Integrin-linked kinase, a promising cancer therapeutic target: biochemical and biological properties

Integrin-linked kinase (ILK) is an ankyrin repeat-containing Ser/Thr kinase that interacts with the cytoplasmic domains of beta(1) and beta(3) integrins. ILK is widely expressed in tissues throughout the body, and, as might be expected, appears to mediate a diversity of functions relating to its role in coupling integrins and growth factor receptors to downstream signaling pathways. Through its downstream targets protein kinase B/Akt and glycogen synthase kinase-3beta, ILK appears to be involved in several oncogenesis-related events, including suppression of apoptosis and promotion of cell survival, as well as cell migration and invasion. Over-expression of ILK in epithelial cells results in anchorage-independent cell growth with increased cell cycle progression. Inoculation of nude mice with ILK over-expressing cells leads to tumor formation. Furthermore, increased ILK expression and activity have been correlated with malignancy in several human tumor types, including breast, prostate, brain, and colon carcinomas. Based on these findings, ILK represents an excellent therapeutic target for the prevention of tumor progression. Here, we provide an overview of the physical and biochemical properties of ILK, and present data describing the impact of small-molecule ILK inhibitors on several ILK-mediated cellular functions.

Integrin-linked kinase, a promising cancer therapeutic target: biochemical and biological properties

Integrin-linked kinase (ILK) is an ankyrin repeat-containing Ser/Thr kinase that interacts with the cytoplasmic domains of beta(1) and beta(3) integrins. ILK is widely expressed in tissues throughout the body, and, as might be expected, appears to mediate a diversity of functions relating to its role in coupling integrins and growth factor receptors to downstream signaling pathways. Through its downstream targets protein kinase B/Akt and glycogen synthase kinase-3beta, ILK appears to be involved in several oncogenesis-related events, including suppression of apoptosis and promotion of cell survival, as well as cell migration and invasion. Over-expression of ILK in epithelial cells results in anchorage-independent cell growth with increased cell cycle progression. Inoculation of nude mice with ILK over-expressing cells leads to tumor formation. Furthermore, increased ILK expression and activity have been correlated with malignancy in several human tumor types, including breast, prostate, brain, and colon carcinomas. Based on these findings, ILK represents an excellent therapeutic target for the prevention of tumor progression. Here, we provide an overview of the physical and biochemical properties of ILK, and present data describing the impact of small-molecule ILK inhibitors on several ILK-mediated cellular functions.

Activity of recombinant dengue 2 virus NS3 protease in the presence of a truncated NS2B co-factor, small peptide substrates, and inhibitors

Recombinant forms of the dengue 2 virus NS3 protease linked to a 40-residue co-factor, corresponding to part of NS2B, have been expressed in Escherichia coli and shown to be active against para-nitroanilide substrates comprising the P6-P1 residues of four substrate cleavage sequences. The enzyme is inactive alone or after the addition of a putative 13-residue co-factor peptide but is active when fused to the 40-residue co-factor, by either a cleavable or a noncleavable glycine linker. The NS4B/NS5 cleavage site was processed most readily, with optimal processing conditions being pH 9, I = 10 mm, 1 mm CHAPS, 20% glycerol. A longer 10-residue peptide corresponding to the NS2B/NS3 cleavage site (P6-P4') was a poorer substrate than the hexapeptide (P6-P1) para-nitroanilide substrate under these conditions, suggesting that the prime side substrate residues did not contribute significantly to protease binding. We also report the first inhibitors of a co-factor-complexed, catalytically active flavivirus NS3 protease. Aprotinin was the only standard serine protease inhibitor to be active, whereas a number of peptide substrate analogues were found to be competitive inhibitors at micromolar concentrations.

Prospective randomized clinical trial of the value of intraperitoneal drainage after pancreatic resection

OBJECTIVE

To test the hypothesis that routine intraperitoneal drainage is not required after pancreatic resection.

SUMMARY BACKGROUND DATA

The use of surgically placed intraperitoneal drains has been considered routine after pancreatic resection. Recent studies have suggested that for other major upper abdominal resections, routine postoperative drainage is not required and may be associated with an increased complication rate.

