Dennis W. Ross

Epstein-Barr Virus Integration in Human Lymphomas and Lymphoid Cell Lines

Background. Epstein‐Barr virus (EBV) is maintained as an episome in most infected cells. The presence of fused terminal restriction enzyme fragments distinguishes the circular DNA form from the linear virion form.

Differentiation versus cytoreduction during remission induction in acute nonlymphoblastic leukemia treated with sequential high‐dose ara‐C and asparaginase

Patients with acute nonlymphoblastic leukemia (ANLL) treated with sequential high‐dose ara‐C and asparaginase (HiDAC → ASNase) have occasionally exhibited an unusual morphologic picture during induction therapy with a transition period in which large numbers of blasts coexist with returning mature hemopoietic elements. In 2 of 11 adult patients with ANLL treated during a 6‐month period using a new protocol of HiDAC → ASNase, the hypoplastic phase typically seen after intense induction never developed. Serial marrow examinations performed 7 to 35 days after treatment showed equal admixtures of blasts and mature elements. Despite these findings, both patients subsequently entered complete remission with morphologically normal bone marrow examinations. The possibility for diagnostic error in interpreting these transition marrows as failed inductions is great and could lead to cessation of supportive therapy or to an unnecessary further course of cytotoxic therapy. This phenomenon raises the biological question, does remission represent leukemia killed or leukemia matured?

A proposed staging system for chronic myeloid leukemia

A staging system was proposed for chronic myeloid leukemia (CML) that groups patients into three stages (I, II, and III), each with two subclasses (A and B). The system uses pathologic parameters, of which the percentage of blasts in the blood and bone marrow is the most important. CML is defined as a myeloproliferative disorder with molecular or cytogenetic evidence of the translocation of the abl oncogene on chromosome 9 to the breakpoint cluster region gene on chromosome 22. The proposed staging system is similar in format to the standard TNM system used for many solid tumors.

Viscous factors in peripheral tissue perfusion.

To ascertain the relative importance of the factors that influence blood viscosity (VIS), we measured hematocrit (HCT), filterability index, fibrinogen level (FIB), and Ektacytometer indices at osmolarities of both 290 (EI 290) and 200 (EI 200) in 21 diabetic patients with peripheral vascular disease (DPVDs) and 11 healthy volunteers (HVs). Stepwise multiple regression analyses generated a formula based on three of the independent variables (FIB, HCT, EI 200) that accurately predicted VIS (r = 0.79, p less than 0.01). Based on the beta coefficients and F statistics, HCT and FIB were the most important elements in the linear regression equation. Compared with HVs the total group of DPVDs had lower HCT (36.5% vs. 42.4%) and higher FIB (661 vs. 276 mg/dl, p less than 0.01) values. When all HVs were compared with a subgroup of DPVDs with similar HCT (n = 10), both FIB and VIS were higher (p less than 0.001) in the DPVD than in the HV group. We conclude that the most important of the multiple factors that influence VIS are HCT and FIB. The finding of increased FIB in DPVDs could have important implications for drug and surgical therapy in this group of patients.

The nature of unbalanced cell growth caused by cytotoxic agents

SummaryThe volume of cells grown in tissue culture following exposure to a wide variety of cytotoxic drugs or x-rays increases at a rate of 1 to 10% of cell mass per hour. The same phenomenon is seen in animal neoplasias and human leukemias. This increase in cell volume is the result of unbalanced cell growth with a resulting disproportionate synthesis of proteins and possibly other macromolecules in the cytoplasm and nucleus. The dose response curve for a decrease in cell survival as measured by cloning efficiency in tissue culture is quantitatively correlated with the dose response curve for inducing an increase in cell volume. This quantitative relationship makes feasible the use of the phenomenon of unbalanced cell growth as a measure of cell death in screening for cytotoxic drugs or in monitoring response to therapy. An hypothesis to explain this increase in cell volume following chemotherapy is that cells are by the action of these drugs induced into an abortive or unbalanced pseudo-cycle which is characterized by synthesis of substantial amounts of protein without other preparative steps for cell division.

