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Original Article |

G Protein γ7 Expression as a New Clinicopathological Marker in Patients With Intrahepatic Cholangiocarcinoma FREE

Tohru Utsunomiya, MD; Hiroshi Inoue, MD; Ken-Ichi Taguchi, MD; Mitsuo Shimada, MD; Keizo Sugimachi, MD; Masaki Mori, MD
[+] Author Affiliations

From the Department of Surgery, Medical Institute of Bioregulation, Kyushu University, Beppu, Japan (Drs Utsunomiya, Inoue, and Mori); and the Departments of Anatomic Pathology (Dr Taguchi) and Surgery and Science (Drs Shimada and Sugimachi), Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.


Arch Surg. 2002;137(2):181-185. doi:10.1001/archsurg.137.2.181.
Text Size: A A A
Published online

Hypothesis  The signal alterations mediated by small G proteins such as Ras, Rho, and Rac have been reported in several cancers. The human G protein γ7 (G7) gene, which is down-regulated in various digestive organ cancers, was recently identified and cloned. Thus, the G-γ7–coupled heterotrimeric G proteins may also contribute to carcinogenesis in human cancers.

Setting  University hospital and medical institute of bioregulation.

Patients and Methods  The clinicopathological significance of G-γ7 expression in 18 patients with intrahepatic cholangiocarcinoma (IHCC) was examined. The tumor-nontumor ratio of G-γ7 expression was determined using reverse transcription polymerase chain reaction analysis. To visualize the localization of G-γ7, an immunohistochemical study was performed.

Main Outcome Measure  Clinicopathological significance of G7 expression in human IHCC.

Results  Expression of G-γ7 messenger RNA was lower in tumor tissue than in the corresponding nontumor tissue in 17 (94%) of 18 patients with IHCC. The mean tumor-nontumor ratio was 0.54. Eleven patients with tumor-nontumor ratios less than 0.5 showed significantly poorer differentiated IHCC than 7 with tumor-nontumor ratios of 0.5 and greater (P<.01). Decreased expression of G-γ7 protein in the carcinoma tissue, especially in the poorly differentiated IHCC tissue, was confirmed using immunohistochemical staining.

Conclusions  Reduced expression of G-γ7 is associated with the histological grade of IHCC and may therefore prove to be a useful marker for predicting the biological aggressiveness of human IHCC.

Figures in this Article

THE TECHNIQUES of subtractive complementary DNA cloning and differential display between tumor and normal tissue samples of gastrointestinal tract cancers have been used to determine new clinicopathological and prognostic molecular markers.13 Accordingly, Shibata et al4 recently identified and cloned the human G protein γ7 (G7) gene, which is down-regulated in pancreatic cancer and cell lines. Shibata et al5 further confirmed a decrease in the expression of G-γ7 in other gastrointestinal tract cancers, including esophageal, gastric, and colorectal cancers.

Heterotrimeric G protein, which is composed of α, β, and γ subunits, transduces the signals across the plasma membrane from a receptor to an effector.68 The signal-transducing elements of the G protein are not only the α subunit that binds and hydrolyzes guanosine 5′-triphosphate, but also the β γ subunit, which plays a major role in signal transmission.9,10 To date, 7 β subunits and 11 γ subunits have been identified in mammalian systems.11 The G protein γ subunits determine the functional specificity and stabilize the heterotrimeric G protein to the cellular membrane.6,12,13 Although the signal alterations mediated by small G proteins such as Ras,14 Rho,15,16 and Rac15 have been reported in several cancers, little information is available on the changes in the mediated signals of heterotrimeric G proteins in cancer. Because the G protein β γ subunit clearly controls the signals involved in cell growth17 and the G7 gene is widely distributed in the signal transduction pathways,18,19 the G-γ7–coupled G proteins may contribute to carcinogenesis in many kinds of cancers.