METHODS

After informed consent, eligible patients with peripancreatic tumors were randomized during surgery either to have no drains placed or to have closed suction drainage placed in a standardized fashion after pancreatic resection. Clinical, pathologic, and surgical details were recorded.

RESULTS

One hundred seventy-nine patients were enrolled in the study, 90 women and 89 men. Mean age was 65.4 years (range 23-87). The pancreas was the tumor site in 142 (79%) patients, with the ampulla (n = 24), duodenum (n = 10), and distal common bile duct (n = 3) accounting for the remainder. A pancreaticoduodenectomy was performed in 139 patients and a distal pancreatectomy in 40 cases. Eighty-eight patients were randomized to have drains placed. Demographic, surgical, and pathologic details were similar between both groups. The overall 30-day death rate was 2% (n = 4). A postoperative complication occurred during the initial admission in 107 patients (59%). There was no significant difference in the number or type of complications between groups. In the drained group, 11 patients (12.5%) developed a pancreatic fistula. Patients with a drain were more likely to develop a significant intraabdominal abscess, collection, or fistula.

CONCLUSION

This randomized prospective clinical trial failed to show a reduction in the number of deaths or complications with the addition of surgical intraperitoneal closed suction drainage after pancreatic resection. The data suggest that the presence of drains failed to reduce either the need for interventional radiologic drainage or surgical exploration for intraabdominal sepsis. Based on these results, closed suction drainage should not be considered mandatory or standard after pancreatic resection.

Gastrointestinal stromal tumors and leiomyosarcoma of the abdomen and retroperitoneum: a clinical comparison

INTRODUCTION

The present study was undertaken to define the clinical differences between leiomyosarcomas (LMS) occurring within the abdomen and retroperitoneum and gastrointestinal stromal tumors (GIST).

METHODS

It was a retrospective, single-institution review of patients treated for intra-abdominal and retroperitoneal GIST and LMS from July 1, 1982 through August 1, 1999.

RESULTS

A total of 561 patients, 239 with GIST and 322 with LMS, were identified. Patients with GIST were older, with a median age of 58 years versus 54 years in the LMS group (P < .01). The majority of patients with GIST were male (58%), whereas 68% of LMS patients (excluding gender-specific sites) were female (P < .01). The 5-year disease-specific survival for GIST and LMS were 28% and 29%, respectively. The presentation status and ability to achieve a complete surgical resection were the main independent predictors of outcome for both GIST and LMS. Local and distant recurrence was common in both. The pattern of distant recurrence differed: 50% of all first-site GIST recurrences involved the liver, whereas 30% of all LMS first-site recurrences involved the lungs.

CONCLUSIONS

Although the two patient populations appear to be distinct, their clinical courses are similar. The pattern of distant spread follows the known patterns of hematogenous dissemination. Complete surgical resection is the cornerstone of treatment for primary GIST and LMS and in selected patients with local and distant recurrence.

Gastrointestinal stromal tumors and leiomyosarcoma of the abdomen and retroperitoneum: a clinical comparison

INTRODUCTION

The present study was undertaken to define the clinical differences between leiomyosarcomas (LMS) occurring within the abdomen and retroperitoneum and gastrointestinal stromal tumors (GIST).

METHODS

It was a retrospective, single-institution review of patients treated for intra-abdominal and retroperitoneal GIST and LMS from July 1, 1982 through August 1, 1999.

RESULTS

A total of 561 patients, 239 with GIST and 322 with LMS, were identified. Patients with GIST were older, with a median age of 58 years versus 54 years in the LMS group (P < .01). The majority of patients with GIST were male (58%), whereas 68% of LMS patients (excluding gender-specific sites) were female (P < .01). The 5-year disease-specific survival for GIST and LMS were 28% and 29%, respectively. The presentation status and ability to achieve a complete surgical resection were the main independent predictors of outcome for both GIST and LMS. Local and distant recurrence was common in both. The pattern of distant recurrence differed: 50% of all first-site GIST recurrences involved the liver, whereas 30% of all LMS first-site recurrences involved the lungs.

