Change in serum KL-6 level from baseline is useful for predicting life-threatening EGFR-TKIs induced interstitial lung disease

Background

A high incidence of interstitial lung disease (ILD) has been reported in patients with advanced non-small cell lung cancer (NSCLC) treated with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), particularly in Japanese populations. A previous report from our laboratory demonstrated that KL-6 was a useful serum biomarker to assess the severity of drug-induced pneumonitis. Based on these observations, this study was conducted to evaluate the risk factors of EGFR-TKIs induced ILD and the usefulness of monitoring serum KL-6 levels in patients who developed EGFR-TKIs induced ILD in a large multi-institutional setting.

Methods

We retrospectively reviewed clinical records and radiographies of 341 patients with advanced NSCLCs who were treated with EGFR-TKIs, and analyzed risk factors for the development of EGFR-TKIs induced ILD. Changes of circulating levels of KL-6 were also evaluated in the patients who developed EGFR-TKIs induced ILD.

Results

Among the 341 patients included in this study, 20 (5.9%) developed EGFR-TKIs induced ILD, and 9 (2.6%) died from ILD. Univariate analyses revealed that only preexisting pulmonary fibrosis was a significant risk factor for the development of EGFR-TKIs induced ILD (p = 0.003). Absolute levels of circulating KL-6 at neither baseline nor the onset of ILD could discriminate between life-threatening and non-life threatening EGFR-TKIs induced ILDs. However, we found that the ratios of serum KL-6 levels just after the onset of EGFR-TKIs induced ILD to those at baseline could quite precisely distinguish survivors from non-survivors (p = 0.006) as well as acute interstitial pneumonia (AIP) pattern from non-AIP pattern (p = 0.005).

Conclusions

The results of this study strongly support the potential of KL-6 as a diagnostic biomarker for life-threatening EGFR-TKIs induced ILD. Monitoring of KL-6 is also useful to evaluate the progression and severity of EGFR-TKIs induced ILD.     

Wnt signalling escapes to cilia

The primary cilium is proposed to restrain the level of canonical Wnt signalling, but it was unknown how the cilium achieves this. β-catenin, a component of the canonical Wnt signalling pathway, is now shown to be sequestered to the cilium by the Wnt signalling modulator Jouberin (Jbn) to restrain Wnt responses.     

B cell-activating factor controls the production of adipokines and induces insulin resistance

Visceral adipose tissue (VAT) inflammation has been linked to the pathogenesis of insulin resistance and metabolic syndrome. VAT has recently been established as a new component of the immune system and is involved in the production of various adipokines and cytokines. These molecules contribute to inducing and accelerating systemic insulin resistance. In this report, we investigated the role of B cell-activating factor (BAFF) in the induction of insulin resistance. We investigated BAFF levels in the sera and VAT of obese mice. In obese mice, the BAFF levels were preferentially increased in VAT and sera compared to these levels in normal control mice. Next, we treated mice with BAFF to analyze its influence on insulin sensitivity. BAFF impaired insulin sensitivity in normal mice. Finally, we investigated the mechanisms underlying insulin resistance induced by BAFF in adipocytes. BAFF also induced alterations in the expression levels of genes related to insulin resistance in adipocytes. In addition, BAFF directly affected the glucose uptake and phosphorylation of insulin receptor substrate-1 in adipocytes. We propose that autocrine or paracrine BAFF and BAFF-receptor (BAFF-R) interaction in VAT leads to impaired insulin sensitivity via inhibition of insulin signaling pathways and alterations in adipokine production.     

GTP Is Required for the Microtubule Catastrophe-Inducing Activity of MAP200, a Tobacco Homolog of XMAP215

