The role of faecal diversion in low rectal cancer: a review of 1791 patients having rectal resection with anastomosis for cancer, with and without a proximal stoma.

AIM: The morbidity of anastomotic dehiscence may be mitigated by a defunctioning stoma, but it is unclear if it is required for most low rectal anastomoses. Preoperative risk factors leading to anastomotic complications and the indications for faecal diversion have yet to be clearly defined. METHOD: Using the American College of Surgeons-National Surgical Quality Improvement Project (ACS-NSQIP) participant-use file, patients were identified who underwent low anterior resection with anastomosis for cancer at the 211 participating hospitals in 2005-08. RESULTS: A total of 1791 patients underwent low anterior resection. Patients were subdivided into two groups based on the level of the anastomosis. Of these 1266 patients had a low pelvic anastomosis (LPA) and 525 a coloanal anastomosis (CAA). In the LPA group, 606 patients had a stoma and 660 had no stoma. There were no differences in wound complications, sepsis or septic shock. Patients who had a stoma were more likely to have postoperative acute renal failure (1.7 vs 0.5%, P = 0.0485, OR 3.674). In the CAA group, 352 had a stoma and 173 had no stoma. In patients without faecal diversion, there was a significantly greater incidence of sepsis (8.7 vs 3.7%, P = 0.022, OR 2.47), septic shock (3.5 vs 0.57%, P = 0.018, OR 6.29) and need for reoperation (11 vs 1.7%, P = 0.0001, OR 7.11). Hospital length of stay was significantly longer with CAA and no stoma. On multivariate analysis, not having a stoma with a CAA was a risk factor for serious postoperative morbidity. CONCLUSION: While a defunctioning stoma with a coloanal anastomosis seems to protect from postoperative sepsis, septic shock and need for reoperation, it is likely that it is overused in rectal cancer surgery.

Arginine stimulates intestinal cell migration through a focal adhesion kinase dependent mechanism.

BACKGROUND: L-Arginine is a nutritional supplement that may be useful for promoting intestinal repair. Arginine is metabolised by the oxidative deiminase pathway to form nitric oxide (NO) and by the arginase pathway to yield ornithine and polyamines. AIMS: To determine if arginine stimulates restitution via activation of NO synthesis and/or polyamine synthesis. METHODS: We determined the effects of arginine on cultured intestinal cell migration, NO production, polyamine levels, and activation of focal adhesion kinase, a key mediator of cell migration. RESULTS: Arginine increased the rate of cell migration in a dose dependent biphasic manner, and was additive with bovine serum concentrate (BSC). Arginine and an NO donor activated focal adhesion kinase (a tyrosine kinase which localises to cell matrix contacts and mediates beta1 integrin signalling) after wounding. Arginine stimulated cell migration was dependent on focal adhesion kinase (FAK) signalling, as demonstrated using adenovirus mediated transfection with a kinase negative mutant of FAK. Arginine stimulated migration was dependent on NO production and was blocked by NO synthase inhibitors. Arginine dependent migration required synthesis of polyamines but elevating extracellular arginine concentration above 0.4 mM did not enhance cellular polyamine levels. CONCLUSIONS: These results showed that L-arginine stimulates cell migration through NO and FAK dependent pathways and that combination therapy with arginine and BSC may enhance intestinal restitution via separate and convergent pathways.

Overexpression of the focal adhesion kinase (p125FAK) in the vascular smooth muscle cells of intimal hyperplasia.

