The free cytoplasmic calcium concentration of tumorigenic and non-tumorigenic human somatic cell hybrids

Topology and adenocarcinoma cell localization dataset on the labyrinthin diapeutic biomarker

OBJECTIVE

The discovery and characterization of tumor associated antigens is increasingly important to advance the field of immuno-oncology. In this regard, labyrinthin has been implicated as a neoantigen found on the cell surface of adenocarcinomas. Data on the (1) topology, (2) amino acid (a.a.) homology analyses and (3) cell surface localization of labyrinthin by fluorescent activated cell sorter (FACS) are studied in support of labyrinthin as a novel, pan-adenocarcinoma marker.

RESULTS

Bioinformatics analyses predict labyrinthin as a type II protein with calcium binding domain(s), N-myristoylation sites, and kinase II phosphorylation sites. Sequence homologies for labyrinthin (255 a.a.) were found vs. the intracellular aspartyl/asparaginyl beta-hydroxylase (ASPH; 758 a.a.) and the ASPH-gene related protein junctate (299 a.a.), which are both type II proteins. Labyrinthin was detected by FACS on only non-permeablized A549 human lung adenocarcinoma cells, but not on normal WI-38 human lung fibroblasts nor primary cultures of normal human glandular-related cells. Microscopic images of immunofluorescent labelled MCA 44-3A6 binding to A549 cells at random cell cycle stages complement the FACS results by further showing that labyrinthin persisted on the cell surfaces along with some cell internalization for greater than 20 min.

Labyrinthin: A distinct pan-adenocarcinoma diagnostic and immunotherapeutic tumor specific antigen

Structural analysis and detection of optimal cell surface localization of labyrinthin, a pan-adenocarcinoma target, was studied with respect to adenocarcinoma specificity vs. normal and non-adenocarcinoma cells. Patient-derived tissue microarray immunohistochemistry (IHC) was performed on 729 commercially prepared tissue blocks of lung, colon, breast, pancreas, prostate, and ovary cancers combined, plus a National Cancer Institute (NCI) tissue microarray derived from another 236 cases. The results confirmed that anti-labyrinthin mouse monoclonal MCA 44-3A6 antibody recognized adenocarcinomas, but not normal or non-adenocarcinoma cancer cells. The consensus of multiple topology analysis programs on labyrinthin (255 amino acids) estimate a type II cell membrane associated protein with an N-terminus signal peptide. However, because the labyrinthin sequence is enveloped within the 758 amino acids of the intracellular aspartyl/asparaginyl beta-hydroxylase (ASPH), a purported tumor associated antigen, standard IHC methods that permeabilize cells can expose common epitopes. To circumvent antibody cross-reactivity, cell surface labyrinthin was distinguished from intracellular ASPH by FACS analysis of permeabilized vs non-permeabilized cells. All permeabilized normal, adeno-and non-adenocarcinoma cells produced a strong MCA 44-3A6 binding signal, likely reflecting co-recognition of intracellular ASPH proteins along with internalized labyrinthin, but in non-permeabilized cells only adenocarcinoma cells were positive for labyrinthin. Confocal microscopy confirmed the FACS results. Labyrinthin as a functional cell-surface marker was suggested when: 1) WI-38 normal lung fibroblasts transfected with labyrinthin sense cDNA displayed a cancerous phenotype; 2) antisense transfection of A549 human lung adenocarcinoma cells appeared more normal; and 3) MCA44-3A6 suppressed A549 cell proliferation. Collectively, the data indicate that labyrinthin is a unique, promising adenocarcinoma tumor-specific antigen and therapeutic target. The study also raises a controversial issue on the extent, specificity, and usefulness of ASPH as an adenocarcinoma tumor-associated antigen.

