Phase I trial of gemcitabine in patients with advanced pancreatic cancer

BACKGROUND

Gemcitabine is the most promising new agent currently being tested in pancreatic cancer. The present study was conducted to confirm the tolerability of a weekly schedule of gemcitabine at a dose of 1000 mg/m2 in Japanese patients with advanced pancreatic cancer.

METHODS

The primary end-point was to evaluate the frequency of dose-limiting toxicity. Gemcitabine 1000 mg/m2 was administered over 30 min weekly in two schedules: gemcitabine x3 every 4 weeks (Schedule 1) and gemcitabine x7 followed by a week of rest and then gemcitabine x3 every 4 weeks thereafter (Schedule 2). At least three patients entered each schedule and three additional patients were treated in the presence of dose-limiting toxicity.

RESULTS

Eleven chemo-naive patients with a good Karnofsky performance status of > or =80 points and distant metastasis were entered into this trial. In Schedule 1, no dose-limiting toxicity was observed in the three patients. In Schedule 2, the evaluation of dose-limiting toxicity was complete in six of the eight enrolled patients and two patients showed dose-limiting toxicity in this Schedule; one patient experienced both grade 4 leukocytopenia and grade 4 neutropenia, and both grade 4 neutropenia and grade 3 GOT/GPT increased in another patient. Two patients (18%) showed a partial response and a clinical benefit response was also achieved in two (29%) of the seven evaluable patients.

CONCLUSION

Gemcitabine 1000 mg/m2 weekly x7 followed by a week of rest and weekly x3 every 4 weeks thereafter may be tolerated in Japanese patients with advanced pancreatic cancer.

Hepatic arterial infusion of 5-fluorouracil for liver metastases from pancreatic carcinoma: results from a pilot study

BACKGROUND/AIMS

Liver metastasis is a common progression of pancreatic carcinoma, but an effective chemotherapy has not been established. The purpose of this study was to examine the efficacy and safety of a hepatic arterial infusion of 5-FU in patients with liver metastasis from pancreatic carcinoma.

METHODOLOGY

Thirteen patients were enrolled in a pilot study of a hepatic arterial infusion of 5-FU therapy. They received 5-FU for 5 days at a dose of 500 mg/m2/day by continuous hepatic arterial infusion every 4 weeks.

RESULTS

One patient showed a partial response, while 6 showed no change. Of these 6 patients, 2 showed a minor response. The overall response rate was 8% (95% confidence interval: 0-22%). Nausea and vomiting were the most common types of toxicity. Three patients (23%) had hepatic arterial occlusion. There were no life-threatening toxicities or complications. The overall median survival time was 15.9 weeks.

CONCLUSIONS

Hepatic arterial infusion of 5-FU in patients with liver metastasis from pancreatic carcinoma is tolerable but is minimally effective at this dose and schedule. The schedule of administration should be modified.

Assessment of arterial tumor vascularity in small hepatocellular carcinoma. Comparison between color doppler ultrasonography and radiographic imagings with contrast medium: dynamic CT, angiography, and CT hepatic arteriography

Hepatocellular carcinoma (HCC) is characterized by tumor vascularization from the hepatic artery. The objective of our work was to compare color Doppler ultrasonography (CDU), including power Doppler ultrasonography (PDU) with radiographic imagings with contrast medium in regard to the detection of the arterial tumor vascularity of small hepatocellular carcinomas (HCC). We examined 42 small HCC lesions 2 cm or less in diameter in 37 patients for arterial tumor vascularity by conventional CDU, PDU, dynamic computed tomography (dCT), digital subtraction angiography (DSA), and CT hepatic arteriography (CTA). Color images were detected in 25 (59.5%) and 28 (66.7%) of the 42 lesions with conventional CDU and PDU, respectively, and tumor vascularity was detected in 26 (61.9%) by dCT, 23 (54.8%) by DSA, and 29 (69.0%) by CTA. Tumor vascularity could be detected in 51.9% by PDU and CTA, more than by conventional CDU, dCT, and DSA (44.4, 44.4, and 33.3%, respectively) in well-differentiated HCC, whereas the detection rates by these techniques were almost equal (86.7% by CDU, 93.3% by PDU, dCT, and DSA, 100% by CTA, respectively) in moderately and poorly differentiated HCC. PDU is superior to CDU, dCT and DSA and equal to CTA for the detection of tumor vascularity in small HCC, particularly in well-differentiated HCC.