In a previous study, Shibata et al5 transfected the G-γ7 complementary DNA into a human esophageal carcinoma cell line to determine its biological role in cancer. Expression of G-γ7 suppressed cell growth when the cells were confluent. Moreover, G-γ7 expression suppressed tumorigenicity in nude mice, thus implicating the biological effects of G-γ7 in vivo. All these findings prompted us to analyze the clinical significance of this gene in human cancer. In the present study, we determined G-γ7 expression and its clinical significance in patients with intrahepatic cholangiocarcinoma (IHCC) who underwent hepatic resection. This study showed a significant association between G-γ7 expression and the histological grade of IHCC, which is one of the most important prognostic factors for patients with IHCC.20,21

CLINICAL SAMPLES AND CELL LINES

Eighteen patients with IHCC who underwent surgery at the Medical Institute of Bioregulation Hospital and the Department of Surgery and Science, Kyushu University, were studied. All 18 patients underwent hepatectomies for primary tumors. No patients demonstrated complications with either hepatolithiasis or primary sclerosing cholangitis. After the hepatectomies, the tumor and corresponding nontumor tissues were immediately frozen in liquid nitrogen and kept at −90°C until use. Written informed consent was obtained from all patients. The study was performed according to the latest revision of the Helsinki Declaration (1989) for human research. The human bile duct cancer cell lines, HuCC-T1, TFK-1, and HuH28, were provided by the Cell Resource Center for Biomedical Research, Institute of Development, Aging and Cancer, Tohoku University, Tohoku, Japan.

RNA EXTRACTION

Total RNA was prepared using a modification of the guanidinium thiocyanate method described elsewhere.1,2 To avoid contamination by genomic DNA, 50 µg of total RNA was treated with 1 U of deoxyribonuclease I (Message Clean Kit; Gene Hunter, Nashville, Tenn). The treated RNAs were dissolved to 1 µg/µL using diethylpyrocarbonate-treated water and then were stored at −90°C until use.

REVERSE TRANSCRIPTION POLYMERASE CHAIN REACTION ANALYSIS

Complementary DNA was synthesized from 2.5 µg of total RNA.4,5,22 The oligonucleotide primer pairs for G-γ7 were synthesized (sense primer: 5′-GTCAACGGATTTGGTCTGTAT-3′; antisense primer: 5′-AGTCTTCTGGGTGGCAGTGAT-3′). Polymerase chain reaction (PCR) was performed using a method described previously.4,5,22 To ensure that the RNA was of sufficient purity for reverse transcription (RT)-PCR, a PCR assay with primers specific for the gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) complementary DNA was carried out in each case. Aliquots of the PCR-amplified DNA were electrophoresed on 1.5% agarose gels containing ethidium bromide. Expression of G-γ7 and GAPDH was evaluated by computer-assisted image analysis. The tumor-nontumor ratio (T/N ratio) of G-γ7 expression was calculated after correcting for the T/N ratio of GAPDH expression. Values of 0.5 or greater were considered positive, and values less than 0.5 were considered negative.

IMMUNOHISTOCHEMICAL STAINING

All samples for immunohistochemical staining were fixed in buffered formalin, embedded in paraffin, and cut into 5-µm-thick slices. The G-γ7 protein was detected using antibovine G-γ7 (Santa Cruz Biotechnology Inc, Santa Cruz, Calif) followed by the streptavidin-biotin-peroxidase method (LSAB Kit; DAKO Japan Co, Ltd, Kyoto, Japan), as described previously.4,5,23

CLINICOPATHOLOGICAL DATA

All the clinical data variables were available for evaluation. The clinicopathological features were evaluated according to the General Rules for the Clinical and Pathological Study of Primary Liver Cancer.24 The data were then compared between G-γ7–positive and G-γ7–negative patients.

STATISTICAL ANALYSIS

For continuous variables, data are expressed as mean ± SD. To compare the clinicopathological characteristics between the 2 patient groups, either the unpaired t test or the χ2 test was used. A 2-sided P<.05 was considered significant.

