Influence of RET/PTC1 and RET/PTC3 oncoproteins in radiation-induced papillary thyroid carcinomas on amounts of cytoskeletal protein species

Cofilin is a mediator of RET-promoted medullary thyroid carcinoma cell migration, invasion and proliferation

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor that originates from parafollicular thyroid C cells and accounts for 5% of thyroid cancers. In inherited cases of MTC, and in about 40% of sporadic cases, activating mutations of the receptor tyrosine kinase proto-oncogene RET are found. Constitutively active RET triggers signaling pathways involved in cell proliferation, survival and motility, but the mechanisms underlying malignant transformation of C-cells have been only partially elucidated. Cofilin is a key regulator of actin cytoskeleton dynamics. A crucial role of cofilin in tumor development, progression, invasion and metastasis has been demonstrated in different human cancers, but no data are available in MTC. Interestingly, RET activation upregulates cofilin gene expression. The aim of this study was to investigate cofilin contribution in invasiveness and growth of MTC cells, and its relevance in the context of mutant RET signaling. We found that cofilin transfection in human MTC cell line TT significantly increased migration (178 ± 44%, p < 0.001), invasion (165 ± 28%, p < 0.01) and proliferation (146 ± 18%, p < 0.001), accompanied by an increase of ERK1/2 phosphorylation (2.23-fold) and cyclin D1 levels (1.43-fold). Accordingly, all these responses were significantly reduced after genetic silencing of cofilin (-55 ± 10% migration, p < 0.001, -41 ± 8% invasion, p < 0.001, -17 ± 3% proliferation, p < 0.001). These results have been confirmed in primary cells cultures obtained from human MTCs. The inhibition of constitutively active RET in TT cells by both the RET pharmacological inhibitor RPI-1 and the transfection of dominant negative RET mutant (RETΔTK) resulted in a reduction of cofilin expression (-37 ± 8%, p < 0.001 and -31 ± 16%, p < 0.01, respectively). Furthermore, RPI-1 inhibitory effects on TT cell migration (-57 ± 13%, p < 0.01), but not on cell proliferation, were completely abolished in cells transfected with cofilin. In conclusion, these data indicate that an unbalanced cofilin expression, induced by oncogenic RET, contributes to promote MTC invasiveness and growth, suggesting the possibility of targeting cofilin pathway for more effective treatment of MTC.

Internal Spreading of Papillary Thyroid Carcinoma: A Case Report and Systemic Review

An 18-year-old female diagnosed finally as PTC with intrathyroid spread was reported, and the diagnosis and surgical treatment of internal spreading of PTC were discussed. One lump was found on the thyroid isthmus by physical examination and B ultrasound, and multiple nodular shadows were found by CT. This patient finally underwent total thyroidectomy with bilateral central node dissection due to multifocal papillary thyroid carcinoma except PTC in the isthmus found in right lobe by intraoperative frozen section. The pathological section showed a major thyroid carcinoma in thyroid isthmus with scattered micropapillary carcinoma around it in the whole thyroid gland. The small lesions are distributed around central lesion in a radial form and the number of small lesions decreases with increased distance from central lesion. PTC with internal spread should be distinguished from multifocal PTC and poorly differentiated PTC in pathology. Thyroid cancerous node had a large diameter; it was likely to have internal spread. Combined imaging before surgery should be valued to diagnose PTC with internal spread. Preoperative CT and intraoperative frozen section are helpful for surgical volume selection of PTC with internal spread.

Epithelial-mesenchymal transition induces endoplasmic-reticulum-stress response in human colorectal tumor cells

Tumor cells are stressed by unfavorable environmental conditions like hypoxia or starvation. Driven by the resulting cellular stress tumor cells undergo epithelial-mesenchymal transition. Additionally, cellular stress is accompanied by endoplasmic reticulum-stress which induces an unfolded protein response. It is unknown if epithelial-mesenchymal transition and endoplasmic reticulum-stress are occurring as independent parallel events or if an interrelationship exists between both of them. Here, we show that in colorectal cancer cells endoplasmic reticulum-stress depends on the induction of ZEB-1, which is a main factor of epithelial-mesenchymal transition. In the absence of ZEB-1 colorectal cancer cells cannot mount endoplasmic reticulum-stress as a reaction on cellular stress situations like hypoxia or starvation. Thus, our data suggest that there is a hierarchy in the development of cellular stress which starts with the presence of environmental stress that induces epithelial-mesenchymal transition which allows finally endoplasmic reticulum-stress. This finding highlights the central role of epithelial-mesenchymal transition during the process of tumorigenesis as epithelial-mesenchymal transition is also associated with chemoresistance and cancer stemness. Consequently, endoplasmic reticulum-stress might be a well suited target for chemotherapy of colorectal cancers.

Analysis of protein species differentiation among mycobacterial low-Mr-secreted proteins by narrow pH range Immobiline gel 2-DE-MALDI-MS

Secreted proteins of bacteria are preferentially capable of interacting with host cells and are therefore of special biological and medical interest. Narrow pH range 2-DE and MALDI-TOFTOF-MS combine high-resolution protein separation with highly sensitive identification of proteins. Secreted proteins of Mycobacterium tuberculosis were separated at the protein species level, distinguishing different protein species of one protein. We focused on the pI range 4.0-4.7 and the Mr range 6-20kDa of the 2-DE pattern. Out of 128 analyzed spots, 121 were identified resulting in 33 different proteins with 277 different protein species, accumulating in a mean of 8.4 protein species per protein. Overrepresentation was found for the protein classes "virulence, detoxification, adaption", "information pathways", "cell wall and cell processes" and "intermediary metabolism and respiration". Thus far, 15 protein species of the ESX-1 family are characterized with 100% sequence coverage. More automated 2-DE procedures and more sensitive identification techniques are required for complete characterization of all of the protein species even in highly enriched samples, such as culture filtrates. Only then the functional level of proteomics will be achieved and potential biomarkers can be postulated at the molecular level.

BIOLOGICAL SIGNIFICANCE

Proteomics is dominated by bottom-up approaches largely ignoring protein speciation. A prerequisite to reach the protein species level is to obtain 100% sequence coverage, which is a major challenge in proteomics. Here we show complete sequence information with a 2-DE-MS approach for 15 protein species. Acetylation of the N-terminus of ESAT-6 inhibits interaction with CFP-10, with direct consequences for pathogen-host interaction. This article is part of a Special Issue entitled: Trends in Microbial Proteomics.