Expression of MRP1 and ABCG2 is associated with adverse clinical outcomes of papillary thyroid carcinoma with a solid component

Improving cancer immunotherapy by preventing cancer stem cell and immune cell linking in the tumor microenvironment

Cancer stem cells are the key link between malignant tumor progression and drug resistance. This cell population has special properties that are different from those of conventional tumor cells, and the role of cancer stem cell-related exosomes in progression of tumor malignancy is becoming increasingly clear. Cancer stem cell-derived exosomes carry a variety of functional molecules involved in regulation of the microenvironment, especially with regard to immune cells, but how these exosomes exert their functions and the specific mechanisms need to be further clarified. Here, we summarize the role of cancer stem cell exosomes in regulating immune cells in detail, aiming to provide new insights for subsequent targeted drug development and clinical strategy formulation.

Harnessing cancer stem cell-derived exosomes to improve cancer therapy

Cancer stem cells (CSCs) are the key "seeds" for tumor initiation and development, metastasis, and recurrence. Because of the function of CSCs in tumor development and progression, research in this field has intensified and CSCs are viewed as a new therapeutic target. Exosomes carrying a wide range of DNA, RNA, lipids, metabolites, and cytosolic and cell-surface proteins are released outside of the originating cells through the fusion of multivesicular endosomes or multivesicular bodies with the plasma membrane. It has become evident that CSC-derived exosomes play a significant role in almost all "hallmarks" of cancer. For example, exosomes from CSCs can maintain a steady state of self-renewal in the tumor microenvironment and regulate microenvironmental cells or distant cells to help cancer cells escape immune surveillance and induce immune tolerance. However, the function and therapeutic value of CSC-derived exosomes and the underlying molecular mechanisms are still largely undefined. To provide an overview of the possible role of CSC-derived exosomes and targeting strategies, we summarize relevant research progress, highlight the potential impact of detecting or targeting CSC-derived exosomes on cancer treatment, and discuss opportunities and challenges based on our experience and insights in this research area. A more thorough understanding of the characteristics and function of CSC-derived exosomes may open new avenues to the development of new clinical diagnostic/prognostic tools and therapies to prevent tumor resistance and relapse.

Significance of miRNAs on the thyroid cancer progression and resistance to treatment with special attention to the role of cross-talk between signaling pathways

Thyroid cancer (TC) is the most prevalent endocrine malignant tumor. It has many types, the Papillary thyroid cancer (PTC)(most common and follicular thyroid carcinoma (FTC). Several risk factors have been associated with TC radiation exposure, autoimmunity, and genetics. Microribonucleic acids (miRNAs) are the most important genetic determinants of TC. They are small chains of nucleic acids that are able to inhibit the expression of several target genes. They could target several genes involved in TC proliferation, angiogenesis, apoptosis, development, and even resistance to therapy. Besides, they could influence the stemness of TC. Moreover, they could regulate several signaling pathways such as WNT/β-catenin, PI3K/AKT/mTOR axis, JAK/STAT, TGF- β, EGFR, and P53. Besides signaling pathways, miRNAs are also involved in the resistance of TC to major treatments such as surgery, thyroid hormone-inhibiting therapy, radioactive iodine, and adjuvant radiation. The stability and sensitivity of several miRNAs might be exploited as an approach for the usage of miRNAs as diagnostic and/or prognostic tools in TC.

Identification and Validation of Prognostic Related Hallmark ATP-Binding Cassette Transporters Associated With Immune Cell Infiltration Patterns in Thyroid Carcinoma

ATP-binding cassette (ABC) transporters are a large superfamily of membrane proteins that facilitate the translocation of heterogeneous substrates. Studies indicate that ABC transporters may play important roles in various carcinomas. However, the correlation between ABC transporters and immunomodulation in thyroid carcinoma (TC), as well as the prognoses for this disease, is poorly understood.TC data from The Cancer Genome Atlas (TCGA) database were used to identify prognostic hallmark ABC transporters associated with immune cell infiltration patterns via multiple bioinformatic analyses. Thereafter, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate the expression of these selected hallmark ABC transporters in both TC and para-cancerous thyroid tissues. Of a total of 49 ABC transporters, five (ABCA8, ABCA12, ABCB6, ABCB8, and ABCC10) were identified as hallmark ABC transporters. All five were differentially expressed in TC and associated with the relapse-free survival rates of patients with TC. Immunoregulation by these five hallmark ABC transporters involved the modulation of various aspects of immune cell infiltration, such as hot or cold tumor subsets and the abundances of infiltrating immune cells, as well as specific immunomodulators and chemokines. Besides the diverse significantly correlated factors, the five hallmark ABC transporters and correlated genes were most highly enriched in plasma membrane, transporter activity, and transmembrane transport of small molecules. In addition, many chemicals, namely bisphenol A and vincristine, affected the expression of these five transporters. The qRT-PCR results of collected TC and para-cancerous thyroid tissues were consistent with those of TCGA. The findings in this study may reveal the role played by these five hallmark ABC transporters in regulating immune cell infiltration patterns in TC as well as the molecular mechanisms underlying their functions, leading to a better understanding of their potential prognostic and immunotherapeutic values.