An oncogenic form of the Flt-1 kinase has a tubulogenic potential in a sinusoidal endothelial cell line

We have previously reported a constitutively activated form of the Flt-1 kinase (BCR-FLTm) molecularly engineered based on the structural backbone of the activated tyrosine kinase BCR-ABL. Here we show that it can induce not only growth stimulation but also tubulogenic differentiation of non-tubulogenic NP31 (non parenchymal) sinusoidal endothelial cells of rat liver in basement membrane matrix. Tubules formed in vitro were accompanied by fenestration structures and allowed circulation when transplanted into syngeneic animals. This biological response was not observed in other activated forms of kinases constructed in a similar fashion, which include Trk (BCR-TRK), KDR (BCR-KDR), and the parental BCR-ABL. Interestingly, formation of fine tubules was accomplished with lower but not higher expression levels of BCR-FLTm. Compared to NP cells in primary culture NP31 is deficient in expression of alpha1 integrin subunit, which was restored by expression of BCR-FLTm that had tubulogenic ability. Matrix-induced tyrosine phosphorylation of an adaptor protein Shc with recruitment of Grb-2 was observed even when tubulogenesis was nearly completed at G1 stage of the cell cycle in 2-3 weeks. Activation of matrix metalloproteinase 2 (MMP-2) and expression of urokinase type plasminogen activator (uPA) was observed with cellular invasion into matrix at the depth of 200-300 microm. Inhibitors for MAP kinase activator MEK1 and for serine proteases showed deleterious effects on the tubulogenesis. We suppose that matrix ligand-induced integrin signals cooperate with a low level of Flt-1 kinase activity to promote tubulogenic behaviors of endothelial cells in this system.

[Tumor progression and angiogenesis]

Vascular endothelial growth factor (VEGF) plays a central role in angiogenesis, which underlies tumor progressions such as metastasis. A unique biological feature is that VEGF, mainly produced by malignant cells, hits seemingly non-malignant endothelial cells of host origin. The expression level of VEGF or its receptors appears to be regulated by intrinsic factors such as genetic alterations as well as by extrinsic factors such as pO2 and cytokines. Receptor signals result in coordinated regulation of molecules responsible for growth, differentiation, matrix degradation, migration, adhesion, coagulation, permeability and so forth.

BCR binds to the xeroderma pigmentosum group B protein

The BCR gene is involved in the formation of the BCR-ABL oncogene responsible for the pathogenesis of Philadelphia chromosome-positive human leukemias. We have previously shown that P210 BCR-ABL binds to the xeroderma pigmentosum group B protein (XPB) through the portion of BCR that is homologous to the catalytic domain of GDP-GTP exchangers such as yeast CDC24 and Dbl. In the baculovirus overexpression system which facilitates binding of coexpressed proteins, we now show that XPB binds to the intact BCR protein efficiently but not to CDC24 or Dbl, suggesting specificity of this interaction. The binding of endogenous BCR and XPB proteins was also detected in Hela cells, and this was inhibited by a blocking peptide. Full-length (1-782) XPB and its truncated form (203-782), which does not contain the nuclear localization signal, were tagged with glutathione S-transferase (GST) and were expressed in Rat1 fibroblasts. GST-XPB(203-782) was localized predominantly in the cytoplasm and bound to BCR but not to p62, one of the other components in TFIIH. GST-XPB(1-782) was largely in the nucleus and bound to p62 and BCR. Although the biological significance of the binding remains to be uncovered, BCR binds to the XPB/p62 complex.

