A new paradigm for epidermal growth factor receptor expression exists in PTC and NIFTP regulated by microRNAs

Intoduction

Identification of molecular alterations associated with tumor behavior is necessary to guide clinical management. The 2022 WHO classification has organized the thyroid follicular cell-derived neoplasms into benign, low-risk and high-risk neoplasms, and emphasized the value of biomarkers that may provide differential diagnostic and prognostic information to avoid overtreatment of low risk neoplasms. This work aims to study the epidermal growth factor receptor (EGFR) expression, functional and spatial dynamics in relation to specific miRNAs alterations in papillary thyroid cancer (PTC) and in non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) considered as models of high-risk and low-risk thyroid tumors respectively.

Methods

Primary thyroid cultured cells were used for miRNA gain/loss of function and luciferase reporter assays. Paraffin embedded tissues were used for real time PCR, immuno-fluorescence stain and confocal microscopy experiments.

Results

Our results showed that in PTC, EGFR mRNA is reduced as an effect of miR-146b-5p upregulation. The EGF expression is low and the ERK pathway is inhibited. The EGFR protein high cytoplasmic expression and colocalization with the endosomal/exosomal markers, ALIX and CD63, suggest the occurrence of stress-induced EGFR internalization, accumulation in endosomal vesicles and secretion via exosomes. In NIFTP EGFR transcription is increased in association with downregulation of miR-7-5p and the EGFR/ERK pathway is active indicating dependence on the canonical EGFR pathway for growth.

Conclusion

Downregulation of transcript level along with cytoplasmic accumulation of undegraded protein is a new pattern of EGFR regulation associated with malignancy in thyroid. Further research is needed to elucidate the intracellular trafficking defects responsible for this specific EGFR dynamic in PTC.

The stress-activated protein kinase pathway and the expression of stanniocalcin-1 are regulated by miR-146b-5p in papillary thyroid carcinogenesis

Papillary thyroid cancer (PTC) is the most common type of thyroid cancer. Deciphering the pathophysiological mechanisms that contribute to PTC development is essential to the discovery of optimal diagnostic and therapeutic approaches. MiR-146b-5p has been identified as a cancer-associated microRNA highly up-regulated in PTC. This study explores the hypothesis that miR-146b-5p contributes to papillary thyroid carcinogenesis through regulation of cell signaling pathways in a manner that overcomes the cellular growth suppressive events and provides survival advantage. The effect of miR-146b-5p inhibition on major cancer related signaling pathways and expression of Stanniocalcin-1 (STC1), an emerging molecule associated with stress response and carcinogenesis, was tested in cultured primary thyroid cells using luciferase reporter assays, quantitative real-time PCR, immunofluorescence staining, and flow cytometry. Our results demonstrated that miR-146b-5p inhibits the JNK/AP1 pathway activity and down-regulates the expression of STC-1 in thyroid-cultured cells and in thyroid tissue samples. In the presence of miR-146b-5p, PTC cells were resistant to cell death in response to oxidative stress. This is a novel report that miR-146b-5p directly targets STC1 and regulates the activity of JNK/AP1 pathway. Considering the importance of the JNK/AP1 pathway and STC1 in mediating many physiological and pathological processes like apoptosis, stress response and cellular metabolism, a biological regulator of these pathways would have a great scientific and clinical significance.

Down-regulation of the human major histocompatibility complex class I chain-related gene A (MICA) and its receptor is mediated by microRNA-146b-5p and is a potential mechanism of immunoediting in papillary thyroid carcinoma

Immune escape is one of the main reasons for the rapid progression of cancer and the poor efficacy of immunotherapy. Papillary thyroid cancer (PTC) is usually accompanied by intra-tumoral lymphocytic infiltration. The mechanisms regulating this tumor associated immune response or its evasion are not well understood. The major histocompatibility complex class I chain-related proteins A (MICA) and its receptor the natural killer group 2 member D (NKG2D) are major executers of the anti-tumor defense. This work aimed to study the expression and regulation of MICA-NKG2D and its association with the lymphocytic infiltration and miRNAs in PTC. Expression of MICA and NKG2D in thyroid tissues, and in cultured primary thyroid cancer cells and lymphocytes transfected with miR-146b-5p inhibitor/mimic was tested by RT-PCR. Results were confirmed by immunofluorescence staining and confocal microscopy. MICA is expressed in malignant and benign thyroid tissues with no association with aggressive behavior. Expression of MICA and NKG2D in PTC is concomitant with the presence of tumor associated lymphocytic response and is regulated by miR-146b-5p. MiR-146b-5p indirectly downregulates NKG2D expression in cancer cells and in lymphocytes. Overexpression of miR-146b-5p in PTC down-regulates MICA expression possibly to reduce the immunogenicity of the tumor cells. Targeting of the MICA-NKG2D axis by miR-146b-5p might be one of the ways adopted by thyroid cancer cells to aid the tumor in evading the immune response. The importance of our findings resides in the potential therapeutic use of MICA, NKG2D and miRNA-146b-5p as targets or modulators to enable the immune response against cancer.

Discriminatory miRNAs for the Management of Papillary Thyroid Carcinoma and Noninvasive Follicular Thyroid Neoplasms with Papillary-Like Nuclear Features

BACKGROUND

Papillary thyroid carcinoma (PTC) variants have several overlapping clinical and pathological features. The World Health Organization recently published a new classification of thyroid tumors containing significant revisions. Encapsulated papillary thyroid carcinoma (EPTC) has been recognized as a distinctive variant of PTC. The noninvasive encapsulated follicular variant of PTC has been reclassified as noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP). Different neoplasms are associated with different outcomes and require different clinical management. The objective of this study was to explore the miRNA expression patterns specific for classic PTC (cPTC), EPTC, follicular variant of PTC, and NIFTP in order to identify biomarkers of diagnostic and prognostic utility aiming for better clinical decisions.

METHODS

The expression of 84 miRNAs was determined by quantitative real-time polymerase chain reaction in 113 thyroid tissues of PTC (classic, encapsulated, and follicular), NIFTP, and hyperplasia lesions. Expression of the same miRNAs was tested in pre- and postoperative whole-blood samples.

RESULTS

Several miRNAs were differentially expressed in the different groups. Expression profile of miRNAs in the tissue was similarly reflected in the circulation. Receiver operating characteristic curve analysis showed that miR-7-5p, miR-222-3p, and miR-146b-5p can discriminate between the different groups with high sensitivity and specificity. Downregulation of miR-144-3p, miR-15a-5p, miR-20a-5p, miR-32-5p miR-142-5p, miR-143-3p, and miR-20b-5p is associated with aggressive behavior in cPTC. Circulating miR-146b-5p, miR-222-3p, miR-155-5p, and miR-378a-3p are potential diagnostic and follow up biomarkers for PTC.

CONCLUSION

Downregulation of miR-7-5p discriminates NIFTP from hyperplasia. Upregulation of miR-222-3p discriminates follicular variant of PTC from NIFTP. High levels of miR-146b-5p distinctively characterize cPTC. These miRNAs are useful biomarkers in the diagnosis of PTC and NIFTP, and help to avoid unnecessary thyroidectomy and improve clinical management.