CONCLUSIONS

Although the two patient populations appear to be distinct, their clinical courses are similar. The pattern of distant spread follows the known patterns of hematogenous dissemination. Complete surgical resection is the cornerstone of treatment for primary GIST and LMS and in selected patients with local and distant recurrence.

Regulation of protein kinase B/Akt-serine 473 phosphorylation by integrin-linked kinase: critical roles for kinase activity and amino acids arginine 211 and serine 343

Protein kinase B (PKB/Akt) is a regulator of cell survival and apoptosis. To become fully activated, PKB/Akt requires phosphorylation at two sites, threonine 308 and serine 473, in a phosphatidylinositol (PI) 3-kinase-dependent manner. The kinase responsible for phosphorylation of threonine 308 is the PI 3-kinase-dependent kinase-1 (PDK-1), whereas phosphorylation of serine 473 has been suggested to be regulated by PKB/Akt autophosphorylation in a PDK-1-dependent manner. However, the integrin-linked kinase (ILK) has also been shown to regulate phosphorylation of serine 473 in a PI 3-kinase-dependent manner. Whether ILK phosphorylates this site directly or functions as an adapter molecule has been debated. We now show by in-gel kinase assay and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry that biochemically purified ILK can phosphorylate PKB/Akt directly. Co-immunoprecipitation analysis of cell extracts demonstrates that ILK can complex with PKB/Akt as well as PDK-1 and that ILK can disrupt PDK-1/PKB association. The amino acid residue serine 343 of ILK within the activation loop is required for kinase activity as well as for its interaction with PKB/Akt. Mutational analysis of ILK further shows a crucial role for arginine 211 of ILK within the phosphoinositide phospholipid binding domain in the regulation of PKB- serine 473 phosphorylation. A highly selective small molecule inhibitor of ILK activity also inhibits the ability of ILK to phosphorylate PKB/Akt in vitro and in intact cells. These data demonstrate that ILK is an important upstream kinase for the regulation of PKB/Akt.

A novel vascular smooth muscle chymase is upregulated in hypertensive rats

While greater than 80% of angiotensin II (Ang II) formation in the human heart and greater than 60% in arteries appears to result from chymase activity, no cardiovascular cell-expressed chymase has been previously reported. We now describe the cloning of a full-length cDNA encoding a novel chymase from rat vascular smooth muscle cells. The cDNA encompasses 953 nucleotides, encodes 247 amino acids, and exhibits 74% and 80% homology in amino acid sequence to rat mast cell chymase I and II, respectively. Southern blot analysis indicates that the rat vascular chymase is encoded by a separate gene. This chymase was induced in hypertrophied rat pulmonary arteries, with 11-fold and 8-fold higher chymase mRNA levels in aortic and pulmonary artery smooth muscle cells from spontaneously hypertensive than in corresponding tissues from normotensive rats. We assayed the activity of the endogenous enzyme and of a recombinant, epitope-tagged chymase in transfected smooth muscle cells and showed that Ang II production from Ang I can be inhibited with chymostatin, but not EDTA or captopril. Spontaneously hypertensive rats show elevated chymase expression and increased chymostatin-inhibitable angiotensin-converting activity, suggesting a possible role for this novel enzyme in the pathophysiology of hypertension.

Ikirara insertions reveal five new Anopheles gambiae transposable elements in islands of repetitious sequence

Characterization of Anopheles gambiae genomic clones containing Ikirara inverted repeats revealed five novel sequences related to known transposable elements (TEs). One TE is related to the mariner/Tc1 superfamily of class II (DNA-to-DNA) transposons, while four are related to class I (RNA-mediated transposition) elements. Crusoe, the class II element; is most similar to the Caenorhabditis elegans transposon Tc1-like TEs. Vash elements, represented twice in our clones, are related to the Q/T1 family of A. gambiae non-LTR retrotransposable elements. Guildenstern is a member of the RT1 and RT2 non-LTR retrotransposon family. Although RT1 and RT2 elements normally have a highly stereotyped insertion preference for sequences within ribosomal genes, Guildenstern is not located in ribosomal sequence. JuanAg is the first anopheline member of the mosquito non-LTR retrotransposon family of Juan elements that previously had included just the culicine elements JuanA and JuanC. Approximately 753 bp is missing from the central portion of the JuanAg reverse transcriptase gene, where an Ikirara inverted repeat is found in its stead. Ozymandias, the only LTR retrotransposon found in the clones, is most similar to the Drosophila melanogaster 412 element. Single Ikirara inverted repeats were also found adjacent to nontransposable element repetitious sequences. Our analysis suggests that the A. gambiae genome organization could best be described as islands of short-period interspersion repetitious DNA in a sea of long-period interspersion, mostly unique sequence DNA.

