Depression accelerates the development of gastric cancer through reactive oxygen species­activated ABL1 (Review).

Depression is a common symptom among gastric cancer (GC) patients and serves as a potential indication of poor prognosis and advanced cancer clinical stage. However, the molecular mechanism of depression­associated poor prognoses of GC patients remains unclear. Recent studies have revealed that GC patients with depression are under high levels of oxidative stress (OS) status that is accompanied by the dysfunction of numerous proto­oncogenes, including the ABL proto­oncogene 1 (ABL1), which is a non­receptor tyrosine kinase. Recent evidence indicates that ABL1 was dysregulated in both major depressive disorder (MDD) and cancer patients with depression, and high levels of reactive oxygen species (ROS) can lead to the activation of ABL1 in response to OS and that activated ABL1 subsequently contributes to development of GC via interactions with the downstream targets and corresponding signaling pathways. In this review, we examine the evidence to illuminate the molecular mechanism of ABL1 in the progression of GC patients with depression and identify out new and effective methods for the initial and long­term treatment of GC.

Importance of DNA damage in the induction of apoptosis by ionizing radiation: effect of the scid mutation and DNA ploidy on the radiosensitivity of murine lymphoid cell lines.

PURPOSE: To study the effects of the murine scid mutation and DNA ploidy on the susceptibility of lymphoid cell lines to induction of apoptosis by ionizing radiation and thereby to determine whether DNA lesions are critical initiators of apoptosis. MATERIALS AND METHODS: Sensitivity to killing and rapidity of induction of apoptosis following y-irradiation or DNA-associated 125I decays were compared in pre-B and pre-T cell lines derived from wild-type mice and from mice homozygous or heterozygous for the scid mutation. Effects of differences in DNA ploidy on the same endpoints were studied using pseudo-diploid and -tetraploid clones of a murine pre-T cell line. RESULTS: Pairs of pre-B- and pre-T cell-derived lines that expressed wild-type p53 and underwent rapid interphase apoptosis after irradiation were identified. In both cases, the scid homozygous cell lines were more sensitive to killing, suggesting that DNA repair capability influences susceptibility to induction of apoptosis. Increasing DNA ploidy in a cell line that undergoes rapid interphase apoptosis produced a corresponding increase in the number of DNA lesions required to produce a lethal event; again consistent with DNA being the target for radiation action. CONCLUSION: DNA damage is an important, if not the sole, initiator of external beam ionizing radiation-induced apoptosis.

Activated abl oncogenes and apoptosis: differing responses of transformed myeloid progenitor cell lines.

Activation of the c-abl protooncogene occurs during the generation of both the Abelson murine leukemia virus and the bcrabl fusion gene. To further dissect the biological properties of these proteins, we studied their effect on apoptosis. Using dimethyl sulfoxide (DMSO) to induce apoptosis in the murine myeloid progenitor cell line 32Dcl3, we examined the effect of expression of both v-abl and bcrabl transgenes on apoptosis. v-abl expressing 32Dcl3 cells are sensitive to apoptosis induction, similar to parental 32Dcl3 cells. In contrast, bcrabl expression 32Dcl3 cells are protected from the apoptotic stimulus resulting from DMSO exposure. Analyzing the expression patterns for Bcl-2 and Bax, two proteins known to modulate the apoptotic response, we found a downregulation of Bcl-2 and enhanced expression of Bax in 32Dcl3 cells. In 32Dcl3/v-Abl cells, Bcl-2 expression remained constant while Bax was upregulated, whereas in 32Dcl3 cells expressing bcrabl, there was continuous expression of Bcl-2 at a level greater than observed in v-abl transformed cells. Taken together, our data demonstrate that although both activated abl gene products promote overlapping effects of some biological responses (i.e., factor-independent proliferation) they diverge in their effect on apoptotic signaling pathways.

Wild-type p53 induces diverse effects in 32D cells expressing different oncogenes.

Expression of exogenous wild-type (wt) p53 in different leukemia cell lines can induce growth arrest, apoptotic cell death, or cell differentiation. The hematopoietic cell lines that have been used so far to study wt p53 functions have in common the characteristic of not expressing endogenous p53. However, the mechanisms involved in the transformation of these cells are different, and the cells are at different stages of tumor progression. It can be postulated that each type of neoplastic cell offers a particular environment in which p53 might generate different effects. To test this hypothesis, we introduced individual oncogenes into untransformed, interleukin-3 (IL-3)-dependent myeloid precursor 32D cells to have a single transforming agent at a time. The effects induced by wt p53 overexpression were subsequently evaluated in each oncogene-expressing 32D derivative. We found that in not fully transformed, v-ras-expressing 32D cells, as already shown for the parental 32D cells, overexpression of the wt p53 gene caused no phenotypic changes and no reduction of the proliferative rate as long as the cells were maintained in their normal culture conditions (presence of IL-3 and serum). An accelerated rate of apoptosis was observed after IL-3 withdrawal. In contrast, in transformed, IL-3-independent 32D cells, wt p53 overexpression induced different effects. The v-abl-transformed cells manifested a reduction in growth rate, while the v-src-transformed cells underwent monocytic differentiation. These results show that the phenotype effects of wt p53 action(s) can vary as a function of the cellular environment.

