HEL

Calothrixin B Derivatives Induce Apoptosis and Cell Cycle Arrest on HEL Cells

Acute erythroleukemia (AEL) is AML characterized by malignant erythroid proliferation. Calothrixin B is a carbazole alkaloid isolated from the cyanobacteria Calothrix and exhibits anti-cancer activity. H-107 has the most potent inhibitory effect on HEL cells, and the IC50 was 3.63 ± 0.33 μM (Table 1). H-107 inhibited HEL cell proliferation in a significant time and dose-dependent manner (Fig. 1A-C). The morphology of HEL cells treated with H-107 gradually shrank and fragmented with the time and concentrations increasing (Fig. 1D). These data suggest that H-107 effectively inhibited HEL cell growth.

Early apoptosis (annexin-V positivity) and late apoptosis (annexin-V/PI positivity) were assessed by flow cytometry. The results displayed that the apoptosis rate of HEL cells treated with H-107 (8 μM) for 48 h was 24.58 ± 0.32%, and the apoptosis rate increased to 32.11 ± 0.68% for 72 h (Fig. 2A and B). Furthermore, H-107 induced HEL cell apoptosis for a significant time and was dose-dependent. The Hoechst 33258 staining indicated that damaged DNA was detected in HEL cells treated with H-107. The result showed that the DNA damage levels were increased in a dose-dependent manner (Fig. 2C).

Fig. 1 H-107 inhibited HEL cell proliferation. (Wang B, et al., 2024)

Fig. 2 H-107 induced apoptosis in HEL cells. (Wang B, et al., 2024)

Reactivity of Anti-HEL Cell Monoclonal Antibodies With Normal Hematopoietic Cells

The characteristics of nine monoclonal antibodies (MoAbs) produced using the uninduced cells of a human erythroleukemia line (HEL) as immunogen are described. The proportion of labeled bone marrow cells varied from a very small fraction (antibody 53/10) up to 88% of the cells (antibody 52/40). Based on the frequency of labeled bone marrow cells, the antibodies were classified into four groups, A-D (Fig. 3).

Antibodies of group A (52/10, 52/40, 53/40, 54/ 16) labeled from 43% to 88% of bone marrow cells. In addition, they reacted with large proportions of granulocytes (from 43% to 76%), with 75%-95% of nonadhering non-E rosetting mononuclear cells, and with over 90% of T lymphocytes. The four antibodies failed to react with erythrocytes but did react with erythroblasts. MoAb 53/40 recognized platelets and megakaryocytes.

Antibodies of group B (53/5, 53/6) labeled 17%- 18% of bone marrow cells, a minor population of the non-adhering non-rosetting mononuclear cells, and the monocyte and the T cell fractions, but no granulocytes. The two group B MoAbs failed to react with red cells; they did recognize a small proportion of bone marrow erythroblasts, mainly the immature ones; they labeled strongly the majority of culture-derived erythroblasts.

The two antibodies of group C labeled 100% of the platelets, bone marrow megakaryocytes, and culture-derived megakaryocytic colonies. There was no labeling of red cells or erythroblasts. The antibodies labeled 4%-8% of bone marrow cells and minor populations of granulocytes, monocytes, nonadhering non-rosetting cells, and T cell fractions; whether this small reactivity was due to platelet adsorption on the surface of these cells was not determined.

Antibody 53/10 (the antibody of group D) labeled 1.3% of bone marrow cells, 3.7% of monocytes, 0.8% of non-adhering non-rosetting cells, and 3.7% of T cells. This monoclonal antibody failed to label platelets, erythrocytes, or granulocytes.

Fig. 3 Reactivity of anti-HEL cell monoclonal antibodies with normal cells (upper panel) and cells of hemopoietic cell lines (lower panel). (Papayannopoulou T, et al., 1984)