We recently demonstrated that human bronchial epithelial cells (HBEC) constitutively express the CXC chemokine receptor CXCR3, which when activated, induces directed cell migration. The present study in HBEC examined the relative expression of the CXCR3 splice variants CXCR3-A and -B, cell cycle dependence of CXCR3 expression, and the effects of the CXCR3 ligand, the interferon-gamma-inducible CXC chemokine I-TAC/CXCL11, on DNA synthesis and cell proliferation. Both CXCR3-A and -B mRNA, assessed by real-time RT-PCR, were expressed in normal HBEC (NHBEC) and the HBEC line 16-HBE. However, CXCR3-B mRNA was 39- and 6-fold greater than CXCR3-A mRNA in NHBEC and 16-HBE, respectively. Although most HBEC (>80%) assessed by flow cytometry and immunofluorescence microscopy contained intracellular CXCR3, only a minority (<40%) expressed it on the cell surface. In this latter subset of cells, most (>75%) were in the S + G(2)/M phases of the cell cycle. Stimulation of CXCR3 with I-TAC enhanced thymidine incorporation and cell proliferation and increased p38 and ERK1/2 phosphorylation. These data indicate that 1) human airway epithelial cells primarily express CXCR3-B mRNA, 2) surface expression of CXCR3 is largely confined to the S + G(2)/M phases of the cell cycle, and 3) activation of CXCR3 induces DNA synthesis, cell proliferation, and activation of MAPK pathways. We speculate that activation of CXCR3 exerts a mitogenic effect in HBEC, which may be important during airway mucosal injury in obstructive airway diseases such as asthma and chronic obstructive pulmonary disease.

Cancer cells re-program cellular metabolism to maintain adequate nutrient pools to sustain proliferation. Moreover, autophagy is a regulated mechanism to breakdown dysfunctional cellular components and recycle cellular nutrients. However, the requirement for autophagy and the integration in cancer cell metabolism is not clear in colon cancer. Here we show a cell-autonomous dependency of autophagy for cell growth in colorectal cancer. Loss of epithelial autophagy inhibits tumor growth in both sporadic and colitis associated cancer models.Genetic and pharmacological inhibition of autophagy inhibits cell growth in colon cancerderived cell lines and patient-derived enteroid models. Importantly, normal colon epithelium and patient-derived normal enteroid growth was not decreased following autophagy inhibition. To couple the role of autophagy to cellular metabolism, a cell culture screen in conjunction with metabolomic analysis was performed. We identified a critical role of autophagy to maintain mitochondrial metabolites for growth. Loss of mitochondrial recycling through inhibition of mitophagy hinders colon cancer cell growth. These findings have revealed a cell-autonomous role of autophagy that plays a critical role in regulating nutrient pools in vivo and in cell models and provides therapeutic targets for colon cancer.

The CXC chemokines, IP-10/CXCL10 and IL-8/CXCL8, play a role in obstructive lung disease by attracting Th1/Tc1 lymphocytes and neutrophils, respectively. Inhaled corticosteroids (ICS) and long acting beta 2-agonists (LABA) are widely used. However, their effect(s) on the release of IP-10 and IL-8 by airway epithelial cells are poorly understood. This study examined the effects of fluticasone, salmeterol, and agents which raise intracellular cAMP (cilomilast and db-cAMP) on the expression of IP-10 and IL-8 protein and mRNA. Studies were performed in cultured human airway epithelial cells during cytokine-stimulated IP-10 and IL-8 release. Cytokine treatment (TNF-alpha, IL-1beta and IFN-gamma) increased IP-10 and IL-8 protein and mRNA levels. Fluticasone (0.1 nM to 1 microM) increased IP-10 but reduced IL-8 protein release without changing IP-10 mRNA levels assessed by real time RT-PCR. The combination of salmeterol (1 micro M) and cilomilast (1-10 mu M) reduced IP-10 but had no effect on IL-8 protein. Salmeterol alone (1 micro M) and db-cAMP alone (1 mM) antagonised the effects of fluticasone on IP-10 but not IL-8 protein. In human airway epithelial cells, inhibition by salmeterol of fluticasone-enhanced IP-10 release may be an important therapeutic effect of the LABA/ICS combination not present when the two drugs are used separately.

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