G-γ7 EXPRESSION BY RT-PCR

The T/N ratios of G-γ7 messenger RNA (mRNA), which were corrected for those of GAPDH mRNA, ranged from 0.20 to 1.69 (mean, 0.54) and were larger than 1.0 in only 1 patient (6%) (Table 1). Consistent with previous findings in other gastrointestinal tract cancers,5 expression of G-γ7 mRNA in IHCC was markedly lower in tumor tissues than in the corresponding nontumor tissues. Figure 1 shows representative patients. All 3 cell lines (HuCC-T1, TFK-1, and HuH28) showed no expression of G-γ7 mRNA by RT-PCR (Figure 2), which is also consistent with findings from a previous study4 of the pancreatic cancer cell lines.

Table Graphic Jump LocationTable 1. G Protein γ7 Gene Expression and the Histological Grade of Intrahepatic Cholangiocarcinoma*
Place holder to copy figure label and caption
Figure 1.

Reverse transcription polymerase chain reaction of G protein γ7 (G-γ7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in 5 representative patients. Expression of G-γ7 was suppressed in the tumor tissues. The evaluated tumor-nontumor ratios of G-γ7 messenger RNA, which were corrected for the tumor-nontumor ratios of GAPDH messenger RNA, were 0.56, 0.30, 0.20, 0.29, and 0.22 in lanes 1 through 5, respectively. M indicates marker; T, tumor tissue; and N, nontumor tissue.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Expression of G protein γ7 (G-γ7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in 1 tumor tissue (lane 1), 1 nontumor tissue (lane 2), and 3 bile duct cancer cell lines (lane 3, HuCC-T1; lane 4, TFK-1; and lane 5, HuH28). None of the 3 bile duct cancer cell lines expressed the amplified DNA. M indicates marker.

Graphic Jump Location
IMMUNOHISTOCHEMICAL STAINING

Staining of G-γ7 was markedly weaker in IHCC tissue than in the corresponding nontumor hepatic tissue in moderately differentiated and poorly differentiated IHCC (Figure 3). Almost completely negative staining in poorly differentiated IHCC tissue was observed (Figure 3B). The immunohistochemical results closely corresponded with the RT-PCR results.

Place holder to copy figure label and caption
Figure 3.

Immunohistochemical staining for G protein γ7 in moderately differentiated (A) and poorly differentiated (B) intrahepatic cholangiocarcinoma. T indicates tumor tissue; N, nontumor tissue.

Graphic Jump Location
RT-PCR AND CLINICOPATHOLOGICAL DATA

The clinicopathological features analyzed in relation to the G-γ7 expression status are given in Table 2. The RT-PCR results indicated that 11 patients (61%) were negative and 7 (39%) were positive. There were no significant differences between G-γ7 expression and host factors, such as age, sex, and preoperative liver function test results. In contrast, G-γ7 expression strongly correlated with histological grade. In poorly differentiated IHCC tissues, G-γ7 expression was significantly lower than that in moderately differentiated IHCC tissues (P<.01). The histological grade of IHCC and the T/N ratio of G-γ7 expression in individual patients are listed in Table 1. However, other pathological variables, such as tumor diameter, intrahepatic metastasis, and lymph node metastasis, were not associated with the G-γ7 expression status.

Table Graphic Jump LocationTable 2. G Protein γ7 Gene Expression and the Clinicopathological Features of 18 Patients With Intrahepatic Cholangiocarcinoma*

Identification of the genes that are specifically expressed in either tumor or nontumor tissue is considered to be important for understanding the biological mechanisms of cancer. At our institution (Medical Institute of Bioregulation, Kyushu University), Shibata et al5 recently identified and cloned the human G7 gene, which is generally down-regulated in digestive organ cancers. In the present study, we thus studied the clinical significance of such G-γ7 expression in one type of human cancer: IHCC.