Further characterisation of the in situ terminal deoxynucleotidyl transferase (TdT) assay for the flow cytometric analysis of apoptosis in drug resistant and drug sensitive leukaemic cells.

Apoptosis, originally defined by specific morphological changes, is characterised biochemically by non-random cleavage of DNA. Depending on cell type, this DNA cleavage proceeds from 300 and 50kbp fragments prior to, concomitantly with, or in the absence of 180bp integer fragmentation. Incorporation into fragmented DNA of biotin-labelled nucleotides by terminal deoxynucleotidyl transferase (TdT) has recently become a standard flow cytometric assay for the identification and quantitation of apoptosis. Nucleotide incorporation is visualized using avidin-tagged fluorescein isothiocyanate (FITC) (Gorczyca et al.: Cancer Res 53:1945-1951, 1993; Jonker et al.: Cytometry (Suppl 13):Abstr 99A, 1993). Here, we characterise this assay further in three different haemopoietic cell lines. Drug-induced DNA damage is not identified by the TdT assay unless it is coupled to the apoptotic response. This was demonstrated using cells in which activation of the oncogenic Abelson-encoded protein tyrosine kinase suppressed drug-induced apoptosis, but did not inhibit drug-induced DNA damage (by melphalan, hydroxyurea, or etoposide). Furthermore, the TdT assay identifies DNA fragments formed during apoptosis induced by etoposide and N-methylformamide in HL60 and MOLT-4 cells, including those high molecular weight DNA fragments formed in MOLT-4 cells which were not further cleaved to 180-200bp integer fragments. Our results support the use of flow cytometry and the TdT assay to reliably measure apoptotic cells in heterogeneous cell samples.

v-Abl-mediated apoptotic suppression is associated with SHC phosphorylation without concomitant mitogen-activated protein kinase activation.

A temperature-sensitive mutant of the v-Abl protein has previously been shown to exhibit tyrosine protein kinase activity in Interleukin 3 (IL-3)-dependent IC.DP cells grown at the permissive temperature (32 degrees C) but not at the restrictive temperature (39 degrees C). These IC.DP cells are dependent on IL-3 for suppression of apoptosis at 39 degrees C, but at 32 degrees C cells will survive without added growth factor. Both IL-3 and v-Abl stimulated the tyrosine phosphorylation of SHC and GTPase-activating protein. However, while IL-3 stimulated similar levels of tyrosine phosphorylation in p46shc and p52shc, v-Abl preferentially phosphorylated p52shc, an event that occurred within 1 h of temperature switch. v-Abl also differentially associated with p46shc in a temperature-independent manner. In contrast, only IL-3 stimulated detectable increases in both myelin basic protein kinase and mitogen-activated protein (MAP) kinase kinase in in vitro assays, although in more specific MAP kinase activity assays a very slight increase in the activity of this enzyme was observed after 6 h at the permissive temperature. Time course studies suggest that phosphorylation and association of SHC with v-Abl is insufficient to lead to significant activation of MAP kinase and that activation of the MAP kinase kinase/MAP kinase pathway is not required for apoptotic suppression.

Selective repression of v-abl-encoded protein by N-methylisatin-beta-4',4'-diethylthiosemicarbazone and N-allylisatin-beta-4',4'-diallylthiosemicarbazone.

N-Methylisatin-beta-4',4'-diethylthiosemicarbazone (M-IBDET) and N-allylisatin-beta-4',4'-diallylthiosemicarbazone (A-IBDAT) selectively inhibited v-abl protein (P120), an oncogene product associated with tyrosine kinase activity. Concentrations of M-IBDET ranging between 0.17 and 0.64 microM and concentrations of A-IBDAT from 1.45 to 2.9 microM reduced tyrosine kinase activity significantly, whereas 0.64 microM M-IBDET and 2.9 microM A-IBDAT blocked P120 production. Cellular growth rate, protein production, and synthesis of p45 actin and p53 nuclear oncogene were not affected at these conditions. M-IBDET and A-IBDAT selectively suppress the v-abl oncogene as well as Moloney murine leukemia virus production.