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Double inhibition of XIAP and Bcl-2 axis is beneficial for retrieving sensitivity of renal cell cancer to apoptosis.

Bilim V, Yuuki K, Itoi T, Muto A, Kato T, Nagaoka A, Motoyama T, Tomita Y - Br. J. Cancer (2008)

Bottom Line: Compared to the parental and mock-transfected cells, neither clone was more sensitive to conventional chemotherapeutic agents, but both clones were more susceptible to Fas stimulation (P<0.0001) and to pharmacological Bcl-2 inhibition (P<0.0001), as well as to a combination of the two (P<0.0001).We determined that exposure of Caki1 cells to Smac-N7 peptide (AVPIAQK) resulted in a slight but significant decrease in viability (P=0.0031) and potentiated cisplatin's effect (P=0.0027).Our results suggest that multiple targeting of both Bcl-2 and XIAP or, alternatively, of several IAP family members by the Smac-N7 peptide is a potent way to overcome resistance of RCC to apoptosis-triggering treatment modalities, and might be a new tool for molecular targeted therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Yamagata University School of Medicine, Iida-nishi 2-2-2, Yamagata 990-9585, Japan.

ABSTRACT
Renal cell carcinoma (RCC) is known to be resistant to chemo- and radiotherapy due to a high apoptotic threshold. Smac and XIAP (X-linked inhibitor of apoptosis protein) proteins were detected in all RCC cell lines and tissue samples examined. We modulated the function of XIAP, either through its constitutional downregulation with an shRNA vector or by applying a Smac-mimicking peptide. Among RCC cell lines, Caki1 expresses the highest levels of XIAP. We transfected Caki1 with XIAP-targeting shRNA vector and generated stable clones. XIAP was knocked down by RNA interference in clone no. 14 by 81.6% and in clone no. 19 by 85.3%. Compared to the parental and mock-transfected cells, neither clone was more sensitive to conventional chemotherapeutic agents, but both clones were more susceptible to Fas stimulation (P<0.0001) and to pharmacological Bcl-2 inhibition (P<0.0001), as well as to a combination of the two (P<0.0001). Mature Smac binds to XIAP via the N-terminal residues, disrupting its interaction with caspases and promoting their activity. We determined that exposure of Caki1 cells to Smac-N7 peptide (AVPIAQK) resulted in a slight but significant decrease in viability (P=0.0031) and potentiated cisplatin's effect (P=0.0027). In contrast with point targeting of XIAP by shRNA, Smac-N7 peptide is active against several IAP (inhibitor of apoptosis protein) family members, which can explain its role in sensitising cells to cisplatin. Our results suggest that multiple targeting of both Bcl-2 and XIAP or, alternatively, of several IAP family members by the Smac-N7 peptide is a potent way to overcome resistance of RCC to apoptosis-triggering treatment modalities, and might be a new tool for molecular targeted therapy.

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Immunohistochemical examination of Smac (A, C) and XIAP (B, D) in normal kidney (A, B) and RCC (C, D). In normal kidney, Smac expression was detected in tubular epithelial cells, Bowman capsule cells, and a portion of glomerular cells (A). In tumours, Smac staining was weaker than in normal kidney (C). XIAP expression was restricted to tubular epithelial and several glomerular cells in normal kidney (B).
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fig1: Immunohistochemical examination of Smac (A, C) and XIAP (B, D) in normal kidney (A, B) and RCC (C, D). In normal kidney, Smac expression was detected in tubular epithelial cells, Bowman capsule cells, and a portion of glomerular cells (A). In tumours, Smac staining was weaker than in normal kidney (C). XIAP expression was restricted to tubular epithelial and several glomerular cells in normal kidney (B).

Mentions: By IHC, XIAP expression was found to be restricted to tubular epithelial and several glomerular cells, and Smac expression was detected in tubular epithelial cells, Bowman capsule cells, a portion of glomerular cells, and fibroblasts in normal kidney (Figure 1). In tumourous tissues, Smac was found in all tumours, with staining scores ranging from 200 to 300 and staining intensity weaker than in normal kidneys. Smac expression did not vary between different tumour stages and grades. XIAP expression levels increased from pT1 (164.423±108.170) to pT2 (195.000±83.367) and pT3 (266.667±57.735), as well as from grade 1 (75.000±98.742) to grade 2 (201.250±93.695) (P<0.05). However, in grade 3, the staining score decreased slightly (173.333±110.151). The chromophobe histological subtype presented with a higher staining score (275.000±35.355) than the clear cell type (171.724±107.614) or papillary type (173.333±75.056), but the difference was not significant.


