XIAP impairs mitochondrial function during apoptosis by regulating the Bcl-2 family in renal cell carcinoma.

Efficient apoptosis requires Bcl-2 family-mediated mitochondrial outer membrane permeabilization (MOMP), which releases pro-apoptotic proteins to the cytosol, activating apoptosis and inhibiting X-linked inhibitor of apoptosis protein (XIAP). XIAP is a member of the inhibitors of apoptosis protein family whose expression is elevated in many cancer types and participates in the release of pro-apoptotic proteins. To explore the association between XIAP and the Bcl-2 family, and the influence of XIAP on mitochondria, RNA interference of XIAP was performed in Caki-1 cells and the dynamic change in the levels of related proteins was compared with the original Caki-1 cells upon induction of apoptosis. Upon knockdown of XIAP, the release of cytochrome c (Cyt-c), second mitochondria-derived activator of caspase (Smac) and apoptotic protease activating factor 1 (Apaf-1) from mitochondria proceeded normally, whereas in Caki-1 cells, the release of these pro-apoptotic proteins was significantly prolonged, and incomplete. Downregulation of XIAP through small interfering RNA resulted in an increase of apoptosis and a marked decrease in Bcl-2 and Bcl-xl levels at 3 h. Additionally, the regulation of the level of XIAP protein affected the specific ratios of Bcl-2/Bax and Bcl-xl/Bax, which play decisive roles in cell death. In the present study, it was revealed that XIAP can feed back to mitochondria, delaying Cyt-c and Apaf-1 release. Furthermore, XIAP can limit the release of its inhibitor Smac with the involvement of Bcl-2 family proteins.

Potential biological process of X-linked inhibitor of apoptosis protein in renal cell carcinoma based upon differential protein expression analysis.

The X-linked inhibitor of apoptosis protein (XIAP) is the best characterized member of the IAP family and is a potent inhibitor of the caspase/apoptosis pathway. It has also been revealed that XIAP has additional biological functions that rely on its direct inhibition of apoptosis. In the present study, stably transfected Caki-1 cells with XIAP-knockdown were generated, and an isobaric tag for relative and absolute quantitation-based proteomics approach was employed to investigate the regulatory mechanism of XIAP in renal cell carcinoma (RCC). The results demonstrate that the sensitivity of the RCC cell line to apoptotic stimulation increased markedly with XIAP-knockdown. A number of differentially expressed proteins were detected between the original Caki-1 cell line and the XIAP-knockdown Caki-1 cell line; 87 at 0 h (prior to etoposide treatment), 178 at 0.5 h and 169 at 3 h, while no differentially expressed proteins were detected (ratio >1.5 or <0.5; P<0.05) at 12 h after etoposide treatment. Through analysis of the differentially expressed proteins, it was revealed that XIAP may participate in the tumor protein p53 pathway, the Wnt signaling pathway, glucose metabolism, endoplasmic reticulum stress, cytoskeletal regulation and DNA repair. These results indicate that XIAP may have a number of biological functions and may provide an insight into the biomedical significance of XIAP overexpression in RCC.

XIAP underlies apoptosis resistance of renal cell carcinoma cells.

X­linked inhibitor of apoptosis (XIAP), a key member of the inhibitors of apoptosis protein family, can inhibit apoptosis by directly binding to the initiator caspase­9, ­3 and ­7, thereby promoting tumor cell survival during tumor progression. In the present study, XIAP basal expression levels were investigated and its contribution to the resistance to apoptosis was evaluated, in the RCC cell lines exposed to apoptosis­inducing drugs. This was investigated by histological methods and western blot analysis. Using RNA interference, elimination of XIAP in Caki­1 cells was also studied, and its contribution to the sensitivity to apoptosis induced through the intrinsic pathway was observed. Differences in XIAP expression were detected between ClearCa­2 and ClearCa­6 cell lines. ClearCa­6 cells with lower expression of XIAP were more sensitive to apoptosis­inducing drugs, compared with ClearCa­2 cells. However, the levels of XIAP expression in both cell lines were stable during apoptosis. Furthermore, a Caki­1 cell line with no XIAP expression was used, and was demonstrated to be more sensitive to the apoptosis induced by the mitochondrial pathway. These results suggested that downregulation of XIAP expression could enhance the sensitivity of RCC cells to apoptosis, and the basal expression of XIAP during apoptosis is stable. This may provide novel insight for targeted gene therapy against XIAP, in the clinic.

[Research on the method of transient spectrum detection based on array CCD].

Based on the characteristic of high speed line scanning for CCD in transient spectrum detection, a method of transient spectrum detection with array CCD is presented. The high speed line scanning with array CCD was realized by changing the mode of charge transfer. In order to explore the feasibility of this method, a fast detection system of single point based on linear CCD was designed and fabricated. Seven different LED pulses were measured when the system worked at fast detection mode of single point and normal mode respectively. The results demonstrate that the method of fast detection of single point based on linear CCD is feasible, and the rate of single point detection reaches up to 20 MHz. Thus, in theory, it was proved that transient spectrum detection with array CCD by changing the mode of charge transfer is also feasible.

[Real-time measurement of detonation transient temperature].

Based on the spectral characteristic of the detonation temperature, the present paper presents a measurement system of transient multi-wavelength pyrometry with the theory of multi-wavelength thermometry. The FPGA was applied as the hardware developing platform and the high-speed linear CCD was utilized. Each module was controlled by FPGA to achieve the process of real-time data acquisition, storage and transmission. Using the multiple regression analysis method, the dynamic spectral waveforms were calculated. The two laser spectral lines, 630 and 532 nm, were used to calibrate the corresponding pixel sequence numbers and the No. 175 and No. 270 were confirmed. In this paper, the halide tungsten light was measured. The results show that the system can sample continuous spectrum signal at several different times; the CCD can stably work with 40 MHz clock and the frame scanning frequency can achieve 73 kHz.

[Study on the spectrum response characteristic based on the wide type bacteriorhodopsin film].

The photochromic retinal protein bacteriorhodopsin (BR) was found in the cell membrane of the Archaean Halobacterium salinarium. The excellent photochromic and photocycle properties of the BR provide the possibility of many applications in the filed of optical information processing. In this paper, the spectrum response characteristic of the wild type bacteriorhodopsin molecule film was studied by using pump-probe method. After the samples was excited by 532 nm YAG laser beam, the absorption spectra were probed by an optical fiber spectrum analysis (OSA). The absorption peaks at the ground state (B state) of the two samples are all at 562 nm wavelength. At 562 nm wavelength, the optical densities (OD) of the samples are about OD (WT1) 562 nm = 2.04 and OD (WT2) 562 nm = 1.37 respectively. The experiment results show that BR(WT) films have absorption that appears to strengthen with the probe time increasing in wavelength 550-650 nm, and this change phenomenon is described by spectra measured at different probe time. Appling the theoretical plot-fit of two exponentials to analyze the process of the absorption change it is found that this change includes two processes-fast process and slow process. Their corresponse time constants of BR(WT1) are about 11 ms and 60 s, and those of BR(WT2) about 24 and 30 s respectively.