Impact of transforming growth factor beta 1 on normal and thyroid cancer side population cells

PURPOSE

To determine the impact of exogenous transforming growth factor beta 1 (TGF-β1) on side population (SP) cells isolated from normal, papillary thyroid cancer and anaplastic thyroid cancer cell lines and from human thyroid tissues.

METHODS

All cell populations were stained with Hoechst 33342 and analysed using dual wavelength flow cytometry to identify SP cells. This SP assay was used to assess the impact of TGF-β1 treatment and withdrawal of treatment on SP percentages. Semi-quantitative and quantitative PCR were used for molecular analysis of cells pre and post TGF-β1 treatment.

RESULTS

All cell lines expressed mRNA for both TGFB1 and its receptors, as well as showing variable expression of CDH1 and CDH2, with expressing of CDH1 being highest and CDH2 being lowest in the normal cell line. Exposure to exogenous TGF-β1 resulted in a reduction in mRNA expression of ABCG2 compared to controls which was significant between control and treated cancer cell lines. SP cells were isolated from primary human thyroid tissues, with numbers being significantly higher in papillary thyroid cancers. Exposure to TGF-β1 decreased the SP percentage in both thyroid cancer cell lines and completely abrogated these cells in the primary papillary thyroid cancer cultures. On withdrawal of TGF-β1 the SP phenotype was restored in the cancer cell lines and SP percentages increased to above that of untreated cells.

CONCLUSIONS

TGF-β1 exposure transiently regulates thyroid cancer SP cells, leading to a reduction in SP percentages, while withdrawal of TGF-β1 results in restoration of the SP phenotype.

Diagnostic and prognostic impact of cytokeratin 19 expression analysis in human tumors: a tissue microarray study of 13,172 tumors

To evaluate cytokeratin 19 (CK19) expression in normal and cancerous tissues, 15,977 samples from 122 tumor types and 608 samples of 76 normal tissue types were analyzed by immunohistochemistry (IHC). In normal tissues, CK19 expression occurred in epithelial cells of most glandular organs but was strictly limited to the basal cell layer of nonkeratinizing squamous epithelium and absent in the skin. CK19 expression in ≥90% of cases was seen in 34% of the tumor entities including the adenocarcinomas of the pancreas (99.4%), colorectum (99.8%), esophagus (98.7%), and stomach (97.7%), as well as breast cancer (90.0%-100%), high-grade serous (99.1%) or endometrioid (97.8%) ovarian cancer, and urothelial carcinoma (92.6%-100%). A low CK19 positivity rate (0.1-10%) was seen in 5 of 122 tumor entities including hepatocellular carcinoma and seminoma. A comparison of tumor versus normal tissue findings demonstrated that upregulation and downregulation of CK19 can occur in cancer and that both alterations can be linked to unfavorable phenotypes. CK19 downregulation was linked to high grade (p = 0.0017) and loss of estrogen receptor- and progesterone receptor-expression (p < 0.0001 each) in invasive breast carcinoma of no special type. CK19 upregulation was linked to nodal metastases in neuroendocrine tumors and papillary thyroid carcinomas (p < 0.05 each) and to poor grade in clear cell renal cell carcinoma (p < 0.05). CK19 upregulation was particularly common in squamous cell carcinomas. We concluded that CK19 IHC might separate primary liver cell carcinoma from liver metastases, seminoma from other testicular tumors, and helps in the detection of early neoplastic transformation in squamous epithelium.

Targeting cancer stem cells for reversing therapy resistance: mechanism, signaling, and prospective agents

Cancer stem cells (CSCs) show a self-renewal capacity and differentiation potential that contribute to tumor progression and therapy resistance. However, the underlying processes are still unclear. Elucidation of the key hallmarks and resistance mechanisms of CSCs may help improve patient outcomes and reduce relapse by altering therapeutic regimens. Here, we reviewed the identification of CSCs, the intrinsic and extrinsic mechanisms of therapy resistance in CSCs, the signaling pathways of CSCs that mediate treatment failure, and potential CSC-targeting agents in various tumors from the clinical perspective. Targeting the mechanisms and pathways described here might contribute to further drug discovery and therapy.

