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Am J Transl Res 2013;5(1):36-46
Original Article
Cladribine and bendamustine exhibit inhibitory activity in dexame-
thasone-sensitive and -resistant multiple myeloma cells
Bo Cai, Shuiliang Wang, Jingcao Huang, Choon-Kee Lee, Chunji Gao, Bolin Liu
Department of Hematology, Chinese PLA General Hospital, Beijing, China; Department of Pathology, Department
of Medicine, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; State Key
Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, Chinese Academy
of Medical Sciences and Peking Union Medical College, Tianjin, China. *Current address: San Juan Cancer
Center, Montrose Memorial Hospital, Montrose, CO, USA.
Received December 10, 2012; Accepted January 2, 2013; Epub January 21, 2013; Published January 30, 2013
Abstract: Cladribine (2-CDA) is a well-known purine nucleoside analog with activities against lymphoproliferative
disorders such as hairy cell leukemia (HCL). Bendamustine, a hybrid molecule of purine analog and alkylator,
induces apoptosis via DNA damage response and inhibition of mitotic checkpoint. Their therapeutic potential in
patients with multiple myeloma (MM), particularly those become resistant to traditional chemotherapeutic agents,
remains unclear. Here we study the effects of cladribine or bendamustine on dexamethasone-sensitive (MM1.S)
and -resistant (MM1.R) MM cells. MTS-based proliferation assays showed that cladribine and bendamustine
exhibited similar anti-proliferation/anti-survival effects on MM1.S and MM1.R cells in a dose-dependent manner.
The IC50s of cladribine were approximately 35.3 nmol/L and 58 nmol/L for MM1.S and MM1.R cells, respectively.
The IC50s of bendamustine were approximately 119.8 μmol/L (MM1.S) and 138 μmol/L (MM1.R). An apoptotic-
ELISA and western blot assays of PARP cleavage and activation of caspase-8 and caspase-3 indicated that
cladribine or bendamustine induced apoptosis in both cell lines. Similar results were obtained with flow
cytometric analysis showing that cladribine or bendamustine increased the sub-G1 population. Treatment with
bendamustine but not cladribine also resulted in cell cycle S-phase arrest. Either cladribine or bendamustine led
to a remarkable increase of the phosphorylated H2A.X, CHK1 and CHK2 in both MM1.S and MM1.R cells,
suggesting an induction of DNA damage response. Collectively, we demonstrate that cladribine and
bendamustine exert potent inhibitory effects on dexamethasone-sensitive and -resistant MM cells in vitro. Our
data suggest that MM patients, including those with dexamethasone resistance, may particularly benefit from
cladribine or bendamustine. (AJTR1212001).
Keywords: Cladribine, bendamustine, dexamethasone resistance, DNA damage response, apoptosis, multiple
myeloma
Address correspondence to: Dr. Bolin Liu, Department of Pathology, Mail Stop-8104, School of Medicine,
University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave., Aurora, CO 80045, USA. E-mail: bolin.
liu@ucdenver.edu; Dr. Chunji Gao, Department of Hematology, Chinese PLA General Hospital, 28 Fuxing Road,
Beijing 100853, China. E-mail: gaochunji@medmail.com.cn
Original Article
Cladribine and bendamustine exhibit inhibitory activity in dexame-
thasone-sensitive and -resistant multiple myeloma cells
Bo Cai, Shuiliang Wang, Jingcao Huang, Choon-Kee Lee, Chunji Gao, Bolin Liu
Department of Hematology, Chinese PLA General Hospital, Beijing, China; Department of Pathology, Department
of Medicine, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; State Key
Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, Chinese Academy
of Medical Sciences and Peking Union Medical College, Tianjin, China. *Current address: San Juan Cancer
Center, Montrose Memorial Hospital, Montrose, CO, USA.
Received December 10, 2012; Accepted January 2, 2013; Epub January 21, 2013; Published January 30, 2013
Abstract: Cladribine (2-CDA) is a well-known purine nucleoside analog with activities against lymphoproliferative
disorders such as hairy cell leukemia (HCL). Bendamustine, a hybrid molecule of purine analog and alkylator,
induces apoptosis via DNA damage response and inhibition of mitotic checkpoint. Their therapeutic potential in
patients with multiple myeloma (MM), particularly those become resistant to traditional chemotherapeutic agents,
remains unclear. Here we study the effects of cladribine or bendamustine on dexamethasone-sensitive (MM1.S)
and -resistant (MM1.R) MM cells. MTS-based proliferation assays showed that cladribine and bendamustine
exhibited similar anti-proliferation/anti-survival effects on MM1.S and MM1.R cells in a dose-dependent manner.
The IC50s of cladribine were approximately 35.3 nmol/L and 58 nmol/L for MM1.S and MM1.R cells, respectively.
The IC50s of bendamustine were approximately 119.8 μmol/L (MM1.S) and 138 μmol/L (MM1.R). An apoptotic-
ELISA and western blot assays of PARP cleavage and activation of caspase-8 and caspase-3 indicated that
cladribine or bendamustine induced apoptosis in both cell lines. Similar results were obtained with flow
cytometric analysis showing that cladribine or bendamustine increased the sub-G1 population. Treatment with
bendamustine but not cladribine also resulted in cell cycle S-phase arrest. Either cladribine or bendamustine led
to a remarkable increase of the phosphorylated H2A.X, CHK1 and CHK2 in both MM1.S and MM1.R cells,
suggesting an induction of DNA damage response. Collectively, we demonstrate that cladribine and
bendamustine exert potent inhibitory effects on dexamethasone-sensitive and -resistant MM cells in vitro. Our
data suggest that MM patients, including those with dexamethasone resistance, may particularly benefit from
cladribine or bendamustine. (AJTR1212001).
Keywords: Cladribine, bendamustine, dexamethasone resistance, DNA damage response, apoptosis, multiple
myeloma
Address correspondence to: Dr. Bolin Liu, Department of Pathology, Mail Stop-8104, School of Medicine,
University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave., Aurora, CO 80045, USA. E-mail: bolin.
liu@ucdenver.edu; Dr. Chunji Gao, Department of Hematology, Chinese PLA General Hospital, 28 Fuxing Road,
Beijing 100853, China. E-mail: gaochunji@medmail.com.cn
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