Flow cytometric correlation of the c-myc oncoprotein and cell cycle kinetics of HL60 leukaemia during induced maturation with cytosine arabinoside and dimethylsulphoxide

Abstract The c‐myc oncogene codes for a DNA binding protein that functions in a cell cycle‐related manner. A useful model for studying the relationship of c‐myc expression with cell cycle kinetics is the HL60 cell line. HL60 cells constitutively express high levels of c‐myc mRNA; however, the level can be down‐regulated as the cells are induced to differentiate. We have developed a flow cytometric assay for correlating c‐myc oncoprotein levels with DNA content. C‐myc oncoprotein levels were additionally correlated with c‐myc mRNA levels as determined by slot blot hybridization. Dimethylsulphoxide (DMSO) and cytosine arabinoside were used to induce granulocytic and monocytic maturation respectively. Treatment of HL60 cells with DMSO leads to an increase in the per cent of cells in G1/G0 and a decrease in mean c‐myc mRNA and oncoprotein levels. The cells with G1 DNA content show the greatest decrease in c‐myc protein. ARA‐c treatment of HL60 cells leads to a slowing and an accumulation of cells in S phase with a moderate decrease in mean mRNA and only a slight decrease in mean c‐myc protein levels. These data support the hypothesis that c‐myc is involved in the switch from G1 to G0.

Cancer: The Emerging Molecular Biology

Discoveries at the molecular level have greatly increased our understanding of how a normal cell becomes a tumor cell, responsive only to growth signals. Cancer emerges as fundamentally genetic, representing mutations in protooncogenes and tumor suppressor genes arising from multiple “hits” over long spans of time. The knowledge portends abilities to interrupt the process at a precancerous stage.

Gene Regulation and Expression

A gene is a segment of DNA consisting of codons specifying the amino acids for a protein and of control sequences which regulate gene expression. When a cell divides, the entire human genome, that is, all the DNA stored within the nucleus, must be copied. In Figure 2.1 the replication of DNA is demonstrated. The regulation of a cell’s function is controlled by altering gene expression. The steps in gene expression are (1) transcription of the gene’s DNA to RNA, (2) RNA processing to produce a spliced mRNA, (3) translation of mRNA on a polyribosome to a polypeptide chain, and (4) final protein processing to the functional tertiary form. Figures 2.2 through 2.5 illustrate the steps in this process, which will be covered in more detail later in this chapter.

Cl - Permeabilities in Red Blood Cells and Peripheral Blood Lymphocytes from Cystic Fibrosis and Control Subjects

ABSTRACT: Recent studies have identified abnormalities in Cl- permeation across two target cystic fibrosis (CF) epithelia (sweat duct and respiratory epithelium). In the present study, anion conductances of red blood cells (RBCs) and peripheral blood lymphocytes (PBLs) from CF and normal subjects were estimated and compared. For RBCs, the valinpmycin-induced rate constant for K+ loss (PK+) was taken as an index of PCl- For PBLs, the secondary volume increase after gramicidin pretreatment and hypotonic (0.67 × isotonic) stress was used to estimate PCl- The CI- permeabilities of RBCs and PBLs from CF and control subjects were comparable. These findings suggest that the abnormality in PCl- reported for CF sweat ductal and respiratory epithelia is not expressed in circulating blood elements.

Volume increase in L5222 leukemic cells following chemotherapy: manifestation of leukemic cell damage.

Abstract The L5222 leukemia of the BDIX rat provides an important model for the study of the effects of chemotherapy on leukemic cell proliferation. In this model system, damage done to leukemic cells by chemotherapeutic agents manifests itself as an increase in cell volume within a few hours following exposure. This effect is seen in vivo following intraperitoneal injection of drug or in vitro if the leukemic cells are removed and exposed to drug in short-term culture. The normal mature peripheral white blood cells of the animal when measured separately do not show this volume increase reflecting cell damage. The method of measuring cell volume as a means of assessing damage to leukemic cells and the lack of such an effect in normal blood cells is a means of more closely monitoring chemotherapeutic drug schedules. The mechanism producing this volume effect in leukemic cells but not in normal mature cells remains to be elucidated.