Clinical significance of magnetic resonance cholangiopancreatography for the diagnosis of cystic tumor of the pancreas compared with endoscopic retrograde cholangiopancreatography and computed tomography

BACKGROUND

Cystic tumor of the pancreas has been investigated by a variety of imaging techniques. Magnetic resonance cholangiopancreatography (MRCP) is being widely used as a non-invasive diagnostic modality for investigation of the biliary tree and pancreatic duct system. The purpose of this study was to compare MRCP images with those of endoscopic retrograde cholangiopancreatography (ERCP) and computed tomography (CT) in order to clarify the diagnostic efficacy of MRCP for cystic tumor of the pancreas.

METHODS

We retrospectively studied 15 patients with cystic tumor of the pancreas that had been surgically resected and histopathologically confirmed. There were five cases of intraductal papillary adenocarcinoma, five of intraductal papillary adenoma, two of serous cyst adenoma, two of retention cyst associated with invasive ductal adenocarcinoma and one of solid cystic tumor.

RESULTS

In all cases MRCP correctly identified the main pancreatic duct (MPD) and showed the entire cystic tumor and the communication between the tumor and the MPD. On the other hand, the detection rate by ERCP of the cystic tumor and the communication between the cystic tumor and the MPD was only 60%. Although the detection rates by CT for the septum and solid components inside the cystic tumor were 100 and 90.0%, respectively, those of MRCP for each were 58.3 and 20.0%.

CONCLUSION

MRCP is capable of providing diagnostic information superior to ERCP for the diagnosis of cystic tumor of the pancreas. Although MRCP may provide complementary information about the whole lesion of interest, the characteristic internal features of cystic tumor of the pancrease should be carefully diagnosed in combination with CT.

Quantification of hepatitis C virus by TaqMan PCR: comparison with HCV Amplicor Monitor assay

The quantitation of serum levels of hepatitis C virus RNA in chronic hepatitis C has been regarded as one of the most important indicators for the outcome of interferon therapy. A new method was used for quantitating the copy number of hepatitis C virus RNA using TaqMan polymerase chain reaction and for comparing the ability and usefulness of this assay with Amplicor Monitor assay in 138 patients. The detection range of hepatitis C virus RNA by TaqMan polymerase chain reaction was from 2 x 10(3) to 2 x 10(8) copies/ml. Hepatitis C virus RNA was detectable in 128 cases (92.8%) and undetectable in 10 cases (7.2%) by this method. The RNA levels measured by Amplicor Monitor assay correlated significantly with those measured by TaqMan polymerase chain reaction assay and the sensitivity of the two assays was almost equal. Thus, TaqMan polymerase chain reaction assay appears sufficiently sensitive for the evaluation of hepatitis C virus RNA and would be useful for the diagnosis and management of hepatitis C virus infection.

Detection of bile duct cancer by autofluorescence cholangioscopy: a pilot study

BACKGROUND/AIMS

There is increasing interest in the detection of malignancy by autofluorescence endoscopy. This is the first report on autofluorescence endoscopy in bile duct cancer.

METHODOLOGY

Nine patients with bile duct cancer underwent percutaneous transhepatic autofluorescence cholangioscopy using light-induced fluorescence endoscopy in the gastrointestinal tract (LIFE-GI) system.

RESULTS

The cancerous lesion had quite a different color in comparison with normal mucosa, which was seen as light blue, by the autofluorescence endoscopy. In all patients, cancerous legions were observed as dark red. Additionally, in 7 of the 9 cases a white fluorescence was also seen in the cancerous lesion.

CONCLUSIONS

In previous reports on the gastrointestinal tract and bronchial tree, cancerous lesions appeared dark red when examined by autofluorescence endoscopy. In our study, it is suggested that a white fluorescence is also an important finding for making diagnosis of bile duct cancer by the autofluorescence endoscopy.