The signal alterations mediated by small G proteins in various cancers are already well known.1416 Regarding heterotrimeric G protein, the oncogenic mutations of G protein α subunit genes have also been documented in some endocrine tumors, including pituitary,25 adrenal,26 and thyroid27 tumors. However, to the best of our knowledge, there is no information on the oncogenic mutations of the G protein β γ subunits in human cancers. Shibata et al5 previously found that a stable transfection of a carcinoma cell line with a G-γ7 expression vector inhibited cell growth and tritiated thymidine uptake when the cells were 100% confluent. Furthermore, the G-γ7–induced G0/G1 arrest at high cell densities was associated with p27Kip1 expression. Our findings suggested that G-γ7–coupled heterotrimeric G proteins might transduce a growth inhibition signal with cell contact in normal cells, but this does not occur in cancer because of the inactivation of G-γ7.5 In the present study, we confirmed that the expression of G-γ7 mRNA was markedly suppressed in human IHCC tissue as well. This decreased gene expression significantly correlated with the histological grade of IHCC (Table 2). The results of immunohistochemical staining also indicated that G-γ7 expression in poorly differentiated IHCC was weaker than that in moderately differentiated IHCC. Although we are aware that only a few cases have been investigated, this is the first study, to our knowledge, to suggest that the signal alterations mediated by the β γ subunits of heterotrimeric G protein may affect the clinical features of human cancer.

The precise mechanisms by which the changes in the signaling pathway of G-γ7–coupled heterotrimeric G proteins were associated with the histological grade of IHCC remain to be established. However, according to the results of immunohistochemical analysis, the poorly differentiated IHCC with a solid pattern had an apparently higher cell density than the moderately differentiated IHCC with a granular pattern (Figure 3). It is possible that the G-γ7 signaling in poorly differentiated IHCC is inactivated even more than that in moderately differentiated IHCC because of the higher cell density. Alternatively, these tumor cells with a solid formation might be able to escape cell-cell contact-induced growth inhibition and even grow rapidly in the absence of or with a small presence of G-γ7 transduction signaling. On the other hand, Durand et al28 demonstrated that p27Kip1 protein level is high when the cells stop dividing and terminally differentiate during oligodendrocyte development, thus suggesting a strong correlation between cell differentiation and the accumulation of p27Kip1.29 Neural differentiation has also been reported to be responsible for the on-off switch of the expression of G protein γ subunits.30 Taken together, these findings, along with findings from a previous study of p27Kip1 expression in the G-γ7 transfectants,5 the markedly reduced signaling in the G-γ7 transduction pathway might also be associated with an absence of p27Kip1-induced growth arrest.

In conclusion, expression of G-γ7 mRNA was down-regulated in IHCC tissue and was clinically associated with the poorer histological grade of IHCC. Results of an immunohistochemical study also showed a drastically suppressed degree of staining in poorly differentiated IHCC tissue. The histological grade of IHCC is one of the most important prognostic factors for patients with IHCC.20,21 Therefore, the G-γ7 expression status may be a significant indicator for identifying the malignant biological behavior of human IHCC. However, the precise function of G-γ7 in IHCC tissue remains unclear. Further investigation is needed to clarify the relationship between G-γ7 and carcinoma progression.

We thank Kohei Shibata, MD, for helpful discussion and Kenji Sato, MS, Toshiko Shimooka, MS, Junko Miyake, MS, and Kazue Ogata, MS, for their excellent technical assistance.

Corresponding author and reprints: Masaki Mori, MD, Department of Surgery, Medical Institute of Bioregulation, Kyushu University, 4546 Tsurumibaru, Beppu 874-0838, Japan (e-mail: mmori@tsurumi.beppu.kyushu-u.ac.jp).