Modulation of intracellular calcium and calmodulin by melatonin in MCF-7 human breast cancer cells

The pineal hormone, melatonin, has been shown to inhibit the proliferation of the estrogen receptor alpha (ERalpha)-positive macrophage chemotactic factor (MCF)-7 human breast cancer cells. Previous studies from other systems indicate that melatonin modulates the calcium (Ca2+)/calmodulin (CaM) signaling pathway either by changing intracellular calcium concentration ([Ca2+]i) via activation of its G-protein coupled membrane receptors, or through a direct interaction with CaM. In this study, although melatonin alone had no effect on basal [Ca2+]i in MCF-7 cells, it significantly enhanced the elevation of [Ca2+]i induction by extracellular adenosine triphosphate (ATP), which increases [Ca2+]i via the G protein-coupled P2y-purinoceptor and the phospholipase C (PLC) pathway. Pretreatment of MCF-7 cells with 10(-7) M melatonin increased the 10(-5) M ATP-induced [Ca2+]i peak change from 79.4 +/- 11.6 nM to 146.2 +/- 22.3 nM. Furthermore, without changing total cellular CaM levels, melatonin markedly increased the amount of membrane-bound CaM to 237 and 162% of control levels after I and 6 hr of treatment, respectively. Cytosolic CaM levels were also elevated to 172% of control after 6 hr of melatonin treatment. Correlative growth studies demonstrated that ATP (10(-5) M) can stimulate MCF-7 cell growth, that melatonin can suppress MCF-7 cell proliferation, but that pretreatment of MCF-7 cells with melatonin followed by ATP(10(-5) M), like 10(-4) M ATP can further suppress MCF-7 cell proliferation; this indicates that melatonin's potentiation of ATP induced [Ca2+]i may be above the threshold for cell growth. Given the important role of [Ca2+]i and CaM in tumor cell homeostasis and proliferation and melatonin's modulation of [Ca2+]i, melatonin's effects on the Ca2+/CaM signaling pathway may play an important role in mediating the growth-inhibitory effect of melatonin on MCF-7 human breast cancer cells.

Syndecan-4 proteoglycan cytoplasmic domain and phosphatidylinositol 4,5-bisphosphate coordinately regulate protein kinase C activity

Phosphatidylinositol 4,5-bisphosphate (PIP2) is involved in the organization of the actin cytoskeleton by regulating actin-associated proteins. The transmembrane heparan sulfate proteoglycan syndecan-4 also plays a critical role in protein kinase C (PKC) signaling in the formation of focal adhesions and actin stress fibers. The cytoplasmic domain of syndecan-4 core protein directly interacts with and potentiates PKCalpha activity, and it can directly interact with the phos- phoinositide PIP2. We, therefore, investigated whether the interaction of inositol phosphates and inositol phospholipids with syndecan-4 could regulate PKC activity. Data from in vitro kinase assays using purified PKCalpha beta gamma show that in the absence of phosphatidylserine and diolein, PIP2 increased the extent of autophosphorylation of PKCalpha beta gamma and partially activated it to phosphorylate both histone III-S and an epidermal growth factor receptor peptide. This activity was dose-dependent, and its calcium dependence varied with PKC isotype/source. Addition of the cytoplasmic syndecan-4 peptide, but not equivalent syndecan-1 or syndecan-2 peptides, potentiated the partial activation of PKCalpha beta gamma by PIP2, resulting in activity greater than that observed with phosphatidylserine, diolein, and calcium. This study indicates that syndecan-4 cytoplasmic domain may bind both PIP2 and PKCalpha, localize them to forming focal adhesions, and potentiate PKCalpha activity there.

Determination of eight elements in six human cancer cell lines and two human normal cell lines by PIXE

Gastric, hepatic, and pulmonary cancer cell lines, and the third passage of normal gastric and pulmonary cell lines were analyzed by proton induced X-ray emission (PIXE) method. The contents of element Sr, Ca, Fe, Zn, P, K, Cu, and As in the cell lines were determined. The Sr, Ca, Fe, Zn, and As contents in cancer cell lines were significantly lower than those in the normal cell lines (p less than 0.05), whereas there were no significant differences for the P, K, and Cu contents (p greater than 0.1). The results suggest that the need of some essential elements has been diminished in cancer cell proliferation.