The BCR-ABL oncoprotein potentially interacts with the xeroderma pigmentosum group B protein

The previously uncharacterized CDC24 homology domain of BCR, which is missing in the P185 BCR-ABL oncogene of Philadelphia chromosome (Ph1)-positive acute lymphocytic leukemia but is retained in P210 BCR-ABL of chronic myelogeneous leukemia, was found to bind to the xeroderma pigmentosum group B protein (XPB). The binding appeared to be required for XPB to be tyrosine-phosphorylated by BCR-ABL. The interaction not only reduced both the ATPase and the helicase activities of XPB purified in the baculovirus system but also impaired XPB-mediated cross-complementation of the repair deficiency in rodent UV-sensitive mutants of group 3. The persistent dysfunction of XPB may in part underlie genomic instability in blastic crisis.

Virally activated Ras cooperates with integrin to induce tubulogenesis in sinusoidal endothelial cell lines

Four cell lines, named nonparenchymal 11 (NP11), NP26, NP31, and NP32, were established from sinusoidal endothelial cells (SECs) of rat liver. They still retained expression of receptors for vascular endothelial growth factor (VEGF), Fit-1, and kinase domain-containing receptor (KDR). NP31 and NP32 turned out to be incapable of tubulogenesis in basement membrane matrix (Matrigel), which belongs to endothelial properties, as shown by SECs in primary culture. Expression of temperature-sensitive, virally activated Ras (ts-v-Ras) restored tubulogenic behaviors back to NP31 only at permissive temperature. Matrigel induced long-lasting tyrosine phosphorylation of Shc, with recruitment of Grb-2 and microtubule-associated protein kinase (MAPK) activation in both parental NP31 and NP31 transformed by ts-v-Ras, which was blocked by anti-beta1 integrin antibody. Tubulogenesis was inhibited by adenovirus-mediated expression of dominant-negative Ras in human umbilical vein endothelial cells (HUVECs). PD 098059, a selective inhibitor of MAPK kinase (MEK), nearly perfectly blocked tubulogenesis by ts-v-Ras-expressing NP31 cells at permissive temperature. Furthermore, the botulinum C3 toxin, an inhibitor for Rho, caused fragmentation of branching cords in networks formed by NP31 that expressed ts-v-Ras at permissive temperature. These data suggest that the integrin-mediated Ras signals may be necessary but are not sufficient for tubulogenesis and that an artificial expression of v-Ras might substitute for the second signal required in this system.

Flt-1, a receptor for vascular endothelial growth factor, has transforming and morphogenic potentials

A paradox of Flt-1, a tyrosine kinase receptor for vascular endothelial growth factor (VEGF), is that the ligand cannot activate the receptor to stimulate growth of cells that exogenously overexpress the receptor. In order to find Flt-1 kinase-dependent biological systems, we obtained for the first time activated forms of the Flt-1 kinase in a ligand-independent manner. Replacement of the ABL sequences in the human leukemia oncoprotein BCR-ABL with the cytoplasmic domain of Flt-1 (BCR-FLT) followed by a retroviral random mutagenesis scheme gave constitutively active artificial chimera BCR-FLTm with mutations within the Flt-1 sequence. Like BCR-ABL it could, but not the original BCR-FLT, transform Rat1 fibroblasts, abrogate cytokine dependence in Ba/F3 cells, and induce neurite-like structures in neuronal PC12 cells. Interestingly, Rat1 cells transformed by BCR-FLTm formed tube-like structures in basement membrane matrix. BCR-FLTm retroviruses may be a very useful tool to investigate an as yet uncovered functions of the Flt-1 kinase.