Mori  MStaniunas  RJBarnard  GFJessup  JMSteele  GD  JrChen  LB The significance of carbonic anhydrase expression in human colorectal cancer. Gastroenterology. 1993;105820- 826
Mori  MBarnard  GFStaniunas  RJJessup  JMSteele  GD  JrChen  LB Prothymosin-α mRNA expression correlates with that of c-myc in human colon cancer. Oncogene. 1993;82821- 2826
Shiraishi  TMori  MTanaka  SSugimachi  KAkiyoshi  T Identification of cystatin B in human esophageal carcinoma, using differential displays in which the gene expression is related to lymph-node metastasis. Int J Cancer. 1998;79175- 178
Link to Article
Shibata  KMori  MTanaka  SKitano  SAkiyoshi  T Identification and cloning of human G-protein K7, down-regulated in pancreatic cancer. Biochem Biophys Res Commun. 1998;246205- 209
Link to Article
Shibata  KTanaka  SShiraishi  TKitano  SMori  M G-protein K7 is down-regulated in cancers and associated with p27kip1-induced growth arrest. Cancer Res. 1999;591096- 1101
Rens  DSHamm  HE Structural and functional relationships of heterotrimeric G-proteins. FASEB J. 1995;91059- 1066
Nurnberg  BAhnert  HG Potential roles of heterotrimeric G proteins of the endomembrane systems. FEBS Lett. 1996;38961- 65
Link to Article
Wess  J G-protein–coupled receptors: molecular mechanisms involved in receptor activation and selectivity of G-protein recognition. FASEB J. 1997;11346- 354
Clapham  DENeer  EJ New roles for G-protein β K-dimers in transmembrane signaling. Nature (Lond). 1993;365403- 406
Link to Article
Muller  SLohse  MJ The role of G-protein β K subunits in signal transduction. Biochem Soc Trans. 1995;23141- 148
Myung  CYasuda  HLiu  WWHarden  TKGarrison  JC Role of isoprenoid lipids on the heterotrimeric G protein K subunit in determining effector activation. J Biol Chem. 1999;27416595- 16603
Link to Article
Muller  SHekman  MLohse  MJ Specific enhancement of β adrenergic receptor kinase activity by defined β and K subunits. Proc Natl Acad Sci U S A. 1993;9010439- 10443
Link to Article
Lee  CMurakami  TSimonds  WF Identification of a discrete region of the G protein K subunit conferring selectivity in β K complex formation. J Biol Chem. 1995;2708779- 8784
Link to Article
Bos  JL ras oncogenes in human cancer. Cancer Res. 1989;494682- 4689
Symons  M The Rac and Rho pathways as a source of drug targets for Ras-mediated malignancies. Curr Opin Biotechnol. 1995;6668- 674
Link to Article
Boivin  DBilodeau  DBeliveau  R Regulation of cytoskeletal functions by Rho small GTP-binding proteins in normal and cancer cells. Can J Physiol Pharmacol. 1996;74801- 810
Link to Article
Vallar  L Oncogenic role of heterotrimeric G proteins. Cancer Surv. 1996;27325- 338
Cali  JJBalcueva  EARybalkin  IRobishaw  JD Selective tissue distribution of G protein K subunits, including a new form of the K subunits identified by cDNA cloning. J Biol Chem. 1992;26724023- 24027
Ray  KKunsch  CBonner  LMRobishaw  JD Isolation of cDNA clones encoding eight different human G protein K subunits, including three novel forms designated K4, K10, K11 subunits. J Biol Chem. 1995;27021765- 21771
Link to Article
Nagorney  DMDonohue  JHFarnell  MBSchleck  CDIlstrup  DM Outcomes after curative resections of cholangiocarcinoma. Arch Surg. 1993;128871- 879
Link to Article
Nozaki  YYamamoto  MIkai  I  et al.  Reconsideration of the lymph node metastasis pattern (N factor) from intrahepatic cholangiocarcinoma using the international union against cancer TNM staging system for primary liver carcinoma. Cancer. 1998;831923- 1929
Link to Article
Mori  MMimori  KInoue  H  et al.  Detection of cancer micrometastasis in lymph nodes by reverse transcriptase-polymerase chain reaction. Cancer Res. 1995;553417- 3420
Mori  MMimori  KShiraishi  T  et al.  p27 expression and gastric carcinoma. Nat Med. 1997;3593- 594
Link to Article
Liver Cancer Study Group of Japan, General Rules for the Clinical and Pathological Study of Primary Liver Cancer. 3rd ed. Tokyo, Japan Kanehara Co Ltd1992;5- 76
Landis  CAMasters  SBSpada  APace  AMBourne  HRVallar  L GTPase inhibiting mutations activate the chain of Gs and stimulate adenylyl cyclase in human pituitary tumors. Nature. 1989;340692- 696
Link to Article
Lyons  JLandis  CAHarsh  G  et al.  Two G protein oncogenes in human endocrine tumors. Science. 1990;249655- 659
Link to Article
O'Sullivan  CBarton  CMStaddon  SLBrown  CLLemoine  NR Activating point mutations of the gsp oncogene in human thyroid adenomas. Mol Carcinog. 1991;4345- 349
Link to Article
Durand  BGao  FRaff  M Accumulation of the cyclin-dependent kinase inhibitor p27/Kip1 and the timing of oligodendrocyte differentiation. EMBO J. 1997;16306- 317
Link to Article
Lloyd  RVErickson  LAJin  L  et al.  p27kip1: a multifunctional cyclin-dependent kinase inhibitor with prognostic significance in human cancers. Am J Pathol. 1999;154313- 323
Link to Article
Morishita  RShinohara  HUeda  HKato  KAsano  T High expression of the 5 isoform of G protein in neuroepithelial cells and its replacement of the 2 isoform during neuronal differentiation in the rat brain. J Neurochem. 1999;732369- 2374
Link to Article

