Cyclin D1 and p16^INK4A are preferentially expressed in immature and mature myeloma cells, respectively

Abstract

Summary. Myeloma cells consist of immature, intermediate and mature cells with respect to expression of VLA-5 (CD49e) and MPC-1 adhesion molecules. VLA-5 ¹ MPC-1 ¹ immature myeloma cells respond to interleukin 6 (IL-6) to proliferate in vitro, but VLA-5 þ MPC-1 þ mature myeloma cells have almost no proliferative activity with higher secretory activity of M-protein in vitro. In order to further clarify the biological differences between these immature and mature myeloma cells, we examined survival of these cells with or without IL-6 in vitro, and investigated the underlying mechanism of the proliferative or non-proliferative character of these cells by examining expression of cell cycle regulators such as cyclin D1 and inhibitors for cyclin-dependent kinase (Cdk), p16 INK4A , p21 CIP1 and p27 KIP1 by RT-PCR and immunohistochemistry. In vitro survival of these myeloma cells was examined by flow cytometric quantification of fluorescein diacetate (FDA) and propidium iodide (PI) staining. Immature myeloma cells rapidly entered apoptosis without IL-6, but mature myeloma cells could survive without IL-6 as well as normal mature plasma cells. Immature myeloma cells as well as myeloma cell lines expressed cyclin D1 mRNA and protein, but not any Cdk inhibitors. On the other hand, mature myeloma cells did not express cyclin D1 but expressed p16, not p21 or p27, as well as normal mature plasma cells. Therefore these results show that immature myeloma cells constitutively express cyclin D1 and can proliferate, and mature myeloma cells as well as normal mature plasma cells preferentially express p16 and can survive for a long time without proliferation.

Comparative analysis of apoptosis in HL60 detected by annexin-V and fluorescein-diacetate

“…Different from the early response, mature apoptoses seem more likely to have stopped their FDA metabolism. The result is an improved cluster differentiation, which has similarly been shown for FDA-stained lymphoblastoid (12) and mature plasma (28) cells. The advanced stage of apoptoses in these cases was confirmed by our observation of their reduced capability to exclude trypan blue.…”

Plasmablastic lymphomas and plasmablastic plasma cell myelomas have nearly identical immunophenotypic profiles

“…Unlike well-differentiated plasma cell neoplasms, plasmablastic plasma cell myelomas usually have an extremely high proliferation index and alterations in cell cycle regulators such as p16, p21, and p53. 10,[36][37][38] In situ hybridization assays for EBER were positive in all five cases of plasmablastic lymphoma analyzed, and were negative in all plasmablastic plasma cell myelomas. Although the number of cases analyzed is relatively small, the difference in EBER expression between plasmablastic lymphoma and plasma cell myeloma was highly statistically significant (Po0.002).…”

Receptor synergy of interleukin-6 (IL-6) and insulin-like growth factor-I in myeloma cells that highly express IL-6 receptor α

“…39 These sorted myeloma cells were cultured in RPMI1640 medium (Nissui, Tokyo, Japan) supplemented with 10% fetal bovine serum (FBS; M. A. Bioproducts, Walkersville, MD) with a cell-culture insert well (1.0-m pore size; Becton Dickinson, Franklin Lakes, NJ) at 37°C with 5% CO 2 . All samples were obtained from the patients with appropriate informed consent.…”