PURPOSE: The migration and proliferation of vascular smooth muscle cells (VSMCs) are important events in the development of intimal hyperplasia (IH). The focal adhesion kinase (FAK) gene encodes a protein tyrosine kinase (p125FAK) involved in signal transduction pathways used in cell adhesion, motility, and proliferation. Because alterations in these cellular processes are thought to occur in VSMCs during IH, we studied FAK expression in healthy arteries and veins in comparison with that in pathologic vessels containing IH. METHODS: To determine p125FAK expression at the cellular level, we developed a monoclonal antibody that specifically detected FAK in formalin-fixed, paraffin-embedded tissue sections (5 microm) and analyzed the levels of FAK expression in human arteries and veins. Specificity of monoclonal antibody 4.47 was demonstrated by means of immunofluorescence microscopy showing FAK-specific staining at focal adhesions of healthy human vascular smooth muscle cells (AoSMCs). By using immunohistochemistry techniques, we analyzed the expression of p125FAK in 25 adult human vascular tissue samples from individual patients, which contained a histologically confirmed healthy artery, vein, or IH. RESULTS: FAK expression in healthy and pathologic human vascular tissue was localized predominantly within VSMC cytoplasm. In healthy human artery and vein, borderline FAK expression was detected in the media of seven of 17 vessels and undetectable in the remainder of specimens. However, in vessels containing IH, FAK was overexpressed in the pathologic VSMC populations at moderate-to-strong levels in eight of eight specimens. The levels of FAK expression were directly correlated with structures containing IH, and the results of FAK staining intensity and the percentage of positive cells in these samples were significantly increased compared with normal vascular tissue levels (P <.05, Student t test). CONCLUSION: These results provide the first evidence that FAK is overexpressed in VSMCs involved in IH and suggest that FAK upregulation may be part of a mechanism for migration and proliferation of VSMCs during this process. Furthermore, the dramatic upregulation of FAK in IH and the relative lack of expression in healthy vessels suggest that FAK may be a rational target for controlling IH.

The focal adhesion kinase suppresses transformation-associated, anchorage-independent apoptosis in human breast cancer cells. Involvement of death receptor-related signaling pathways.

The focal adhesion kinase (FAK) is a mediator of cell-extracellular matrix signaling events and is overexpressed in tumor cells. In order to rapidly down-regulate FAK function in normal and transformed mammary cells, we have used adenoviral gene transduction of the carboxyl-terminal domain of FAK (FAK-CD). Transduction of adenovirus containing FAK-CD in breast cancer cells caused loss of adhesion, degradation of p125(FAK), and induced apoptosis. Furthermore, breast tumor cells that were viable without matrix attachment also underwent apoptosis upon interruption of FAK function, demonstrating that FAK is a survival signal in breast tumor cells even in the absence of matrix signaling. In addition, both anchorage-dependent and anchorage-independent apoptotic signaling required Fas-associated death domain and caspase-8, suggesting that a death receptor-mediated apoptotic pathway is involved. Finally, FAK-CD had no effect on adhesion or viability in normal mammary cells, despite the loss of tyrosine phosphorylation of p125(FAK). These results indicate that FAK-mediated signaling is required for both cell adhesion and anchorage-independent survival and the disruption of FAK function involves the Fas-associated death domain and caspase-8 apoptotic pathway.

Immunohistochemical analyses of focal adhesion kinase expression in benign and malignant human breast and colon tissues: correlation with preinvasive and invasive phenotypes.

The focal adhesion kinase (FAK) is a protein tyrosine kinase linked to signaling events between cells and the extracellular matrix. Studies at the Western blot level have demonstrated up-regulation of FAK expression in invasive breast and colon cancers. To assess p125FAK expression at the cellular level, we developed monoclonal antibodies that specifically detected FAK in formalin-fixed, paraffin-embedded tissue sections and analyzed the levels of FAK expression in human breast and colon tissues. Monoclonal antibody 4.47 demonstrated FAK-specific focal adhesion staining by immunofluorescence assays on BT-474 breast cancer cells and detected a Mr 125,000 protein by both Western blotting and immunoprecipitation analyses. Using immunohistochemical techniques, the expression of p125FAK was analyzed in 36 normal and 43 preinvasive or invasive human breast and colon tissues from individual patients. FAK was weakly expressed in most benign breast epithelium but was up-regulated at moderate or strong levels in 14 of 18 invasive breast carcinomas. In seven samples of ductal carcinoma-in situ, FAK was overexpressed. Borderline-to-weak expression of FAK was detected in the normal colonic epithelium. In the invasive colon cancers, FAK was overexpressed at moderate or strong levels in 13 of 15 tumors. Furthermore, FAK expression was up-regulated in areas of dysplastic, premalignant colon epithelium. These results provide the first evidence at the cellular level that FAK expression is variably overexpressed in breast and colon cancer and suggest that up-regulation occurs at an early stage of tumorigenesis.