Thyroid Hürthle Cell Carcinoma: Clinical, Pathological, and Molecular Features

Simple Summary

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is characterized by its large, granular and eosinophilic cytoplasm, due to an excessive number of mitochondria. Hürthle cells can be identified only after fine needle aspiration cytology biopsy or by histological diagnosis after the surgical operation. Published studies on HCC indicate its putative high aggressiveness. In this article, current knowledge of HCC focusing on clinical features, cytopathological features, genetic changes, as well as pitfalls in diagnosis are reviewed in order to improve clinical management.

Abstract

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is considered to be more aggressive than non-oncocytic thyroid carcinomas. However, due to its rarity, the pathological characteristics and biological behavior of HCC remain to be elucidated. The Hürthle cell is characterized cytologically as a large cell with abundant eosinophilic, granular cytoplasm, and a large hyperchromatic nucleus with a prominent nucleolus. Cytoplasmic granularity is due to the presence of numerous mitochondria. These mitochondria display packed stacking cristae and are arranged in the center. HCC is more often observed in females in their 50–60s. Preoperative diagnosis is challenging, but indicators of malignancy are male, older age, tumor size > 4 cm, a solid nodule with an irregular border, or the presence of psammoma calcifications according to ultrasound. Thyroid lobectomy alone is sufficient treatment for small, unifocal, intrathyroidal carcinomas, or clinically detectable cervical nodal metastases, but total thyroidectomy is recommended for tumors larger than 4 cm. The effectiveness of radioactive iodine is still debated. Molecular changes involve cellular signaling pathways and mitochondria-related DNA. Current knowledge of Hürthle cell carcinoma, including clinical, pathological, and molecular features, with the aim of improving clinical management, is reviewed.

Solid variant of papillary thyroid carcinoma: an under-recognized entity

Solid variant of papillary thyroid carcinoma (SVPTC) is a rare morphological variant of papillary thyroid carcinoma (PTC). SVPTC is histologically characterized by predominant solid, trabecular and insular nests of tumor cells while cytological features of PTC such as nuclear grooves and nuclear inclusions are preserved. In fine needle aspiration cytology smears, tumor cells of SVPTC may be presented in cohesive, syncytial or trabecular clusters accompanied by some discohesiveness in the absence of necrosis. Although SVPTC and poorly differentiated thyroid carcinoma (PDTC) share similar histological findings of solid nests, SVPTC can be differentiated from PDTC in the lack of tumor necrosis, severe nuclear atypia, and a higher mitotic index. Immunohistochemical expression of CK19 and HBME-1, common markers of PTC, is decreased in solid nests of SVPTC. In pediatric patients exposed to radiation after the Chernobyl nuclear accident, there was a higher prevalence of SVPTC with RET/PTC3 type rearrangement. BRAF mutations are also reported in a small number of adult patients with SVPTC without any prior radiation exposure. Patients with SVPTC may have a slightly higher incidence of metastasis and recurrence of the tumor compared to conventional PTC, although overall survival rate is comparable. In this article, the current knowledge of SVPTC will be reviewed and discussed with an emphasis on the histopathological feature.

Insights into new mechanisms and models of cancer stem cell multidrug resistance

The acquisition of genetic alterations, clonal evolution, and the tumor microenvironment promote cancer progression, metastasis and therapy resistance. These events correspond to the establishment of the great phenotypic heterogeneity and plasticity of cancer cells that contribute to tumor progression and resistant disease. Targeting resistant cancers is a major challenge in oncology; however, the underlying processes are not yet fully understood. Even though current treatments can reduce tumor size and increase life expectancy, relapse and multidrug resistance (MDR) ultimately remain the second cause of death in developed countries. Recent evidence points toward stem-like phenotypes in cancer cells, promoted by cancer stem cells (CSCs), as the main culprit of cancer relapse, resistance (radiotherapy, hormone therapy, and/or chemotherapy) and metastasis. Many mechanisms have been proposed for CSC resistance, such as drug efflux through ABC transporters, overactivation of the DNA damage response (DDR), apoptosis evasion, prosurvival pathways activation, cell cycle promotion and/or cell metabolic alterations. Nonetheless, targeted therapy toward these specific CSC mechanisms is only partially effective to prevent or abolish resistance, suggesting underlying additional causes for CSC resilience. This article aims to provide an integrated picture of the MDR mechanisms that operate in CSCs' behavior and to propose a novel model of tumor evolution during chemotherapy. Targeting the pathways mentioned here might hold promise and reveal new strategies for future clinical therapeutic approaches.