Double inhibition of XIAP and Bcl-2 axis is beneficial for retrieving sensitivity of renal cell cancer to apoptosis.

Bilim V, Yuuki K, Itoi T, Muto A, Kato T, Nagaoka A, Motoyama T, Tomita Y - Br. J. Cancer (2008)

Immunohistochemical examination of Smac (A, C) and XIAP (B, D) in normal kidney (A, B) and RCC (C, D). In normal kidney, Smac expression was detected in tubular epithelial cells, Bowman capsule cells, and a portion of glomerular cells (A). In tumours, Smac staining was weaker than in normal kidney (C). XIAP expression was restricted to tubular epithelial and several glomerular cells in normal kidney (B).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2266840&req=5

fig1: Immunohistochemical examination of Smac (A, C) and XIAP (B, D) in normal kidney (A, B) and RCC (C, D). In normal kidney, Smac expression was detected in tubular epithelial cells, Bowman capsule cells, and a portion of glomerular cells (A). In tumours, Smac staining was weaker than in normal kidney (C). XIAP expression was restricted to tubular epithelial and several glomerular cells in normal kidney (B).
Mentions: By IHC, XIAP expression was found to be restricted to tubular epithelial and several glomerular cells, and Smac expression was detected in tubular epithelial cells, Bowman capsule cells, a portion of glomerular cells, and fibroblasts in normal kidney (Figure 1). In tumourous tissues, Smac was found in all tumours, with staining scores ranging from 200 to 300 and staining intensity weaker than in normal kidneys. Smac expression did not vary between different tumour stages and grades. XIAP expression levels increased from pT1 (164.423±108.170) to pT2 (195.000±83.367) and pT3 (266.667±57.735), as well as from grade 1 (75.000±98.742) to grade 2 (201.250±93.695) (P<0.05). However, in grade 3, the staining score decreased slightly (173.333±110.151). The chromophobe histological subtype presented with a higher staining score (275.000±35.355) than the clear cell type (171.724±107.614) or papillary type (173.333±75.056), but the difference was not significant.

Bottom Line: Compared to the parental and mock-transfected cells, neither clone was more sensitive to conventional chemotherapeutic agents, but both clones were more susceptible to Fas stimulation (P<0.0001) and to pharmacological Bcl-2 inhibition (P<0.0001), as well as to a combination of the two (P<0.0001).We determined that exposure of Caki1 cells to Smac-N7 peptide (AVPIAQK) resulted in a slight but significant decrease in viability (P=0.0031) and potentiated cisplatin's effect (P=0.0027).Our results suggest that multiple targeting of both Bcl-2 and XIAP or, alternatively, of several IAP family members by the Smac-N7 peptide is a potent way to overcome resistance of RCC to apoptosis-triggering treatment modalities, and might be a new tool for molecular targeted therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Yamagata University School of Medicine, Iida-nishi 2-2-2, Yamagata 990-9585, Japan.

ABSTRACT
Renal cell carcinoma (RCC) is known to be resistant to chemo- and radiotherapy due to a high apoptotic threshold. Smac and XIAP (X-linked inhibitor of apoptosis protein) proteins were detected in all RCC cell lines and tissue samples examined. We modulated the function of XIAP, either through its constitutional downregulation with an shRNA vector or by applying a Smac-mimicking peptide. Among RCC cell lines, Caki1 expresses the highest levels of XIAP. We transfected Caki1 with XIAP-targeting shRNA vector and generated stable clones. XIAP was knocked down by RNA interference in clone no. 14 by 81.6% and in clone no. 19 by 85.3%. Compared to the parental and mock-transfected cells, neither clone was more sensitive to conventional chemotherapeutic agents, but both clones were more susceptible to Fas stimulation (P<0.0001) and to pharmacological Bcl-2 inhibition (P<0.0001), as well as to a combination of the two (P<0.0001). Mature Smac binds to XIAP via the N-terminal residues, disrupting its interaction with caspases and promoting their activity. We determined that exposure of Caki1 cells to Smac-N7 peptide (AVPIAQK) resulted in a slight but significant decrease in viability (P=0.0031) and potentiated cisplatin's effect (P=0.0027). In contrast with point targeting of XIAP by shRNA, Smac-N7 peptide is active against several IAP (inhibitor of apoptosis protein) family members, which can explain its role in sensitising cells to cisplatin. Our results suggest that multiple targeting of both Bcl-2 and XIAP or, alternatively, of several IAP family members by the Smac-N7 peptide is a potent way to overcome resistance of RCC to apoptosis-triggering treatment modalities, and might be a new tool for molecular targeted therapy.

Show MeSH
Related in: MedlinePlus