Detection of GBV-C RNA in patients with non-A-E fulminant hepatitis by reverse-transcription polymerase chain reaction

GBV-C might be a causative agent of fulminant hepatitis of unknown etiology. Fulminant hepatitis is an indication for liver transplantation. However, in Japan, because of the legal difficulties associated with cadaveric donation, patients with fulminant hepatitis are still treated by plasmapheresis and multiple transfusions of fresh frozen plasma. So, the possibility that GBV-C might be transmitted by transfusions after the onset of fulminant hepatitis is real. Therefore, we have examined the possible role of GBV-C in non-A-E fulminant hepatitis. Nine patients with non-A-E fulminant hepatitis and one with non-A-E late onset hepatic failure were examined. Sera were obtained from the patients at admission before any blood or blood products were given, and again after transfusions. GBV-C RNA was detected by nested reverse transcription polymerase chain reaction with primers based on the reported sequence. GBV-C RNA was negative in all 10 pretransfusion patients with non-A-E fulminant hepatitis or late onset hepatic failure. Then, fresh frozen plasma was transfused to these patients, and four of them became seropositive. GBV-C is unlikely to be a major etiologic agent for non-A-E fulminant hepatitis in Japan.

BCR-ABL induces neurite-like structures and BCR lacking the SH2-binding domain induces cell rounding in PC12 cells

The activated tyrosine kinase oncoprotein BCR-ABL is responsible for pathogenesis of Philadelphia chromosome-positive human leukemias. Because BCR carries a GAP (GTPase-activating protein) activity toward cytoskeleton-related small GTP-binding proteins, we utilized a neuronal PC12 cell system to test morphogenic potentials of BCR-ABL or BCR. We report here unique morphological phenotypes of PC12 cells expressing either BCR-ABL or a BCR mutant which lacks the SH2-binding domain (BCR Delta162-413). Although MAP kinase was not activated in PC12 cells expressing BCR-ABL, they showed incomplete neurite extensions even in the absence of the nerve growth factor (NGF). Overproduction of BCR Delta162-413 in PC12 cells, on the other hand, induced cell rounding in the absence of NGF. Interestingly, those cells could hardly make terminal differentiation in the presence of NGF and continued to grow without changing their round shape, although NGF receptor as well as MAP kinase appeared to be activated. Interestingly, the botulinum C3 toxin induced neurite-like structures in PC12 cells overexpressing BCR Delta162-413 without NGF.

The dimerization property of glutathione S-transferase partially reactivates Bcr-Abl lacking the oligomerization domain

Bcr-Abl oncoproteins are responsible for the pathogenesis of human leukemias with a reciprocal chromosome translocation t(9;22). The amino-terminal Bcr sequence has a potential to form a homotetramer (tetramer domain), and destructions of the tetramer domain cause a complete loss of biological activities in Bcr-Abl. Here we show that Bcr-Abl in which the tetramer domain is replaced with glutathione S-transferase (GST) with a dimerizing ability (GST/Bcr-Abl-(Delta1-160)) can no longer induce an interleukin-3 (IL-3) independence in Ba/F3 cells or transform mouse bone marrow cells but still retains by 30-40% the ability to transform Rat1 cells. Compared with the wild type Bcr-Abl, autophosphorylation of GST/Bcr-Abl-(Delta1-160) in vivo was reduced by more than 50%. The Grb-2 binding to GST/Bcr-Abl-(Delta1-160) was 50% reduced in Rat1 cells and undetectable in Ba/F3 cells. In Rat1 cells expressing GST/Bcr-Abl-(Delta1-160), phosphotyrosine contents of p62 and Shc were 70% decreased.

Deletion of the ABL SH3 domain reactivates de-oligomerized BCR-ABL for growth factor independence

Biological activities of BCR-ABL, an activated tyrosine kinase oncogene responsible for pathogenesis of human leukemias, can be completely inactivated by a deletion of the BCR aminoterminal sequence with tetramerizing property (BCR-ABL delta 1-40). We attempted several ways to restore the ability to induce growth factor independence to the de-oligomerized BCR-ABL delta 1-40 and found that an additional deletion of the ABL SH3 domain could. In BCR-ABL delta 1-40 reactivated by the SH3 deletion, transphosphoryation of other cellular proteins like p62 or SHC in vivo and autophosphorylation with recruitment of GRB-2 were also recovered.

