Measurement of MDRl Gene Expression by Real-Time
Quantitative RT-PCR Using the LightCycier Instrument
CHUNG-CHE CHANG*, SHERRIE PERKINS, CARL WITTWER
Introduction
Multidrug resistance protein (P-glycoprotein) is a 170-kDa membrane glycoprotein encoded by the MDRl gene. P-glycoprotein (P-gp) is believed to function as
an ATP-dependent efflux pump for various toxins [1,2].
P-gp has been found to be expressed at significant levels in the following
normal tissues: the biliary canaliculi of liver, the proximal tubules of kidneys,
small intestine, colon, and adrenal cortex. The expression of P-gp in these tissues has been believed to be one of the natural defense mechanisms that prevent cell damage from various toxins that these tissues may encounter. P-gp is
also expressed in endothelial cells of the CNS, testes, and placenta and this type
of expression is thought to contribute to blood-brain, blood-testicular, and
blood-placental barriers. Some subsets of hematolymphoid cells also express
P-gp, including bone marrow stem cells, lymphocytes, NK cells, and activated
macrophages [1].
Overexpression of MDRl in cancer cells can cause cross-resistance to structurally unrelated categories of chemotherapeutic agents, known as multidrug
resistance. MDRl expression in malignancies has the following patterns [1,2].
First, some types of tumors commonly express high levels of MDRl at diagnosis.
These cancers usually arise from tissues that normally express MDR1, such as
colon, kidney, adrenal, pancreas, and liver cancer. Second, some types of tumors
sometimes express high levels of MDRl at diagnosis but this is not common.
These tumors include leukemias, lymphomas, chronic myelogenous leukemia in
blast crisis, pediatric sarcomas, and neuroblastoma. Third, some types of tumors
usually express low levels of MDRl or negative expression of MDRl at diagnosis.
This group includes many chemotherapy-sensitive tumors such as untreated
breast and ovarian cancer and small-cell lung cancers. Finally, in some tumors,
including some breast and ovarian cancers, leukemias, lymphomas, and neuroblastoma, elevated MDRl expression is seen or acquired at relapse or recurrence.
This has been thought to be due to either a selective process by chemotherapy or
tumor progression independent of chemotherapy. MDRl gene promoter is a target for the c-Ha-RAS oncogene and the P53 tumor suppressor gene. Mutant P53
* Chung-Che Chang (~) (e-mail: jeffchang@pol.net)
Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
Quantitative RT-PCR Using the LightCycier Instrument
CHUNG-CHE CHANG*, SHERRIE PERKINS, CARL WITTWER
Introduction
Multidrug resistance protein (P-glycoprotein) is a 170-kDa membrane glycoprotein encoded by the MDRl gene. P-glycoprotein (P-gp) is believed to function as
an ATP-dependent efflux pump for various toxins [1,2].
P-gp has been found to be expressed at significant levels in the following
normal tissues: the biliary canaliculi of liver, the proximal tubules of kidneys,
small intestine, colon, and adrenal cortex. The expression of P-gp in these tissues has been believed to be one of the natural defense mechanisms that prevent cell damage from various toxins that these tissues may encounter. P-gp is
also expressed in endothelial cells of the CNS, testes, and placenta and this type
of expression is thought to contribute to blood-brain, blood-testicular, and
blood-placental barriers. Some subsets of hematolymphoid cells also express
P-gp, including bone marrow stem cells, lymphocytes, NK cells, and activated
macrophages [1].
Overexpression of MDRl in cancer cells can cause cross-resistance to structurally unrelated categories of chemotherapeutic agents, known as multidrug
resistance. MDRl expression in malignancies has the following patterns [1,2].
First, some types of tumors commonly express high levels of MDRl at diagnosis.
These cancers usually arise from tissues that normally express MDR1, such as
colon, kidney, adrenal, pancreas, and liver cancer. Second, some types of tumors
sometimes express high levels of MDRl at diagnosis but this is not common.
These tumors include leukemias, lymphomas, chronic myelogenous leukemia in
blast crisis, pediatric sarcomas, and neuroblastoma. Third, some types of tumors
usually express low levels of MDRl or negative expression of MDRl at diagnosis.
This group includes many chemotherapy-sensitive tumors such as untreated
breast and ovarian cancer and small-cell lung cancers. Finally, in some tumors,
including some breast and ovarian cancers, leukemias, lymphomas, and neuroblastoma, elevated MDRl expression is seen or acquired at relapse or recurrence.
This has been thought to be due to either a selective process by chemotherapy or
tumor progression independent of chemotherapy. MDRl gene promoter is a target for the c-Ha-RAS oncogene and the P53 tumor suppressor gene. Mutant P53
* Chung-Che Chang (~) (e-mail: jeffchang@pol.net)
Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226, USA