Purpose: We isolated a subline (CC531M) from the CC531S rat colon carcinoma cell line, which grows and metastasizes much more rapidly than CC531S. We found, using RNA expression profiling, that one of the major changes in the CC531M cell line was a 5.8-fold reduction of the chemokine CXCL5. The purpose of this study was to determine the effect of CXCL5 expression on colorectal tumor growth and metastasis. Experimental Design: CC531 clones were generated with either knockdown or restored expression of CXCL5. These clones were inoculated in the liver of rats. In addition, in two independent cohorts of colorectal cancer patients, the level of CXCL5 expression was determined and associated to clinical variables. Results: Knockdown of CXCL5 expression in CC531S resulted in rapid tumor growth and increased number of metastasis, whereas restored expression of CXCL5 in CC531M resulted in a return of the ''mild'' tumor growth pattern of the parental cell line CC531S. In vitro, no difference was found in proliferation rate between clones with either high or low expression of CXCL5, suggesting that environmental interactions directed by CXCL5 determine tumor outgrowth. Finally, the importance of our findings was established for patients with colorectal cancer. We found that low expression of CXCL5 was significantly associated with poor prognosis for colorectal cancer patients. CXCL5 showed a trend (P = 0.05) for a positive correlation with intratumoral CD8 + T-cell infiltration, suggesting a possible explanation for the observed poorer prognosis. Conclusions: Our results show that CXCL5 is important in growth and development of colorectal cancer, implicating a future role in both cancer therapy and diagnosis.Colorectal cancer is one of the three leading causes of cancerrelated death among men and women in the western world (1, 2). Despite curative surgical resection of the primary tumor, 40% to 50% of the patients ultimately die of metastases (3). Tumor growth and metastasis result from a complex cascade of biological processes. Therefore, knowing key factors in these processes is crucial to design new treatment modalities.In a previous paper, we reported the in vivo selection of an aggressive rat colorectal cell line (CC531M) from the welldescribed CC531S cell line (4, 5). The present study was initiated to identify factors that contribute to rapid growth and metastatic capacity of CC531M. In this study, we focus on the chemokine CXCL5.CXCL5 is a member of the subfamily of lipopolysacharideinducible ELR + CXC chemokines (6). It functions, mainly through interaction with the CXCR2 receptor, both as a chemoattractant and as an angiogenic factor (7 -10). CXCL5 is expressed in the epithelial cells of the colon and overexpressed in colorectal cancer (11,12). It has been reported that CXCL5 plays a role in development and metastasis of several cancer types (13 -15). CXCL5 contributes to the in vivo growth and angiogenic potential of non -small cell lung cancer. Homogenates of human non -small cell lung cancer specimens...

Isolated rat hepatocytes were incubated with extracellular ATP to induce a prolonged increase in intracellular Ca2l ([Ca2+]1) and a loss of viability within 2 h. By using video-intensified fluorescence microscopy, the effects of exposure to extracellular ATP on [Ca2-]i, mitochondrial membrane potential (MMP) and cell viability were determined simultaneously in individual living hepatocytes. The increase in [Ca2+]1 on exposure to ATP was followed by a decreasing MMP; there were big differences between individual cells. Complete loss of the MMP occurred before cell death was observed. Omission of K+ from the incubation medium decreased the cytotoxicity of ATP; under these conditions, intracellular K+ was decreased by more than 80 %. Treatment with nigericin also depleted intracellular K+ and decreased ATP-induced toxicity. Protection against loss of viability by means of a decrease in intracellular [K+] was reflected by maintenance of the MMP. These observations suggest that ATP-induced cell death may be caused by a mechanism that has been described for isolated mitochondria: after an increase in Ca2' levels, a K+ influx into mitochondria is induced, which finally disrupts the MMP and leads to cell death.

The spatio-temporal relationship between a decrease in the mitochondrial membrane potential (MMP) and externalization of phosphatidylserines (PS) during induction of apoptosis was investigated in single freshly isolated hepatocytes. Apoptosis was induced in the hepatocytes in three different ways: attack by activated Natural Killer cells, exposure to ATP, or exposure to the inhibitor of protein synthesis cycloheximide. Fluorescence microscopy showed staining of externalized PS at those areas where the staining for MMP was lost whereas in other areas the mitochondria remained intact for longer periods of time, indicating coupling between local loss of MMP and local PS exposure. To discriminate whether the decrease in MMP itself or a decrease in ATP induced PS externalization, hepatocytes were treated with rotenone, which resulted in a rapid collapse of cellular ATP but left the MMP intact for a much longer period. Addition of fructose prevented the decrease of ATP to ϳ30% and also delayed the collapse of the MMP. This indicates that ATP was needed for the maintenance of the MMP probably via reverse action of the ATP synthase. In a subsequent study hepatocytes were incubated with Natural Killer cells for induction of apoptosis followed by addition of rotenone to deplete ATP. Under these conditions the PS staining co-localized with mitochondrial MMP indicating that PS externalization does not require a collapse in MMP. Moreover, exposure of PS was evenly distributed over the whole plasma membrane. In conclusion, we propose that after an apoptotic stimulus some mitochondria start to loose their MMP, which results in cessation of ATP production and perhaps even consumption of ATP. This results in an overall decrease in cellular ATP. ATPconsuming enzyme reactions most distal from still intact mitochondria will be most sensitive to such a decrease. Apparently the translocase that keeps phosphatidylserines inward-oriented is such a sensitive enzyme.

The effect of photodynamic treatment on the yeast Kluyveromyces marxianus with aluminum‐phthalocyanines has been studied. It was found that the nonsulfonated sensitizer caused light‐dependent loss of colony‐forming capacity, whereas the mono‐ and tetrasulfonated forms did not induce loss of clonogenicity. The effect of the nonsulfonated sensitizer increased with longer preincubation periods of cells with the dye. Formation of cellattached, mostly intracellularly localized monomelic sensitizer also increased with time. The amount of cell‐bound multimeric nonsulfonated phthalocyanine did not vary with time. Experiments designed to specifically increase the amount of cell‐attached monomers led also to an increased photoinactivation of the cells. It is therefore concluded that the photodynamic effect of the nonsulfonated Al‐phthalocyanine is mediated by the monomeric form of the dye.

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Isolated rat hepatocytes were incubated with ATP to induce high intracellular free Ca2+ concentrations as determined with the Quin-2 method. Immediately after addition of ATP, the intracellular concentration of Ca2+ rose from 200 nM to more than 2.5 microM. It stayed at this value during the first 1/2 h; the rise was absolutely dependent on extracellular Ca2+. After the first 1/2 h the Ca2+ concentration decreased to 1-2 microM (5-10 times the control value). These high intracellular free Ca2+ concentrations did not lead to an immediate loss of cell viability. Only after 2 h of incubation a substantial number of cells lost viability. This was preceded by a decrease in cellular NADH (greater than 40%) and accompanied by a sharp increase in the intracellular Ca2+ concentration. Under these conditions the NADPH concentration was not affected. Cellular GSH was decreased to 30% of the initial value, but no lipid peroxidation or protein-thiol depletion was observed. Intracellular ATP, ADP and AMP were increased in the presence of extracellular ATP. Ca2+-dependent proteases seemed not to be involved in cell death. These observations are consistent with a collapse of mitochondrial functions as a final trigger of cell death.

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