Widely conserved among eukaryotes, the microtubule-associated protein 215 (MAP215) family enhances microtubule dynamic instability. The family member studied most extensively, Xenopus laevis XMAP215, has been reported to enhance both assembly and disassembly parameters, although the mechanism whereby one protein can exert these apparently contradictory effects has not been clarified. Here, we analyze the activity of a plant MAP215 homolog, tobacco (Nicotiana tabacum) MAP200 on microtubule behavior in vitro. We show that, like XMAP215, MAP200 promotes both assembly and disassembly parameters, including microtubule growth rate and catastrophe frequency. When MAP200 is added to tubulin and taxol, strikingly long-coiled structures form. When GDP partially replaces GTP, the increase of catastrophe frequency by MAP200 is strongly diminished, even though this replacement stimulates catastrophe in the absence of MAP200. This implies that MAP200 induces catastrophes by a specific, GTP-requiring pathway. We hypothesize that, in the presence of MAP200, a catastrophe-prone microtubule lattice forms occasionally when elongated but nonadjacent protofilaments make lateral contacts.Microtubules switch stochastically between growth and shortening phases, a phenomenon known as dynamic instability (Mitchison and Kirschner, 1984). Switching from a growth phase to a shortening phase is an event termed catastrophe, and, conversely, switching from shortening to growth is termed rescue. Dynamic instability is essential for the function and organization of microtubule structures, allowing microtubule arrays to explore their environment and to be remodeled rapidly. Although dynamic instability can be observed in polymers created from pure tubulin, the characteristics of the phenomenon are subject to profound regulation by microtubule-associated proteins (Howard and Hyman, 2007).In the context of regulating dynamic instability, among myriad proteins, one family, microtubule-associated protein 215 (MAP215), has been studied particularly widely (Gard et al., 2004). This family has been reported to play a major role organizing microtubule structures in many species, including: Schizosaccharomyces pombe (Ohkura et al., 1988; Garcia et al., 2001), budding yeast (Saccharomyces cerevisiae; Severin et al., 2001), Caenorhabidis elegans (Matthews et al., 1998), Xenopus laevis (Tournebize et al., 2000), Homo sapiens (Gergely et al., 2003; Cassimeris and Morabito, 2004), Drosophila melanogaster (Goshima et al., 2005), Dictyostelium discoideum (Hestermann and Graf, 2004), Aspergillus nidulans (Enke et al., 2007), and Arabidopsis (Arabidopsis thaliana; Whittington et al., 2001; Kawamura and Wasteneys, 2008). In all of these organisms, the loss-of-function phenotype can be summarized as decreased microtubule length, indicating that MAP215, as a net result, promotes microtubule assembly.Further insight into the function of MAP215 has been gained from in vitro analysis. The extent of microtubule assembly and the rate of growth are substantially increased by Xenopus XMAP215 (Gard and Kirschner, 1987) as well as by the human ortholog, TOGp (Charrasse et al., 1998). However, interestingly, analyzing parameters of dynamic instability has revealed that XMAP215 not only promotes growth rate but also promotes shortening rate and catastrophe frequency (Vasquez et al., 1994). Catastrophe-inducing activity was also demonstrated by finding that XMAP215 can disassemble GMPCPP-stabilized microtubules (Shirasu-Hiza et al., 2003). Consistent with the idea that this protein can enhance shortening, GFP-XMAP215 labeled both growing and shortening microtubule ends (Brouhard et al., 2008), and the budding yeast ortholog, stu2, analyzed in vitro, promotes catastrophe frequency as its major activity (van Breugel et al., 2003). The ability of a protein to enhance microtubule growth as well as to increase the frequency of catastrophe is paradoxical, and the mechanism for MAP215''s bipolar activity remains to be demonstrated.In plants, orthologs of MAP215, identified as MICROTUBULE ORGANIZATION1 (MOR1) in Arabidopsis (Whittington et al., 2001) and as MAP200 in tobacco (Nicotiana tabacum; Yasuhara et al., 2002) are about 70% similar to their animal counterparts, indicating strong conservation. The effects of plant MAP215 on dynamic instability have not been characterized in vitro, although a net promotion of microtubule assembly has been observed for MAP200 (Hamada et al., 2004). In living cells, analysis of dynamic instability in wild-type and mor1-1 epidermal cells revealed mor1-1 mutation increases pause duration (Kawamura and Wasteneys, 2008). However with living cells it is difficult to distinguish direct effects of the protein from indirect effects caused by the plant.Here, we characterize dynamic instability in vitro as affected by MAP200. We confirm that the plant ortholog promotes growth, catastrophes, and rescues; however, we show that, when GDP partially replaces GTP, catastrophe promotion by MAP200 is suppressed more strongly than is growth. This result suggests that MAP215 induces catastrophe by a specific, GTP-dependent mechanism. We propose a model that predicts catastrophes promoted by MAP215 are mechanistically distinct from those arising from the loss of the GTP cap.