Figures

Place holder to copy figure label and caption
Figure 1.

Reverse transcription polymerase chain reaction of G protein γ7 (G-γ7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in 5 representative patients. Expression of G-γ7 was suppressed in the tumor tissues. The evaluated tumor-nontumor ratios of G-γ7 messenger RNA, which were corrected for the tumor-nontumor ratios of GAPDH messenger RNA, were 0.56, 0.30, 0.20, 0.29, and 0.22 in lanes 1 through 5, respectively. M indicates marker; T, tumor tissue; and N, nontumor tissue.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Expression of G protein γ7 (G-γ7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in 1 tumor tissue (lane 1), 1 nontumor tissue (lane 2), and 3 bile duct cancer cell lines (lane 3, HuCC-T1; lane 4, TFK-1; and lane 5, HuH28). None of the 3 bile duct cancer cell lines expressed the amplified DNA. M indicates marker.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Immunohistochemical staining for G protein γ7 in moderately differentiated (A) and poorly differentiated (B) intrahepatic cholangiocarcinoma. T indicates tumor tissue; N, nontumor tissue.

Graphic Jump Location

Tables

Table Graphic Jump LocationTable 1. G Protein γ7 Gene Expression and the Histological Grade of Intrahepatic Cholangiocarcinoma*
Table Graphic Jump LocationTable 2. G Protein γ7 Gene Expression and the Clinicopathological Features of 18 Patients With Intrahepatic Cholangiocarcinoma*