The National Cancer Data Base Report on treatment patterns for hepatocellular carcinomas: improved survival of surgically resected patients, 1985-1996.

BACKGROUND: The Commission on Cancer data from the National Cancer Data Base (NCDB) has previously reported data evaluating time trends in various cancers, including such elements as stage of disease at diagnosis, treatment, and survival for multiple tumor sites. In this report, data collected from 1985, 1986, 1990, 1991, 1995, and 1996 for primary hepatocellular carcinoma (HCC) tumors are presented. METHODS: The data presented in this review were collected from hospital cancer registries from across the U.S. Eight calls for data have yielded a total 6.9 million cases for the years 1985-1996, including 1158 HCC cases in 1985-1986, 3319 cases in 1990-1991, and 5683 cases in 1994-1995 from hospital cancer registries across the U. S. These data represent approximately 4.3%, 11.2%, and 14.8% of the estimated cases of carcinomas of the liver and biliary tract diagnosed in the U.S. in each of the three respective time periods. RESULTS: The outcome for patients diagnosed with HCC remains poor, with only 10% of patients with American Joint Committee on Cancer Stage I disease surviving 5 years. Approximately 50% of patients received no therapy for their HCC, even those with early stage disease. Over these three time periods, the use of chemotherapy appears to have decreased. Among patients diagnosed with Stage II and III disease a difference in survival was noted between those treated with surgery only and those treated with chemotherapy only. Women appear to have a limited survival advantage over men. CONCLUSIONS: In spite of an overall poor prognosis, subsets of patients with HCC appear to benefit from surgical resection/ablation of their tumor. The decreasing use of chemotherapy and the early reports of newer ablative techniques (e.g., cryotherapy) suggest that other treatment modalities are emerging. These NCDB data provide a baseline for HCC treatment from which prospective studies are being developed to assess the newer treatments as well as the underlying causes.

Liver metastases: comparison of current MR techniques and spiral CT during arterial portography for detection in 20 surgically staged cases.

PURPOSE: To compare spiral computed tomography during arterial portography (CTAP) with current magnetic resonance (MR) imaging, including hepatic arterial-dominant phase, gadolinium-enhanced, spoiled gradient-echo imaging, for the prospective detection of liver metastases in 20 patients who subsequently underwent surgery to confirm findings. MATERIALS AND METHODS: Twenty patients underwent spiral CTAP and MR imaging within 1 week. Spiral CTAP and MR images were interpreted separately in blinded fashion. All patients subsequently had intraoperative confirmation. Sensitivity, specificity, and positive and negative predictive values were determined for lesion detection and segmental distribution. RESULTS: CTAP and MR images demonstrated, respectively, 54 and 60 true-positive lesions, six and one false-positive lesions, 15 and 22 true-negative (i.e., benign) lesions, and eight and two false-negative lesions. CTAP and MR images demonstrated, respectively, 57 and 62 true-positive segmental involvements, six and one false-positive segmental involvements, 89 and 95 true-negative segmental involvements, and eight and two false-negative segmental involvements. No significant difference in lesion detection was observed. CONCLUSION: Spiral CTAP and MR imaging were approximately equivalent for lesion detection in patients who were evaluated preoperatively for resection of liver metastases. The lower cost and fewer problems with artifacts may suggest that MR imaging is the preferred modality for preoperative assessment of patients for surgical treatment of liver metastases.

Overexpression of focal adhesion kinase, a protein tyrosine kinase, in ovarian carcinoma.

