Expression of Endomembrane Calcium Pumps in Colon and Gastric Cancer Cells

Abstract

Calcium mobilization from the endoplasmic reticulum (ER) into the cytosol is a key component of several signaling networks controlling tumor cell growth, differentiation, or apoptosis. Sarco/endoplasmic reticulum calcium transport ATPases (SERCA-type calcium pumps), enzymes that accumulate calcium in the ER, play an important role in these phenomena. We report that SERCA3 expression is significantly reduced or lost in colon carcinomas when compared with normal colonic epithelial cells, which express this enzyme at a high level. To study the involvement of SERCA enzymes in differentiation, in this work differentiation of colon and gastric cancer cell lines was initiated, and the change in the expression of SERCA isoenzymes as well as intracellular calcium levels were investigated. Treatment of the tumor cells with butyrate or other established differentiation inducing agents resulted in a marked and specific induction of the expression of SERCA3, whereas the expression of the ubiquitous SERCA2 enzymes did not change significantly or was reduced. A similar marked increase in SERCA3 expression was found during spontaneous differentiation of post-confluent Caco-2 cells, and this closely correlated with the induction of other known markers of differentiation. Analysis of the expression of the SERCA3 alternative splice isoforms revealed induction of all three known iso-SERCA3 variants (3a, 3b, and 3c). Butyrate treatment of the KATO-III gastric cancer cells led to higher resting cytosolic calcium concentrations and, in accordance with the lower calcium affinity of SERCA3, to diminished ER calcium content. These data taken together indicate a defect in SERCA3 expression in colon cancers as compared with normal colonic epithelium, show that the calcium homeostasis of the endoplasmic reticulum may be remodeled during cellular differentiation, and indicate that SERCA3 constitutes an interesting new differentiation marker that may prove useful for the analysis of the phenotype of gastrointestinal adenocarcinomas.Cellular calcium concentration gradients and calcium ion fluxes are important components of several signaling networks controlling cell growth, differentiation, or apoptosis (1, 2). In a resting cell, the cytosolic free calcium concentration is ϳ50 -100 nM, whereas the endoplasmic reticulum (ER) 1 or the extracellular medium contains calcium in the high micromolar to low millimolar range. Binding of several growth factors, hormones, chemokines, or bioactive peptides to their cell surface receptors leads to the formation of the second messenger inositol 1,4,5-trisphosphate (IP 3 ), which induces calcium release from the endoplasmic reticulum into the cytosol through IP 3 receptor calcium channels. The ensuing decrease of the calcium content of the ER lumen induces the opening of calcium channels in the plasma membrane, allowing calcium influx into the cytosol from the extracellular space. Calcium release from the ER and ensuing calcium influx lead to the augmentation of the cytosolic free calcium concentration. As m...

Histone deacetylase inhibitor- and PMA-induced upregulation of PMCA4b enhances Ca2+ clearance from MCF-7 breast cancer cells

“…A significant increase of 14 SERCA2 expression was observed when cells were treated with PMA alone, while SERCA3 levels increased in valerate-treated cells. These results are in agreement with earlier data showing reduced SERCA3 expression during breast epithelial tumorigenesis [50] and upregulated SERCA3 expression by SCFAs in several lung and colon cancer cell lines [51,52].…”

“…An interesting finding of this study 21 was that PMA alone activated the AP-1 through PKC and MEK1/2, while activation by butyrate depended only on MEK1/2. Correspondingly, expression of SERCA3, a sarco/endoplasmic reticulum-type Ca 2+ pump is also increased during SCFA-induced differentiation of lung and colon cancer cells [51,52], indicating that remodeling of Ca 2+ homeostasis is important in cancer progression and affects more components of the Ca 2+ handling toolkit. We also found a slight elevation of SERCA3 expression in valerate-treated MCF-7 cells, while PMA induced upregulation of SERCA2.…”

The Loss of Sarco/Endoplasmic Reticulum Calcium Transport ATPase 3 Expression Is an Early Event during the Multistep Process of Colon Carcinogenesis

“…21 Briefly, 5-m-thick frozen tissue sections were dried on air, fixed in acetone for 15 minutes, dried, and stored at Ϫ80°C until use. After rehydration in Tris-buffered saline (150 mmol/L NaCl and 10 mmol/L Tris, pH 7.4) containing 0.1% Tween-20 (Trisbuffered saline (TBS)/Tween), nonspecific protein fixation was inhibited by incubation in TBS/Tween supplemented with 5% nonfat dry milk (TBS/Tween/milk) for 30 minutes.…”

“…21 Because the lack of SERCA3 expression therefore appears to be related to the malignant phenotype in colonic epithelium, to better define the role of the loss of SERCA3 expression during the multistep process of colon carcinogenesis, in the present work, we studied SERCA3 expression in normal fetal and adult colonic epithelium; hyperplastic polyps; adenomas; and well, moderately, and poorly differentiated adenocarcinomas. To link the regulation of SERCA3 expression to molecular mechanisms of colon tumorigenesis, we investigated, by using a dominant-negative form of TCF4, the effect of the inhibition of the adenomatous polyposis coli (APC)/␤-catenin/TCF4 pathway, a major oncogenic signal transduction mechanism in the colon, on SERCA3 expression in colon carcinoma cells.…”

Gene expression analysis reveals novel altered genes in nasal polyps

“…seRCA is found in the membrane of the sarcoplasmic reticulum and is responsible for catalyzing the hydrolysis of ATPs for the transport of Ca +2 ions of the cytosol into the lumen of the sarcoplasmic reticulum for muscular excitation and contraction. Mobilization of the Ca +2 ions from the sarcoplasmic reticulum into the cytosol is a key component of the control of tumoral growth, apoptosis and cell differentiation (19), events involved in the formation and establishment of nasal polyps. Ion transport mechanisms altered due to chemical mediators found in the extracellular fluid, mainly histamins, increase the vascular permeability, modifying the electrolyte transport in the cellular membrane and leading to the formation of edema (20).…”