Characterisation of Induced Rat Mammary Gland Tumor and the Antitumor Effect of Recombinant Human Erythropoietin and Tamoxifen
Breast cancer is the most common cancer and the incidence and mortality rate had remained high. In Malaysia alone, breast cancers accounted for 31% of all new cancer cases and are among the most fatal cancers. Since breast cancers are complex diseases, there is no single marker that is both sensi...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2009
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/7554/1/ABS_---__IB_2009_12.pdf |
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| Summary: | Breast cancer is the most common cancer and the incidence and mortality rate
had remained high. In Malaysia alone, breast cancers accounted for 31% of all
new cancer cases and are among the most fatal cancers. Since breast cancers
are complex diseases, there is no single marker that is both sensitive and
specific for early detection of the disease. The present study was undertaken to
characterize rat mammary gland tumors as a model for breast cancers and to
determine parameters that could be used as early tumor markers. The study
also undertook to determine the effect of recombinant human erythropoietin
(rHuEPO) and Tamoxifen on the rat mammary gland tumor.
In the first part of the study serum biochemical parameters, angiogenic factors
and tumor markers, tumor histopathology and ultrastructure and expression of
estrogen (ER) and erythropoietin receptors (EPOR) were determined. Twenty
female Sprague-Dawley rats, aged six to seven weeks were divided into two groups of 10 rats per group. The rats were treated intragastrically, the first
group with 20 mg 7,12-dimethylbenz(a)anthracene (DMBA) per rat to induce
mammary tumor development and the second group with 1 mL 0.9% normal
saline and served as the control. The animals were palpated weekly for tumor
mass and sacrificed two weeks after tumor occurrence. Blood was withdrawn
through cardiac puncture before tumor induction and weekly thereafter. Serum
biochemical parameters analysed were alkaline phosphatase (ALP), aspartate
aminotransferase (AST), alanine transferase (ALT), lactate dehydrogenase
(LDH), creatinine kinase (CK), glucose, blood urea nitrogen (BUN) and
creatinine by a chemistry analyser using standard diagnostic kits. Serum tumor
markers,namely α-fetoprotein (AFP) and CA15-3 were analysed using
automated immunoassay analyser, while the angiogenic factors, matrix
metalloproteinase-2 (MMP-2) and vascular endothelial growth factor (VEGF)
were determined by the ELISA technique. Tumor tissues excised from
sacrificed animals were subjected to histopathological analysis and ER-α and
EPOR determination through immunohistochemistry (IHC). Tumor ultrastructure
was examined by transmission electron microscopy (TEM).
The results showed higher ALT, ALP and AST concentrations in the DMBAtreated
than the control group reflecting abnormal liver function. Pronounced
increases in serum LDH were also observed in the DMBA-treated group.
Angiogenic factor estimations showed that serum MMP-2 levels remained high
throughout the study and seemed to have played a greater role than VEGF in early stage tumorigenesis. Serum tumor markers, AFP and CA 15.3 were not
detected in either the treated or control rats. Histopathological analysis showed
features typical of neoplastic cells which were enlarged nuclei, conspicuous
nucleoli nuclear pleomorphism, high nuclear to cytoplasma ratio,
hyperchromasia, and epithelial cell and stroma hyperplasia. These features are
similar to that found in breast cancers. Immunohistochemical analysis showed
that ER-α and EPOR were present in the DMBA-induced rat mammary tumor,
which also resemble human breast cancers. Transmission electron microscopy
analysis of the tumor demonstrated the co-existence of apoptosis, necrosis and
aponecrosis which may be used in the determination of mammary gland tumor
and breast cancer development in the early stages.
In conclusion, the combination of serum liver-related enzymes, serum MMP-2
and histological changes, ER-α and EPOR expression, evidences of apoptosis,
necrosis and aponecrosis may form the panel for screening and determination
of early mammary gland tumors in high risk cancer patients.
The second phase of the study involved the development of a xenograftinduced
mammary gland tumor model in rats as a substitute for the
conventional drug-induced method. The xenograft-induced mammary gland
tumor seems to be reliable and can produce tumors within a short period. The
xenograft model was then used to evaluate the effects of rHuEPO, Tamoxifen
and Tamoxifen-rHuEPO combination on mammary gland tumor growth and angiogenesis. In this study, 24 rats were divided into four groups of six rats
each. Each rat was treated orally: Group 1 with 60 IU rHuEPO; Group 2 with 20
mg Tamoxifen; Group 3 with a combination of 20 mg Tamoxifen and 60 IU
rHuEPO; Group 4 with 1 mL 0.9% normal saline and served as the control. The
results showed that rHuEPO did not promote mammary tumor growth and in
fact may enhance the cytotoxicity of Tamoxifen through the stimulation of
proapoptotic and antiproliferative effects. This study suggests that rHuEPO
treatment in cancer patients may not only be beneficial for the alleviation of
anemia due to the disease, but also augments the effect of certain
chemotherapeutic drugs used in the treatment of cancer |
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