BACKGROUND: Focal adhesion kinase (FAK) is a tyrosine kinase that is important to such key functions such as cell adhesion, motility, and invasion. A MEDLINE search of the years 1980-1998 found no previous reports of FAK expression in human ovarian carcinoma. The authors performed experiments to determine whether FAK expression is elevated in this disease. METHODS: Ten normal human ovarian tissue samples and 26 cancer samples from patients with Stage I-IV ovarian carcinoma were obtained. Two ovarian carcinoma cell lines were also analyzed. FAK expression was determined by Western blot analysis with the V39 anti-human FAK polyclonal antibody. The level of FAK protein expression was determined using densitometric scanning of the 125 kD band on autoradiographs of Western immunoblots. RESULTS: Serous cancers expressed fourfold-increased values of FAK relative to normal ovarian tissue (P < 0.0001), and nonserous adenocarcinomas expressed threefold- to fourfold-increased values of FAK (P < 0. 0006). Ovarian carcinoma cell lines also expressed increased values of FAK. With a cutoff of 40, an elevated FAK level was associated with a sensitivity of 93% and specificity of 100%. There was no significant difference in FAK expression with regard to grade or stage of tumor. CONCLUSIONS: FAK is significantly overexpressed in ovarian carcinoma, implying that FAK may play an important role in ovarian carcinogenesis. FAK expression may be useful as a screening tool to identify newly developed disease or as a tumor marker in confirmed cases of epithelial ovarian carcinoma. FAK may also serve as a potential target for therapeutic disruption of ovarian carcinoma progression.

Interactions between two cytoskeleton-associated tyrosine kinases: calcium-dependent tyrosine kinase and focal adhesion tyrosine kinase.

The calcium-dependent tyrosine kinase (CADTK), also known as Pyk2/RAFTK/CAKbeta/FAK2, is a cytoskeleton-associated tyrosine kinase. We compared CADTK regulation with that of the highly homologous focal adhesion tyrosine kinase (FAK). First, we generated site-specific CADTK mutants. Mutation of Tyr402 eliminated autophosphorylation and significantly decreased kinase activity. Mutation of Tyr881, a putative Src kinase phosphorylation site predicted to bind Grb2, had little effect on CADTK regulation. Src family tyrosine kinases resulted in CADTK tyrosine phosphorylation even when co-expressed with the Tyr402/Tyr881 double mutant, suggesting that Src/Fyn etc. phosphorylate additional tyrosine residues. Interestingly, CADTK tyrosine-phosphorylated FAK when both were transiently expressed, but FAK did not phosphorylate CADTK. Biochemical experiments confirmed direct CADTK phosphorylation of FAK. This phosphorylation utilized tyrosine residues other than Tyr397, Tyr925, or Tyr576/Tyr577, suggesting that new SH2-binding sites might be created by CADTK-dependent FAK phosphorylation. Last, expression of the CADTK carboxyl terminus (CRNK) abolished CADTK but not FAK autophosphorylation. In contrast, FAK carboxyl terminus overexpression inhibited both FAK and CADTK autophosphorylation, suggesting that a FAK-dependent cytoskeletal function may be necessary for CADTK activation. Thus, CADTK and FAK, which both bind to some, but not necessarily the same, cytoskeletal elements, may be involved in coordinate regulation of cytoskeletal structure and signaling.

The COOH-terminal domain of the focal adhesion kinase induces loss of adhesion and cell death in human tumor cells.

Focal adhesion kinase (FAK) is a tyrosine kinase that is linked to signaling pathways between cells and their extracellular matrix. An alternate transcript of the COOH-terminal region of the FAK gene, called FAK-related nonkinase, has been shown to act as an inhibitor of FAK in chicken embryo fibroblasts. We have designed an analogous segment of human FAK, FAK COOH-terminal domain (FAK-CD), and transfected this construct into human tumor cells. Expression of FAK-CD inhibited cell growth in BT474 human breast cancer cells and C8161 human melanoma cells. To characterize the nature of growth inhibition, we developed an inducible system of FAK-CD expression and demonstrated that the induced FAK-CD protein localized to focal adhesions, causing cellular rounding, an irreversible loss of adhesion, and subsequent cell death. In addition, expression of FAK-CD reduced tyrosine phosphorylation of FAK, suggesting that FAK-CD may be a potent inhibitor of FAK in human tumor cells.

