was 3.6 and for patients with VAS and non-VAS, 2.5 and 4.7, respectively. Based on multivariate analysis of these 3 parameters, only nodal involvement and non-VAS were significant prognosticators. By using the Akaike information criterion, N staging was capable of predicting survival outcome with the highest accuracy when both nodal involvement and non-VAS were treated together as an N factor and VAS was treated as a T factor ("new categorization"). The clinical significance of the TNM grading system for colorectal cancer would be enhanced if we treat EX as a new categorization.

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Extent of mesorectal invasion, based on a 6-mm cutoff value, is useful for subclassification of T3 rectal cancer patients.

Objective: To determine the significance of the extent of mesorectal tumor invasion as a prognostic factor for T3 rectal cancer patients. Summary Background Data: There is controversy as to which primary lesion characteristics, other than regional lymph node involvement, in T3 rectal cancer are reliable prognostic factors. Patients and Methods:The extent of mesorectal tumor invasion was evaluated using 2 data sets comprising 196 and 247 patients undergoing curative surgery at separate institutes. When the outer aspect of the muscular layer was not identifiable, an estimate was obtained by drawing a straight line between the 2 break points of the muscular layer. Results: We selected 6 mm as the optimal value for subclassification of T3 rectal patients into 2 groups, based on the extent of mesorectal invasion, using the first data set. The overall 5-year survival rate was significantly higher in patients with Ͻ6 mm than in those with Ն6 mm of mesorectal invasion (72% versus 50%; P Ͻ 0.01). Similarly, in the second data set, the overall 5-year survival rates of patients with mesorectal invasion Ͻ6 mm and Ն6 mm were 59% and 37%, respectively (P Ͻ 0.01). In both data sets, multivariate analyses verified the extent of mesorectal invasion to be an independent prognostic factor, together with nodal involvement. Regarding positive nodal involvement and mesorectal invasion Ն6 mm as risk factors, the overall 5-year survival rates with none, one, and both of these factors were 84%, 61%, and 38%, respectively, in the first data set (P Ͻ 0.01). Prognostic results were similar for the second data set. Conclusion: Extent of mesorectal invasion, based on a 6-mm cutoff value, is useful for subclassification of T3 rectal cancer patients. (Ann Surg 2006;243: 492-498)

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