Tyrosine phosphorylation of BCR by FPS/FES protein-tyrosine kinases induces association of BCR with GRB-2/SOS

The human bcr gene encodes a protein with serine/threonine kinase activity, CDC24/dbl homology, a GAP domain, and an SH2-binding region. However, the precise physiological functions of BCR are unknown. Coexpression of BCR with the cytoplasmic protein-tyrosine kinase encoded by the c-fes proto-oncogene in Sf-9 cells resulted in stable BCR-FES protein complex formation and tyrosine phosphorylation of BCR. Association involves the SH2 domain of FES and a novel binding domain localized to the first 347 amino acids of the FES N-terminal region. Deletion of the homologous N-terminal BCR-binding domain from v-fps, a fes-related transforming oncogene, abolished transforming activity and tyrosine phosphorylation of BCR in vivo. Tyrosine phosphorylation of BCR in v-fps-transformed cells induced its association with GRB-2/SOS, the RAS guanine nucleotide exchange factor complex. These data provide evidence that BCR couples the cytoplasmic protein-tyrosine kinase and RAS signaling pathways.

A unique signal transduction from FLT tyrosine kinase, a receptor for vascular endothelial growth factor VEGF

Flt-1 (fms-like tyrosine kinase-1), a receptor-type tyrosine kinase of sharing similar features with two other flt-family encoded proteins KDR/Flk-1 and Flt-4, has been recently identified as a receptor for Vascular Endothelial Growth Factor (VEGF) known to induce the proliferation of vascular endothelial cells. In this study, we demonstrate that Flt-1 encodes for a 180 kDa glycoprotein, binds VEGF with high affinity, undergoes autophosphorylation but does not generate any mitogenic response in transfected NIH3T3 fibroblasts. Interestingly, the immediate early gene c-myc was not induced, whereas the c-fos was induced very weakly in Flt-1 expressing NIH3T3 cells. A comparative analysis of the Flt-1 signal cascade in the environment of endothelial cells with that of Flt-1 expressing NIH3T3 cells showed that VEGF induced phosphorylation of PLC gamma and GAP complex on tyrosine in both type of cells. However, a strong activation of MAP kinases was observed only in endothelial cells. Further, different from many other receptor tyrosine kinases, tyrosine phosphorylation of Shc protein, an important adaptor for signal transduction from many receptor kinases, was very weak in both Flt-1-NIH3T3 cells and endothelial cells. These results suggest that Flt-1 kinase utilizes a unique signal transduction system in endothelial cells, and the activation of the Flt-1 kinase is insufficient to trigger a mitogenic response in NIH3T3 fibroblasts.

Differently spliced cDNAs of human leukocyte tyrosine kinase receptor tyrosine kinase predict receptor proteins with and without a tyrosine kinase domain and a soluble receptor protein

Leukocyte tyrosine kinase (LTK) is a tyrosine kinase that has been suggested to be specific for hematopoietic cells and neuronal cells and reported as an unusual membrane protein lacking an extracellular domain. Here we report the cloning of a human LTK cDNA clone containing the complete open reading frame of a putative receptor tyrosine kinase protein. The extracellular domain of the receptor protein is larger than previously predicted. Furthermore, we have cloned a set of cDNAs representing differently spliced human LTK mRNAs. These cDNAs predict a truncated receptor protein lacking the tyrosine kinase domain and a soluble receptor protein that has neither a transmembrane nor a tyrosine kinase domain. Our results suggest that the LTK gene produces not only the putative receptor tyrosine kinase for unknown ligand but also multiple protein products that may have different functions.