Malignant hepatic tumors: changes on MRI after hepatic arterial chemoembolization--preliminary findings.

This study describes the MR appearances of malignant hypervascular liver lesions pre- and post-hepatic-arterial chemoembolization, with correlation to serial imaging and clinical responses. Eight patients with malignant hypervascular liver lesions underwent pretreatment and posttreatment MR examination on a 1.5-T MR imager. MR sequences included T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo or turbo spin echo, and dynamic gadolinium-enhanced SGE images. All patients underwent pretreatment, initial posttreatment, and subsequent posttreatment MR studies. The histology of primary tumors included various types of hepatocellular carcinoma (HCC) (four patients: fibrolamellar HCC [one patient], HCC [two patients], mixed HCC/cholangiocarcinoma [one patient]) and liver metastases (four patients: untyped islet cell tumor [two patients], gastrinoma [one patient], carcinoid [one patient]). Response to chemoembolization was determined by three assessments: MR response, serial imaging response, and clinical response. The appearance of MR response to chemoembolization was determined based on the correlation with clinical and serial imaging response. The MR response of lesions that showed good clinical response included: increase in signal intensity on T1-weighted images (three patients), decrease in signal intensity on T2-weighted images (three patients), and negligible or minimal enhancement on immediate postgadolinium images (four patients) after chemoembolization. The most marked change in lesion appearance was observed in lesions < or = 1 cm, which had intense homogeneous enhancement on pretreatment MR studies and negligible enhancement on initial posttreatment MR examinations. MR response of lesions that showed moderate clinical response demonstrated a variety of lesion appearances from substantial change to minimal change. MR response of lesions that showed poor clinical response demonstrated no change in lesion appearances compared with the pretreatment MR study. Our results demonstrated change in appearance of liver lesions between pre- and post-hepatic-arterial chemoembolization MR studies. MR response correlated with response determined by serial imaging studies and clinical findings.

Liver lesion detection, characterization, and effect on patient management: comparison of single-phase spiral CT and current MR techniques.

This study compares liver lesion detection, characterization, and effect on patient management between single-phase spiral CT and MRI using spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo, and serial post gadolinium SGE. All patients with suspected liver lesions who underwent spiral CT and MRI within a 1-month period between January 1993 and September 1996 were included in the study. Spiral CT and MRI were interpreted prospectively in a blinded fashion by separate individual experienced investigators, and lesion detection and characterization were determined. Confirmation was obtained by surgery (6 patients), biopsy (18 patients), imaging follow-up (36 patients), or combined reading of all imaging studies and clinical follow-up (29 patients). Effect on patient management was determined by combined chart review and interview of the patients' physicians and by retrospective clinical assessment performed by a surgical oncologist and medical oncologist separately. Eighty-nine patients were included in the study. Regarding true positive lesion detection, 295 and 519 lesions were detected on spiral CT and MR images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were detected on MR than on spiral CT in 44 of 89 patients (49.4%), and 11 of these 44 patients had lesions shown on MRI in whom no lesions were apparent on CT images. No patients had true positive lesions shown on spiral CT that were not shown on MRI. Regarding lesion characterization, 129 and 466 lesions were characterized on spiral CT and MRI images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were characterized on MR than CT images in 67 patients (75.3%). Regarding effect on patient management, chart review with physician interview demonstrated that findings on MRI provided information that altered patient management as compared with findings on spiral CT in 57 patients. Retrospective clinical evaluation by the surgical and medical oncologist showed that MRI was considered to have a greater effect on patient management than spiral CT in 58 and 55 patients, respectively. Comparing current MRI technique to single-phase spiral CT, MRI detected more lesions in 49.4% and characterized more lesions in 75.3% of patients investigated for focal liver disease. MRI had a greater effect on patient management in each of the three methods than single-phase spiral CT in more than 61% of patients.

