Bcl-x_L and Myeloid cell leukaemia-1 contribute to apoptosis resistance of colorectal cancer cells

AIM: To explore the role of Bcl-xL and Myeloid cell leukaemia (Mcl)-1 for the apoptosis resistance of colorectal carcinoma (CRC) cells towards current treat-ment modalities. METHODS: Bcl-xL and Mcl-1 mRNA and protein ex-pression were analyzed in CRC cell lines as well as human CRC tissue by Western blot,quantitative PCRand immunohistochemistry. Bcl-xL and Mcl-1 protein expression was knocked down or increased in CRC cell lines by applying specific siRNAs or expression plas-mids,respectively. After modulation of protein expres-sion,CRC cells were treated with chemotherapeutic agents,an antagonistic epidermal growth factor recep-tor (EGFR1) antibody,an EGFR1 tyrosine kinase inhibi-tor,or with the death receptor ligand TRAIL. Apoptosis induction and cell viability were analyzed. RESULTS: Here we show that in human CRC tis-sue and various CRC cell lines both Bcl-xL and Mcl-1 are expressed. Bcl-xL expression was higher in CRC tissue than in surrounding non-malignant tissue,both on protein and mRNA level. Mcl-1 mRNA expression was significantly lower in ma-lignant tissues. However,protein expression was slightly higher. Viability rates of CRC cells were significantly decreased after knock down of Bcl-xL expression,and,to a lower extent,after knock down of Mcl-1 expression. Furthermore,cells with reduced Bcl-xL or Mcl-1 expression was more sensitive towards oxaliplatin-and irinotecan-induced apoptosis,and in the case of Bcl-xL also towards 5-FU-induced apoptosis. On the other hand,upregulation of Bcl-xL by transfec-tion of an expression plasmid decreased chemothera-peutic drug-induced apoptosis. EGF treatment clearly induced Bcl-xL and Mcl-1 expression in CRC cells. Apop-tosis induction upon EGFR1 blockage by cetuximab or PD168393 was increased by inhibiting Mcl-1 and Bcl-xL expression. More strikingly,CD95-and TRAIL-induced apoptosis was increased by Bcl-xL knock down. CONCLUSION: Our data suggest that Bcl-xL and,to a lower extent,Mcl-1,are important anti-apoptotic factors in CRC. Specific downregulation of Bcl-xL is a promising approach to sensitize CRC cells towards chemotherapy and targeted therapy.

Coexpression of receptor-tyrosine-kinases in gastric adenocarcinoma-a rationale for a molecular targeting strategy?

AIM: To define the (co-)expression pattern of target receptor-tyrosine-kinases (RTK) in human gastric adenocarcinoma. METHODS: The (co-)expression pattern of VEGFR1-3,PDGFRα/b and EGFR1 was analyzed by RT-PCR in 51 human gastric adenocarcinomas. In addition,IHC staining was applied for confirmation of expression and analysis of RTK localisation. RESULTS: The majority of samples revealed a VEGFR1 (98%),VEGFR2 (80%),VEGFR3 (67%),PDGFRα (82%) and PDGFRβ(82%) expression,whereas only 62% exhibited an EGFR1 expression. 78% of cancers expressed at least four out of six RTKs. While VEGFR1-3 and PDGFRα revealed a predominantly cytoplasmatic staining in tumor cells,accompanied by an additional nuclear staining for VEGFR3 ,EGFR1 was almost exclusively detected on the membrane of tumor cells. PDGFRβ was restricted to stromal pericytes,which also depicted a PDGFRα expression.receptor-tyrosine-kinases coexpression in gastric adenocarcinoma and might therefore encourage an application of multiple-target RTK-inhibitors within a combination therapy.

SIBLINGs and SPARC families: Their emerging roles in pancreatic cancer

Pancreatic cancer has a considerably poor prognosis with a 5-year survival probability of less than 5%when all stages are combined.Pancreatic cancer is characterized by its dense stroma,which is involved in the critical interplay with the tumor cells throughout tumor progression and furthermore,creates a barrier restricting efficient penetration of therapeutics.Alterations in a large number of genes are reflected by a limited number of signaling pathways,which are potential targets.Understanding more about the molecular basis of this devastating cancer type regarding tumor microenvironment,distinct subpopulations of cells,epithelial-to-mesenchymal transition and inflammation will lead to the development of various targeted therapies for controlling tumor growth and metastasis.In this complex scenario of pancreatic cancer,especially members of the"small integrin binding ligand N-linked glycoproteins"(SIBLINGs)and"secreted protein acidic and rich in cysteine"(SPARC)families have emerged due to their prominent roles in properties including proliferation,dif-ferentiation,apoptosis,adhesion,migration,angiogenesis,wound repair and regulation of extracellular matrix remodeling.SIBLINGs consist of five members,which include osteopontin(OPN),bone sialoprotein,dentin matrix protein 1,dentin sialophosphoprotein and matrix extracellular phosphoglycoprotein.The SPARC family of modular extracellular proteins is comprised of SPARC/osteonectin(ON)and SPARC-like 1(hevin);secreted modular calcium binding proteins;testicans and follistatin-like protein.In this review,we especially focus on OPN and ON,elaborating on their special and growing importance in pancreatic cancer diagnosis and prognosis.