Calcium uptake by leukemic and normal T-lymphocytes exposed to low frequency magnetic fields

Calcium-ion uptake by normal and leukemia lymphocytes increased during a 30-min exposure to a 13.6 Hz, sinusoidal magnetic field at 20 microT peak. The time-varying field was horizontal and parallel to a 16.5 microT component of the ambient static magnetic field. The uptake of 45Ca2+ increased 102% in a line of murine, cytotoxic T-lymphocytes (C57B1/6-derived CTLL-1), increased 126% in freshly-isolated spleen lymphocytes (C57B1/6 mice), and increased 75% in a line of lymphoma cells (C57B1/6-derived EL4). In contrast, there was no effect when the same field was applied for 30 min immediately before--as opposed to during--incorporation of calcium ions. When spleen lymphocytes were exposed during incubation with 45Ca2+ to a 60 Hz magnetic field at 20 microT peak, a small but statistically significant increase (37%) in uptake of the labeled ions occurred. These results indicate that weak, alternating magnetic fields might affect calcium-dependent functions of normal and leukemic lymphocytes.

Microfilament organization correlates with increased cellular content of gelsolin

The relative amounts of intracellular gelsolin were determined in a number of human somatic cell hybrids and parental cell lines which greatly differ in their microfilament organizations. In contrast to the disruptive effect of gelsolin on actin filament formation in vitro, there is a correlation between the degree of microfilament organization and the amount of gelsolin within these cell lines.

Intracellular distribution of calcium and zinc in normal, hyperplastic, and neoplastic human prostate: X-ray microanalysis of freeze-dried cryosections

X-ray microanalysis has been performed on freeze-dried cryosections of normal, hyperplastic, and neoplastic human prostates. Needle biopsies from prostates suspected to be malignant were collected from ten patients. Seven of these patients had fully developed nodular hyperplasia, whereas the remaining three specimens were histologically classified as moderately differentiated adenocarcinomas. Prostates with normal light microscopic appearance were obtained from two brain-dead kidney donors. The concentration of calcium in secretory vesicles was found to be several orders of magnitude higher than the concentration of magnesium and zinc in all of the glands studied, which is consistent with calcium being the major cation secreted by the prostatic acinar cells. Some elderly prostates and neoplastic prostates revealed even lower mean zinc:calcium ratios in secretory vesicles. Even though both elements varied considerably, the wide variation of the zinc:calcium ratios was due mainly to variations in the concentration of zinc. Large, electron-dense bodies occasionally were found in the cytoplasm of prostatic acinar cells. These bodies contained high concentrations of sulphur which by far was the dominating element.

Calcium-binding proteins in carcinoma, neuroblastoma and glioma cell lines

Antisera against the Ca2+-binding proteins parvalbumin, calbindin D-28K, and the S-100 proteins were used to study the distribution of their target proteins in selected human carcinoma (LICR-HN6;Caco-2), mouse neuroblastoma (clone NB-2a), and rat glioma cell lines (clone C-6). Pronounced staining with anti-parvalbumin was observed in the cytosol of all cells as well as in some nuclei, in particular, mitotic nuclei were highly immuno-reactive. Applying light and immune-electron microscopy (colloidal gold labelling) the parvalbumin-fluorescence was associated with filaments in the LICR-HN6 cells. However, this immunoreactivity was not a result of the presence of parvalbumin itself--as shown by biochemical analyses (HPLC, 2D-PAGE)--but was due to the presence of a Ca2+-binding and tumour-associated protein with similar biochemical and immunological properties. S-100 proteins were present in all tumour cell lines but their intracellular distribution was different from calbindin D-28K. Calbindin-immunoreactivity was found on the membranes of the carcinoma cell lines whereas neuroblastoma and glioma cells remained unlabelled. It is suggested that these proteins might be involved in the modulation of the enhanced stimulation of Ca2+-dependent processes occurring in tumour cells.

Ca2+ and calmodulin are involved in the processes conferring stability to DNA in proliferating neoplastic cells

We have examined, in proliferating neoplastic cells, the effect on DNA of EGTA (a chelator of Ca2+) and W7 (an inhibitor of calmodulin). The treatment results in release of single-stranded DNA fragments (2-10 kb) from pre-labelled HMW DNA. When DNA from synchronized neoplastic cells in S phase is examined, almost all pre-labelled DNA appears as short fragments. However, fragmentation does not occur in growth-arrested cells or in normal cells. Furthermore, fragmentation can be prevented by incubating cells in excessive amounts of Ca2+. Hence Ca2+ and the Ca2+-binding protein calmodulin are involved in the processes conferring stability to DNA in proliferating neoplastic cells.