Attenuation of the expression of the focal adhesion kinase induces apoptosis in tumor cells.

The focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase implicated in integrin-mediated signal transduction pathways, oncogenic transformation by v-src, and the invasion of human tumors. The overexpression of p125FAK in a variety of human tumors and tumor cell lines in comparison to their nontransformed counterparts suggested that attenuation of p125FAK expression might have an effect on tumor cell proliferation. In this study, we have treated tumor cell lines that expressed high levels of p125FAK with different antisense oligonucleotides to FAK, and have specifically attenuated p125FAK expression. The cells treated with antisense oligonucleotides not only lost their attachment, but also underwent apoptosis. Extensive control oligonucleotide experiments suggested that this attenuation was highly FAK specific. Furthermore, normal human fibroblasts, which did not express high levels of p125FAK, did not lose their attachment or become apoptotic with FAK antisense treatment. These results suggested that FAK is involved in adhesion-mediated growth in tumor cells and that FAK may be a rational gene-directed target for disrupting tumor cell growth.

Malignant liver lesions: comparison of spiral CT arterial portography and MR imaging for diagnostic accuracy, cost, and effect on patient management.

We compared two imaging techniques, spiral CT arterial portography (CTAP) and MR imaging, for diagnostic accuracy, procedural cost, and effect on management of 26 patients referred for hepatic surgery for suspected limited malignant liver disease. CTAP and MR imaging were done within a 1-week period (19 within 24 hours); the results of the studies were interpreted prospectively by separate reviewers. Surgical data were evaluated in conjunction with imaging data in 10 patients. Lesion detection and segmental involvement were determined and sensitivity and specificity were calculated. Procedural cost was determined from hospital billing codes. Effect on patient management was determined by the referring oncologic surgeon. CTAP and MR imaging showed 185 and 176 true-positive malignant lesions, 15 and zero false-positive malignant lesions, zero and 18 true-negative malignant lesions, and 13 and 22 false-negative malignant lesions, respectively. CTAP and MR imaging showed 107 and 105 true-positive segments, 11 and zero false-positive segments, 80 and 91 true-negative segments, and four and six false-negative segments, respectively. There was a significant difference in specificity of segmental involvement between MR imaging (1.0 +/- 0) compared with CTAP (0.88 +/- 0.05), P = .03. Total procedural cost was $3,499 for CTAP and $1,224 for MR imaging. CTAP findings did not change patient management over MR imaging findings in any patient, whereas MR imaging findings resulted in a change in patient management over CTAP findings in seven patients (P = .015). The results of our study suggest that MR imaging has higher diagnostic accuracy and greater effect on patient management than CTAP does and is 64% less expensive.

Focal adhesion kinase as a marker of invasive potential in differentiated human thyroid cancer.

BACKGROUND: The FAK gene encodes a 125-kDa tyrosine kinase (p125FAK) involved in signal transduction pathways used in cell adhesion, motility, and anchorage-independent growth. Because thyroid carcinomas have a wide variability in their propensity for invasion and metastasis, we studied the expression of FAK in a variety of thyroid tissues. METHODS: We synthesized a recombinant N-terminal fragment of the human FAK protein and developed a specific polyclonal antisera. Using Western blot analysis, we assessed the levels of p125FAK expression in 30 human thyroid tissue samples from 27 patients that included paired normal and malignant specimens. Levels of FAK protein in individual tumors were quantitated by densitometric scanning of the immunoblots, and the results were correlated with tumor histology and biologic behavior. RESULTS: The levels of FAK expression were directly correlated with thyroid carcinomas demonstrating the most aggressive phenotypes. The highest levels of p125FAK were seen in follicular carcinomas and tumors associated with distant metastatic foci. In contrast, neoplastic thyroid tissues with limited invasive potential, such as papillary carcinomas, follicular adenomas, and other nonmalignant thyroid lesions, showed minimal p125FAX expression. CONCLUSIONS: Overexpression of FAK may be part of a mechanism for invasion and metastasis of thyroid cancer. Furthermore, the levels of p125FAK may serve as a marker of biologic behavior in this disease.