Extended hepatic resection: a 6-year retrospective study of risk factors for perioperative mortality

BACKGROUND

Extended hepatic resection (more than four liver segments) is a major operative procedure that is associated with significant risk. The purpose of this study was to assess the impact of perioperative variables on in-hospital mortality after extended hepatectomy.

STUDY DESIGN

Consecutive patients who underwent extended hepatic resection were studied. The prognostic value of 29 perioperative variables was evaluated using in-hospital mortality as the endpoint. For each variable, the odds ratio (95% confidence interval) for in-hospital mortality was calculated. Those variables with a lower confidence limit > 1 were considered important risk factors. The population was stratified into categories of patients having the same number of risk factors, and mortality was estimated for each group. These data were used to develop a risk assessment algorithm.

RESULTS

There were 14 deaths (6%) in 226 patients. Three preoperative variables (cholangitis, creatinine > 1.3 mg/dL, and total bilirubin > 6 mg/dL) and two operative variables (blood loss > 3 L and vena caval resection) appear to be important factors for in-hospital mortality. The mortality associated with the presence of any two of the five factors was 100% (5 of 5), and the mortality associated with the absence of these factors was 3% (6 of 191).

CONCLUSIONS

Perioperative evaluation of patients undergoing extended hepatic resection should include the quantitation of mortality risk factors. The combination of any two factors among preoperative cholangitis, elevated serum creatinine, elevated serum bilirubin, high operative blood loss, and vena cava resection may carry a high mortality risk. These results require prospective validation.

Integrin-linked kinase (ILK): a "hot" therapeutic target

Integrin-mediated cell adhesion is known to regulate gene expression through the activation of transcription factors. We have recently revealed that these activations are mediated through integrin-linked kinase (ILK). ILK is an ankyrin repeat-containing serine-threonine protein kinase that can interact directly with the cytoplasmic domain of the beta1 and beta3 integrin subunits and whose kinase activity is modulated by cell-extracellular matrix interactions. We have shown that ILK overexpression results in the translocation of beta-catenin to the nucleus, which then forms a complex formation with the lymphoid enhancer binding factor 1 (LEF-1) transcription factor, subsequently activating the transcriptional activity of promoters containing LEF-1 response elements. ILK phosphorylates the glycogen synthase kinase-3 (GSK-3), which inhibits GSK-3 activity. We have demonstrated that ILK stimulates activator protein-1 transcriptional activity through GSK-3 and the subsequent regulation of the c-Jun-DNA interaction. ILK also phosphorylates protein kinase B (PKB/Akt) and stimulates its activity. We have shown that ILK is an upstream effector of the phosphatidylinositol 3-kinase-dependent regulation of PKB/Akt. ILK has been shown to phosphorylate PKB/Akt on Ser-473 in vitro and in vivo. Our results clearly indicate that ILK is a key element in the regulation of integrin signaling as well as growth factor and Wnt signaling pathways. PTEN (phosphatase and tensin homolog detected on chromosome 10) is a tumor suppressor gene located on chromosome 10q23 that encodes a protein and phospholipid phosphatase. It is now estimated that inactivation mutants of PTEN exist in 60% of all forms of solid tumors. Loss of expression or mutational inactivation of PTEN leads to the constitutive activation of PKB/Akt via enhanced phosphorylation of Thr-308 and Ser-473. We have demonstrated that the activity of ILK is constitutively elevated in PTEN mutant cells. A small molecule ILK inhibitor suppresses the phosphorylation of PKB at the Ser-473 but not the Thr-308 site in the PTEN mutant cells. These results indicate that inhibition of ILK may be of significant value in solid tumor therapy.