References

Mori  MStaniunas  RJBarnard  GFJessup  JMSteele  GD  JrChen  LB The significance of carbonic anhydrase expression in human colorectal cancer. Gastroenterology. 1993;105820- 826
Mori  MBarnard  GFStaniunas  RJJessup  JMSteele  GD  JrChen  LB Prothymosin-α mRNA expression correlates with that of c-myc in human colon cancer. Oncogene. 1993;82821- 2826
Shiraishi  TMori  MTanaka  SSugimachi  KAkiyoshi  T Identification of cystatin B in human esophageal carcinoma, using differential displays in which the gene expression is related to lymph-node metastasis. Int J Cancer. 1998;79175- 178
Link to Article
Shibata  KMori  MTanaka  SKitano  SAkiyoshi  T Identification and cloning of human G-protein K7, down-regulated in pancreatic cancer. Biochem Biophys Res Commun. 1998;246205- 209
Link to Article
Shibata  KTanaka  SShiraishi  TKitano  SMori  M G-protein K7 is down-regulated in cancers and associated with p27kip1-induced growth arrest. Cancer Res. 1999;591096- 1101
Rens  DSHamm  HE Structural and functional relationships of heterotrimeric G-proteins. FASEB J. 1995;91059- 1066
Nurnberg  BAhnert  HG Potential roles of heterotrimeric G proteins of the endomembrane systems. FEBS Lett. 1996;38961- 65
Link to Article
Wess  J G-protein–coupled receptors: molecular mechanisms involved in receptor activation and selectivity of G-protein recognition. FASEB J. 1997;11346- 354
Clapham  DENeer  EJ New roles for G-protein β K-dimers in transmembrane signaling. Nature (Lond). 1993;365403- 406
Link to Article
Muller  SLohse  MJ The role of G-protein β K subunits in signal transduction. Biochem Soc Trans. 1995;23141- 148
Myung  CYasuda  HLiu  WWHarden  TKGarrison  JC Role of isoprenoid lipids on the heterotrimeric G protein K subunit in determining effector activation. J Biol Chem. 1999;27416595- 16603
Link to Article
Muller  SHekman  MLohse  MJ Specific enhancement of β adrenergic receptor kinase activity by defined β and K subunits. Proc Natl Acad Sci U S A. 1993;9010439- 10443
Link to Article
Lee  CMurakami  TSimonds  WF Identification of a discrete region of the G protein K subunit conferring selectivity in β K complex formation. J Biol Chem. 1995;2708779- 8784
Link to Article
Bos  JL ras oncogenes in human cancer. Cancer Res. 1989;494682- 4689
Symons  M The Rac and Rho pathways as a source of drug targets for Ras-mediated malignancies. Curr Opin Biotechnol. 1995;6668- 674
Link to Article
Boivin  DBilodeau  DBeliveau  R Regulation of cytoskeletal functions by Rho small GTP-binding proteins in normal and cancer cells. Can J Physiol Pharmacol. 1996;74801- 810
Link to Article
Vallar  L Oncogenic role of heterotrimeric G proteins. Cancer Surv. 1996;27325- 338
Cali  JJBalcueva  EARybalkin  IRobishaw  JD Selective tissue distribution of G protein K subunits, including a new form of the K subunits identified by cDNA cloning. J Biol Chem. 1992;26724023- 24027
Ray  KKunsch  CBonner  LMRobishaw  JD Isolation of cDNA clones encoding eight different human G protein K subunits, including three novel forms designated K4, K10, K11 subunits. J Biol Chem. 1995;27021765- 21771
Link to Article
Nagorney  DMDonohue  JHFarnell  MBSchleck  CDIlstrup  DM Outcomes after curative resections of cholangiocarcinoma. Arch Surg. 1993;128871- 879
Link to Article
Nozaki  YYamamoto  MIkai  I  et al.  Reconsideration of the lymph node metastasis pattern (N factor) from intrahepatic cholangiocarcinoma using the international union against cancer TNM staging system for primary liver carcinoma. Cancer. 1998;831923- 1929
Link to Article
Mori  MMimori  KInoue  H  et al.  Detection of cancer micrometastasis in lymph nodes by reverse transcriptase-polymerase chain reaction. Cancer Res. 1995;553417- 3420
Mori  MMimori  KShiraishi  T  et al.  p27 expression and gastric carcinoma. Nat Med. 1997;3593- 594
Link to Article
Liver Cancer Study Group of Japan, General Rules for the Clinical and Pathological Study of Primary Liver Cancer. 3rd ed. Tokyo, Japan Kanehara Co Ltd1992;5- 76
Landis  CAMasters  SBSpada  APace  AMBourne  HRVallar  L GTPase inhibiting mutations activate the chain of Gs and stimulate adenylyl cyclase in human pituitary tumors. Nature. 1989;340692- 696
Link to Article
Lyons  JLandis  CAHarsh  G  et al.  Two G protein oncogenes in human endocrine tumors. Science. 1990;249655- 659
Link to Article
O'Sullivan  CBarton  CMStaddon  SLBrown  CLLemoine  NR Activating point mutations of the gsp oncogene in human thyroid adenomas. Mol Carcinog. 1991;4345- 349
Link to Article
Durand  BGao  FRaff  M Accumulation of the cyclin-dependent kinase inhibitor p27/Kip1 and the timing of oligodendrocyte differentiation. EMBO J. 1997;16306- 317
Link to Article
Lloyd  RVErickson  LAJin  L  et al.  p27kip1: a multifunctional cyclin-dependent kinase inhibitor with prognostic significance in human cancers. Am J Pathol. 1999;154313- 323
Link to Article
Morishita  RShinohara  HUeda  HKato  KAsano  T High expression of the 5 isoform of G protein in neuroepithelial cells and its replacement of the 2 isoform during neuronal differentiation in the rat brain. J Neurochem. 1999;732369- 2374
Link to Article

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