Arnold D. Rubin

The Delayed Response of Chronic Lymphocytic Leukemia Lymphocytes to Phytohemagglutinin in Vitro

Summary The kinetics of RNA, DNA, and protein synthesis were analyzed in normal and CLL lymphocytes stimulated by PHA in vitro. Normal cultures exhibited maximal increases in lymphocyte nucleic acid and protein synthesis 2 to 3 days after exposure to PHA. Under identical conditions the maximal response on the part of the lymphocytes in CLL cultures occurred between 5 to 7 days. The data suggest that many CLL lymphocytes are capable of responding to PHA but the response is distinctly delayed.

THE LYMPHOCYTES OF CHRONIC LYMPHOCYTIC LEUKEMIA: THEIR PROLIFERATION AND CELL CYCLE KINETICS

Lymphocytes obtained from CLL patients exhibited a delayed and reduced response to PHA when cultured in diffusion chambers. DNA synthesis (8–10 hr) and general time (15–19 hr) of the late‐developing CLL blasts were consistent with normal values (Ts: 8–10 hr; Tc: 14–17 hr). However, the G2 period of CLL blasts seemed more variable, and their mitotic index during the response at 5–6 days was 30–50% of the values determined for normal blasts during their peak response at 2–3 days.

Nuclear Factor-κB Modulation in Patients Undergoing Induction Chemotherapy for Acute Myelogenous Leukemia

Purpose: Nuclear factor-κB (NF-κB) is constitutively expressed in many acute myelogenous leukemia (AML) cells and AML stem cells. Ex vivo treatment of AML cells with inhibitors of NF-κB results in diminished AML cell survival and enhances the cytotoxic effects of chemotherapeutic agents. The purpose of this study was to determine if standard anti-inflammatory agents modulate AML cell nuclear NF-κB when administered in conjunction with induction chemotherapy. Experimental Design: Patients with newly diagnosed AML were treated with dexamethasone, choline magnesium trisalicylate, or both for 24 hours prior to and 24 hours following initiation of standard induction chemotherapy. AML cell nuclear NF-κB was measured at baseline, 24, and 48 hours. Results: Choline magnesium trisalicylate ± dexamethasone decreased nuclear NF-κB, whereas dexamethasone alone was associated with an increase in nuclear NF-κB in AML cells. Conclusions: These results show the feasibility of NF-κB modulation in conjunction with induction chemotherapy for patients with AML using inexpensive readily available medications. A follow-up study to determine the effects of NF-κB modulation on clinical end points is warranted.

Direct activation of DNA template in lymphocyte nuclei treated with phytohemagglutinin

Abstract Nuclei from resting lymphocytes were isolated in apparently pure and undegraded form. When exposed to phytohemagglutinin for one hour the rate of DNA directed RNA synthesis in these media doubled. Furthermore, PHA treatment of resting nuclei also resulted in increased actinomycin D binding suggesting the liberation of additional segments of free chromatin. A parallel PHA-induced increase in the incorporation of 14 C acetate (independent of protein synthesis) into acid insoluble nuclear products suggested a simultaneous augmentation in histone acetylation. These data demonstrate a direct stimulatory effect of PHA on the nuclei of resting lymphocytes.

Autoradiographic Studies of Human Lymphocytes Cultured in Vivo

Summary Human lymphocytes were cultured in diffusion chambers implanted into the peritoneal cavities of rats. In cultures treated with PHA, the pattern of morphologic transformation and initiation of DNA synthesis paralleled closely similar studies made in vitro. Immunologic stimulation of the human cells by the heterologous host was presumably minimal or absent since control cultures (without PHA) showed no significant degree of blastogenesis when compared with PHA-treated cultures. Minimum DNA synthesis time determined for the PHA-stimulated lymphocytes was 9–10 hr. Values found for the duration of Tc (16–18 hr) and minimum TG2 (2 hr) were shorter than those reported for similar studies in vitro. The in vivo culture method using Millipore chambers appears to offer a more physiologic method for studying lymphocytes.

Synthesis and processing of nuclear RNA in human monocytes after phagocytosis of polystyrene particles

Abstract Nuclear RNA was extracted from human monocytes separated by bovine serum albumin gradients. Sedimentation profiles yielded patterns of undegraded RNA. The turnover of nascent RNA in resting cells appeared to be slow. In monocytes engulfing latex particles an increase in the synthesis of 45-S rRNA precursor and an accelerated processing into mature 28-S and 18-S moieties occurred. Chase experiments indicated a higher rate of delivery of mature ribosomal RNA to the cytoplasm in these activated cells.

Control of Lymphocyte Growth in Response to Phytohemgglutinin Stimulation

Circulating lymphocytes under appropriate stimulation transform into large proliferating blast cells in a predictable fashion. When compared to resting lymphocytes, the proliferating blast cells can be distinguished morphologically by their large size, open, finely textured nuclear chromatin, prominent nucleoli and copious cytoplasm abounding with ribosomes clusters (l). These characteristics reflect heightened metabolic activities such as increased RNA and protein synthesis (2). We have previously demonstrated that phytohemagglutinin (PHA) induced enlargement of resting lymphocytes into proliferating blast cells is accompanied by an early increase in the synthesis and utilization of ribosomal RNA (rRNA) (3). Presumably this new rRNA provides for the delivery of additional cytoplasmic ribosomes and secondarily increased protein synthesis which ultimately culminates in lymphocyte growth and the morphologic appearance of a blast.

Lymphoproliferative Disorders: Recent Concepts and Implications for Therapy

The treatment of chronic lymphocytic leukemia (CLL), lymphoma and Hodgkin’s disease has been the subject of several recent detailed treatises (1–3). These relatively optimistic reports describe a variety of effective new chemotherapeutic agents and emphasize a concept that radiotherapy can potentially cure some forms of lymphoma (4–6). Furthermore, intelligent administration of therapeutic modalities has been facilitated by the introduction of additional diagnostic techniques, such as lymphangiography, which aid in the precise localization of lymphoid tumors. Finally, re-evaluation of the histologic classification of various forms of lymphomas had led to a more clear understanding of natural history and of how the course of the disease might be altered by specific therapy (7). Although empirical in nature, the information derived from these studies has been extremely helpful to the clinician. Meanwhile, recent advances in basic immunobiology, focussing on the lymphoid system as a functional unit, have uncovered some important facts regarding the biological significance of lymphoid cell proliferation. Most likely, decisive therapy of lymphoproliferative disorders will ultimately depend on the application of basic knowledge of lymphoid physiology. The present report will attempt to utilize our present knowledge of the functioning lymphoid system in a search for possible sources of malfunction and their therapeutic implications.