A GDP dissociation inhibitor that serves as a GTPase inhibitor for the Ras-like protein CDC42Hs

Members of the family of Ras-related guanosine triphosphate (GTP) binding proteins appear to take part in the regulation of a number of biological processes, including cell growth and differentiation. Three different classes of proteins that regulate the GTP binding and GTP hydrolytic activities of the Ras family members have been identified. These different regulatory proteins inhibit guanosine diphosphate (GDP) dissociation (designated as GDIs), stimulate GDP dissociation and GDP-GTP exchange (designated as GDSs), or stimulate GTP hydrolysis (designated as GAPs). In the case of the Ras-like protein CDC42Hs, which is the human homolog of a Saccharomyces cerevisiae cell division cycle protein, the GDI protein also inhibited both the intrinsic and GAP-stimulated hydrolysis of GTP. These findings establish an additional role for the GDI protein--namely, as a guanosine triphosphatase (GTPase) inhibitory protein for a Ras-like GTP binding protein.

The BCR gene encodes a novel serine/threonine kinase activity within a single exon

Sequences encoded by the first exon of BCR that bind to the ABL SH2 domain are essential for the activation of the ABL tyrosine kinase and transforming potential of the chimeric BCR-ABL oncogene. The normal cellular BCR gene encodes a 160,000 dalton phosphoprotein associated with a serine/threonine kinase activity, but it shows only weak dispersed homologies to protein kinases. p160c-BCR was purified to apparent homogeneity as an oligomer of greater than 600,000 daltons that contains autophosphorylation activity and transphosphorylation activity for several protein substrates. A region containing paired cysteine residues within the 426 amino acids encoded by the first exon of BCR is essential for its novel phosphotransferase activity, which overlaps with the strong SH2-binding regions. The recent demonstration of a GTPase-activating function within the C-terminal portion of BCR suggests that the protein kinase and SH2-binding domains may work in concert with other regions of the molecule in intracellular signalling processes.

BCR sequences essential for transformation by the BCR-ABL oncogene bind to the ABL SH2 regulatory domain in a non-phosphotyrosine-dependent manner

BCR-ABL is a chimeric oncogene implicated in the pathogenesis of Philadelphia chromosome-positive human leukemias. BCR first exon sequences specifically activate the tyrosine kinase and transforming potential of BCR-ABL. We have tested the hypothesis that activation of BCR-ABL may involve direct interaction between BCR sequences and the tyrosine kinase regulatory domains of ABL. Full-length c-BCR as well as BCR sequences retained in BCR-ABL bind specifically to the SH2 domain of ABL. The binding domain has been localized within the first exon of BCR and consists of at least two SH2-binding sites. This domain is essential for BCR-ABL-mediated transformation. Phosphoserine/phosphothreonine but not phosphotyrosine residues on BCR are required for interaction with the ABL SH2 domain. These findings extend the range of potential SH2-protein interactions in growth control pathways and suggest a function for SH2 domains in the activation of the BCR-ABL oncogene as well as a role for BCR in cellular signaling pathways.

Overexpression confers an oncogenic potential upon the eph gene

The eph gene encodes a putative receptor tyrosine kinase for an as yet unknown ligand. Some human cancer cells have been found to overexpress eph mRNAs without gene amplification. We show here that NIH3T3 cells acquire tumorigenic ability in nude mice and make colonies in soft agar with a viral LTR (Long Terminal Repeat)-driven artificial expression of the eph gene to a high level. This result supports the alleged contribution of overexpressed receptor tyrosine kinases to cell transformation.

Evolution, expression, and chromosomal location of a novel receptor tyrosine kinase gene, eph

Partial sequence analysis of the genomic eph locus revealed that the splicing points of kinase domain-encoding exons were completely distinct from those of the other protein tyrosine kinase members reported, suggesting that this is the earliest evolutionary split within this family. In Northern (RNA) blot analysis, the eph gene was expressed in liver, lung, kidney, and testis of rat, and screening of 25 human cancers of various cell types showed preferential expression in cells of epithelial origin. Overexpression of eph mRNA was found in a hepatoma and a lung cancer without gene amplification. Comparison of cDNA sequences derived from a normal liver and a hepatoma that overproduces eph mRNA demonstrated that two of them were completely identical throughout the transmembrane to the carboxy-terminal portions. Southern blot analysis of DNAs from human-mouse hybrid clones with an eph probe showed that this gene was present on human chromosome 7.