thapsigargin and Thyroid-Neoplasms

The molecular carcinogenesis of lung cancer has yet to be clearly elucidated. We investigated the possible oncogenic function of SEC62 in lung cancer, which was predicted based on our previous findings that lung and thyroid cancer tissue samples exhibited increased Sec62 protein levels. The SEC62 gene locus is at 3q26.2, and 3q amplification is reportedly the most common genomic alteration in non-small cell lung cancer. We analyzed SEC62 mRNA and protein levels in tissue samples from lung cancer patients by real-time quantitative PCR, Western blot, and IHC and found significantly increased SEC62 mRNA and protein levels in tumors compared with tumor-free tissue samples from the same patients. Correlation analyses revealed significantly higher Sec62 levels in tumors with lymph node metastases compared with nonmetastatic tumors, as well as in poorly compared with moderately differentiated tumors. On the basis of these promising results, we examined the role of Sec62 in cancer cell biology in vitro. Cell migration assays with lung and thyroid cancer cells showed distinct stimulation of migration in SEC62-overexpressing cells and inhibition of migration in Sec62-depleted cells. Moreover, we found that SEC62 silencing sensitized the cells to thapsigargin-induced endoplasmic reticulum stress. Thus, our results indicate that SEC62 represents a potential candidate oncogene in the amplified 3q region in cases of non-small cell lung cancer and harbors various functions in cancer cell biology.

Topics: Adaptor Proteins, Signal Transducing; Blotting, Western; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Cell Movement; Chromosomes, Human, Pair 3; DNA Topoisomerases, Type II; DNA-Binding Proteins; Endoplasmic Reticulum Stress; Enzyme Inhibitors; Gene Amplification; Gene Silencing; Humans; Immunohistochemistry; Lung Neoplasms; Membrane Transport Proteins; Real-Time Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Thapsigargin; Thyroid Neoplasms

Extracellular nucleotides like ATP that activate the Ca2+ -phosphatidylinositol (PI) signalling pathway have been suggested to participate in the regulation of normal human thyroid function. We examined, whether P2y-purinergic receptors are expressed on human thyroid cancer cells and whether post-receptor Ca2+ signalling is altered by malignant transformation. Extracellular ATP caused a biphasic increase in cytosolic free Ca2+ ([Ca2+]i) in normal human thyrocytes and in human follicular (FTC) and papillary (PTC) thyroid carcinoma cells. In FTC and PTC cell lines the dose-response curves for ATP-induced changes in [Ca2+]i were shifted to the right when compared with normal thyrocytes, whereas in undifferentiated thyroid carcinoma (UTC) cells even high concentrations of ATP (500 microM) failed to stimulate a rise in [Ca2+]i. By contrast, ATP stimulated inositol 1,4,5-trisphosphate (IP3) formation and capacitative Ca2+ entry was operational as judged by thapsigargin in normal thyrocytes and all thyroid cancer cells. Thus, P2y-purinergic receptors are expressed on thyroid tumor cells independent of degree of differentiation. In UTC cells, however, impairment in the Ca2+ -phosphatidylinositol (PI) signalling cascade occurs distal to the formation of IP3 and proximal to the activation of capacitative Ca2+ entry. Disturbed ATP-induced Ca2+ -signalling and alterations in the Ca2+ -PI signalling cascade may contribute to decreased expression or loss of specific thyroid functions in thyroid cancer cells.

Topics: Adenosine Triphosphate; Calcium; Carcinoma, Papillary; Carcinoma, Papillary, Follicular; Cytosol; Extracellular Space; Humans; Inositol 1,4,5-Trisphosphate; Signal Transduction; Thapsigargin; Thyroid Gland; Thyroid Neoplasms; Tumor Cells, Cultured