ACTIVATION AND EXPRESSION OF CELLULAR ONCOGENES AND ONCOGENIC VIRUSES IN HUMAN TUMORS
Main researcher
: SORIĆ, JASNA (44124) Assistants
KRUŠIĆ, JOSIP (24155)
RUDAN, NIKOLA (41652)
BRDAR, BRANKO (5323)
BAN, JASNA (1894)
ŠARČEVIĆ, BOŽENA (87995)
MATULIĆ, MAJA (188920)
BANJAC-CEROVAC, ŽELJKA (900549)
LONČAREK, JADRANKA (900831)
Type of research: basic Duration from: 01/01/91. to 12/31/95. Papers on project (total): 34
Papers on project quoted in Current Contents: 8
Institution name: Središnji institut za tumore i slične bolesti, Zagreb (74) Department/Institute: Department of molecular genetics, Laboratory for experimental ca Address: Bijenička 54, City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 4561-093,4561-111/1678
Fax: 385 (0)425-647, 425-497
E-mail: jsoric"olimp.irb.hr
Summary: Activation and expression of cellular oncogenes and the
integration of oncogenic viruses into host cell genome, play a critical
role in the development of the malignant tumors. Increased levels of the
c-src oncogene expression have been observed in certain human tumor cell
lines and tissues. We have shown that the level of c-src oncogene product,
pp60 c-src, kinase activity in T47D cells is increased 10-20 fold over
that found in another human breast cancer cellline, MCF7, or chicken
embryo fibroblasts, despite similar protein levels in all three cells.
Normal human mammary epithelial cells do not express pp60 c-src. Recently,
interest has been focused on oncogenes and their role in the responce of
malignant cells to cancer therapy. We have shown that tiazofurin (TR)
provided synergism with difluorodeoxycytidine (DFDC). DFDC inhibited
proliferation in OVCAR-5 human ovarian carcinoma cells and colony
formation in PANC-1 human pancreatic carcinoma cells. Further, in HL-60
human leukemia cells DFDC induced differentiation and inhibited
proliferation in a dose-dependet manner. TR and DFDC provide synergistic
cytotoxycity in rat hepatoma cells and additive in PANC-1 cells. The two
drugs together should be helpful in treating leukemias and solid tumors in
humans. Multiple fractions of gamma rays (0.5Gy daily, 30 fractions) had
previously been found to change the sensitivity of human cervical
carcinoma HeLa cells to anticancer drugs. We have shown that
preirradiation did not induce either amplification or elevated expression
of c-myc or c-Ki-ras oncogenes. Further, there is no correlation between
expression of c-myc and c-Ki-ras oncogenes and the acquired resistance to
cisplatin. Also, the development of resistance of human larynx carcinoma
cells to cisplatin and vincristine does not alter the expression of c-myc
or c-Ki-ras oncogenes. We did not find any correlation between expression
of these oncogenes and the sensitivity to cisplatin, methotrexate or gamma
rays. Therefore, it is not possible to predict the response of the
malignant cells to cancer treatment solely on the basis of the presence of
activated oncogenes. In addition, we investigate the role of human
papillomaviruses (HPV), oncogenic DNA viruses, in benign and malignant
neoplasia of the uterine cervix and head and neck tumors. We have found
that HPV types 16 and 18 are mainly associated with cervical carcinoma and
are frequently detected in an integrated state with the cellular
DNA;genome types 6 and 11 were found to be in an episomal DNA form
prevailing in benign tumors. C-myc protooncogene was not rearanged or
amplified in analyzed cervical lesions. To enable routine screening of
premalignant cervical lesions for HPV DNA, we have developed a sensitive
method of detecting HPV 6, 16 and 18 in cervical scrapes using dot blot
hybridization assay. The method visualised an amount of target DNA as low
as 10pg without background. The technique is easy to do, sensitive and
specific, and may significantly contribute to the management of cervical
dysplasia. We performed the cloning and expression of human
microplasminogen (mPlg), a truncated (28kDa) form of plasminogen (Plg).
mPlg retained the characteristic properties of the parent protein as
redards activation by urokinase (uPA). The two methionine residues of
mPlg, M53 and M256, were replaced, respectively, by Q53 and L256, to yield
a methionineless protein (mPlgM-) whose catalytic properties were
indistinguishable from mPlg itself; the modified mPlgM- was not detectable
altered upon exposure to CNBr in formic acid under conditions used for
peptide chain cleavage at methionine residues. Replacement of R29 by M29
at the activation site of mPlg yielded a mutant protein resistant to
activation by uPA, but able to form an active complex with streptokinase
(SK). This mutant was activated by CNBr to a mPlg whose catalytic
properties were qualitatively identical to the reference enzyme mPlg.
Research goals: Increased levels of c-src oncogenes expression have
been observed in certain human tumor cell lines and tissues. T47D human
breast cancer cells are genetically unstable with heterogenous chromosome
amplification, including chromosome 20, site of the c-src gene. The goal of
this research is to determine the tyrosyl kinase activity of pp60 c-src,
the oncogene product of c-src gene in T47D, MCF7 human breast cancer cells
and normal human mammary epithelial cells. The HPV integration in host cell
genome might play an important role in tumorigenic process. There are some
evidence that HPV infection might be an etiological factor in the
development of human cervical cancer.The presence of specific HPV DNA in
biopsies derived from condyloma acuminatum, dysplasias and cervical
carcinoma tissues is examined. In addition to this, we are examinating if
the integration of the HPV sequences into a host cell genome can activate
the cellular oncogenes. We examine the influence of anticancer drugs and
irradiation in cell culture on differentiation, cytotoxicity and resistance
of human carcinoma cells. Multiple fractions of gamma rays ( 0.5Gy daily,
30 fractions ) had previously been found to change the sensitivity of human
cervical carcinoma HeLa cells to anticancer drugs, cisplatin, methotrexate
and vincrustine. We examine whether multiple fractions of gamma rays can
induce the amplification or over expression of c-myc and c-Ki-ras
oncogenes. Further, we examine whether the development of resistance to
cisplatin and vincristine changes the expression of c-myc and c-Ki-ras
oncogenes and to determine whether there is a correlation between the
sensitivity of selected clones to cisplatin, methotrexate and gamma rays.
COOPERATION - PROJECTS
COOPERATION - INSTITUTIONS
Name of institution
: Institut "Ruđer Bošković" Type of institution: State institute Type of cooperation: Joint project City: 10000 - Zagreb, Croatia
Name of institution
: Farmaceutsko-biokemijski fakultet Type of institution: University/Faculty Type of cooperation: Joint project City: 10000 - Zagreb, Croatia
Name of institution
: Prirodoslovno-matematički fakultet Type of institution: University/Faculty Type of cooperation: Joint project City: 10000 - Zagreb, Croatia Other information about the project.