Abstract

Effects of Krüppel-like Factor ₄ Overexpression on Cell Growth Rate, Cell Cycle, Cell Differentiation, and Apoptosis in Acute Myeloid Leukemia Cell Lines

Student: Xi Peng
Mentor: Daniel Lacorazza (Baylor College of Medicine and Texas Children’s Hospital)

Acute myeloid leukemia (AML) is a malignant disease of the bone marrow, in which the bone marrow starts to make blasts that have not completely matured. The mechanism of the developmental arrest in AML is under study, but previous studies have shown that the expression of Krüppel-like factor ₄, a transcription factor, is repressed in AML cell lines and patient samples. We are studying whether overexpressing KLF₄ has any effects on cell growth rate, cell cycle, cell differentiation, and apoptosis in the AML cell lines that previously do not have KLF₄ expression. Understanding the role of KLF₄ in AML will lead to a better understanding of the disease on the molecular level, and may lead to more effective treatments. 

Acute myeloid leukemia (AML) is a malignant disease of the bone marrow, in which hematopoietic precursors are arrested in an early stage of development. The mechanism of the developmental arrest in AML is unclear, but previous studies have shown that the Krüppel-like factor ₄ (KLF₄), a transcription factor that regulates proliferation, differentiation, apoptosis and somatic cell reprogramming, is repressed in AML cell lines and patient samples. The restoration of expression is expected to inhibit cell growth and promote differentiation. The hypothesis is that KLF₄ acts as a tumor suppressor in AML by regulating monocyte differentiation and cell cycle progression. KLF₄ overexpression in two AML cell lines (NB-₄ and MM6) was induced via retroviral transduction with the retroviral supernatant produced by calcium phosphate transfection of 293T cells. The NB-₄ or the MM6 cells were transduced with either the empty vector MIGR1 (LTR-iRES-GFP-LTR), or MIGR1-KLF₄ (LTR-KLF₄-iRES-GFP-LTR). The transduced NB-₄ cells were sorted using the flow cytometer, and the live cells with high GFP+ expression were collected for cell growth rate monitoring, cell cycle analysis, Annexin V apoptosis detection, and cell differentiation analysis via surface markers detection (CD1₄, CD16, CCR2, CD33, and CD66b). The results suggested that KLF₄ overexpression repressed the cell growth rate significantly, increased the cell population in the SubG1 phase, and decreased the cell population in the S phase in the NB-₄ cell line. The surface markers detection showed that KLF₄ overexpression increased CD1₄ expression in both cell lines suggesting differentiation, and resulted in a significant larger apoptotic population in the NB-₄ cell line. The observations suggested that KLF₄ overexpression could contributes to the cell cycle arrest and apoptosis in AML cell lines, which was consistent with the initial hypothesis.