Correlation of perfusion abnormalities on CTAP and immediate postintravenous gadolinium-enhanced gradient echo MRI.

BACKGROUND: The purpose of this study was to evaluate patients with wedge-shaped perfusion defects seen on spiral CT arterial portography for the presence of transient increased wedge-shaped enhancement on dynamic gadolinium-enhanced gradient echo MR images. METHODS: Nineteen patients underwent CTAP and MRI within a 2-week interval. All patients with wedge-shaped perfusion defects on CT arterial portography were evaluated in a separate review session for the presence of transient increased segmental hepatic enhancement on dynamic gadolinium-enhanced spoiled gradient echo (SGE) MR images. RESULTS: Eight patients were identified to have subsegmental, segmental, or lobar wedge-shaped perfusion defects by CT arterial portography. In 8/8 patients, there was transient wedge-shaped increased hepatic enhancement on MR images which corresponded to the perfusion defects identified on CT arterial portography. Transient increased enhancement on MR images was observed on immediate postgadolinium images as high-signal intensity of the involved subsegment, segment, or lobe. This relatively high-signal area faded to near isointensity in all cases on images obtained at 45 s. CONCLUSION: Wedge-shaped perfusion defects demonstrated by CT arterial portography corresponded to wedge-shaped increased hepatic enhancement following gadolinium administration on SGE MR images.

Altered patterns of retinoblastoma gene product expression in adult soft-tissue sarcomas.

Altered expression of the retinoblastoma (RB) tumour-suppressor gene product (pRB) has been detected in sporadic bone and soft-tissue sarcomas. Earlier studies, analysing small cohorts of sarcoma patients, have suggested that these alterations are more commonly associated with high-grade tumours, metastatic lesions and poorer survival. This study was designed to re-examine the prevalence and clinical significance of altered pRB expression in a large and selected group of soft-tissue sarcomas from 174 adult patients. Representative tissue sections from these sarcomas were analysed by immunohistochemistry using a well-characterised anti-pRB monoclonal antibody. Tumours were considered to have a positive pRB phenotype only when pure nuclear staining was demonstrated, and cases were segregated into one of three groups. Group 1 (n = 36) were patients whose tumours have minimal or undetectable pRB nuclear staining (< 20% of tumour cells) and were considered pRB negative. Patients with tumours staining in a heterogeneous pattern (20-79% of tumour cells) were classified as group 2 (n = 99). The staining of group 3 (n = 39) was strongly positive with a homogeneous pRB nuclear immunoreactivity (80-100% of tumour cells). pRB alterations were frequently observed in both low- and high-grade lesions. Altered pRB expression did not correlate with known predictors of survival and was not itself an independent predictor of outcome in the long-term follow-up. These findings support earlier observations that alterations of pRB expression are common events in soft-tissue sarcomas; nevertheless, long-term follow-up results indicate that altered patterns of pRB expression do not influence clinical outcome of patients affected with soft-tissue sarcomas. It is postulated that RB alterations are primary events in human sarcomas and may be involved in tumorigenesis or early phases of tumour progression in these neoplasias.

The nuclear tyrosine kinase Rak associates with the retinoblastoma protein pRb.

Rak is a nuclear tyrosine kinase containing Src homology 2 and 3 domains at its NH2 terminus. We report here that the retinoblastoma tumor susceptibility gene product pRb associates with Rak in vivo and in vitro. Rak binds in the A/B pocket region of pRb, a region that is frequently mutated in human cancer, during the G1 and S phases of the cell cycle. Furthermore, Rak expression is elevated in G1, and transfection of Rak into NIH 3T3 cells results in a significant decrease in the number of emerging colonies. Thus, Rak is a tyrosine kinase with growth suppressing activity that may function, in part, through its interaction with pRb.