Trop2 Promotes Multidrug Resistance by Regulating Notch1 Signaling Pathway in Gastric Cancer Cells

BACKGROUND Chemotherapy is widely used in gastric cancer treatment, but multidrug resistance remains a leading cause of chemotherapy failure. Trop2 is highly expressed in gastric tumor tissues and greatly influences cancer progression. However, little is known about the relationship between Trop2 and drug resistance in gastric cancer. MATERIAL AND METHODS In the present study, Trop2 was knocked down in BGC823 cells and overexpressed in HGC27. CCK-8 assay was performed to explore the relationship of Trop2 expression and cell proliferation treated with anticancer drugs. Flow cytometry was performed to assess the relationship between Trop2 and cell apoptosis after chemotherapy. Subcutaneous xenograft models were generated to explore the curative effect of DDP to GC in vivo. MRP1 and Notch1 expressions were assessed by Western blot. RESULTS Trop2 decreased cell proliferation inhibition and apoptosis after chemotherapeutic treatments. DDP showed stronger therapeutic effects on Trop2-knockdown tumor than control in vivo. MRP1 and Notch1 signaling pathway were confirmed to participate in Trop2-induced drug resistance. CONCLUSIONS Our findings suggest that Trop2 promotes the resistance of gastric cancer to chemotherapy by activating the Notch1 pathway.

Solid papillary thyroid carcinoma with Hashimoto's thyroiditis: description of a further case with challenging cytological features

Solid papillary thyroid carcinoma (SV-PTC) is a rare variant which is mainly observed in young patients with a history of exposure to ionising radiations. Neoplasms belonging to such category generally carry RET-PTC (REarranged during Transfection- Papillary Thyroid Carcinoma) fusions and seem to have a slightly worse prognosis with respect to classical and follicular variants of papillary thyroid carcinoma (PTC), though consistent prognostic and survival data are scarce. SV-PTC should be differentiated from trabecular-insular poorly differentiated thyroid carcinomas, which occur in a different age group and carry a dismal prognosis. These latter tumours do not show the typical nuclear features of PTC and show tumour necrosis with an high mitotic activity. In this report a further case of SV-PTC is described which was associated to Hashimoto's thyroiditis, a finding never described in the cytological literature up to now for SV-PTC; this association created further differential diagnostic problems. The neoplasm displayed RET-PTC1 fusion.

Recent Advances in the Classification of Low-grade Papillary-like Thyroid Neoplasms and Aggressive Papillary Thyroid Carcinomas: Evolution of Diagnostic Criteria

Papillary thyroid carcinomas account for ∼80% of well-differentiated thyroid tumors. During the past decade, several new variants of papillary-like thyroid neoplasms and papillary thyroid carcinomas have been recognized. Some of these neoplasms that were previously classified as malignant have been reclassified as low-grade neoplasms, as the diagnostic criteria have evolved. Similarly, some of the papillary thyroid carcinomas that were previously classified as conventional or classic papillary thyroid carcinomas have now been recognized as more aggressive variants of papillary thyroid carcinomas. Recognizing these differences becomes more important for the proper medical, surgical, and radiotherapeutic management of patients with these neoplasms.

Loss of One or Two PATZ1 Alleles Has a Critical Role in the Progression of Thyroid Carcinomas Induced by the RET/PTC1 Oncogene

POZ/BTB and AT-hook-containing zinc finger protein 1 (PATZ1) is an emerging cancer-related gene that is downregulated in different human malignancies, including thyroid cancer, where its levels gradually decrease going from papillary thyroid carcinomas (PTC) to poorly differentiated and undifferentiated highly aggressive anaplastic carcinomas (ATC). The restoration of PATZ1 expression in thyroid cancer cells reverted their malignant phenotype by inducing mesenchymal-to-epithelial transition, thus validating a tumor suppressor role for PATZ1 and suggesting its involvement in thyroid cancer progression. Here, we investigated the consequences of the homozygous and heterozygous loss of PATZ1 in the context of a mouse modeling of PTC, represented by mice carrying the RET/PTC1 oncogene under the thyroid specific control of the thyroglobulin promoter RET/PTC1 (RET/PTC1^TG). The phenotypic analysis of RET/PTC1^TG mice intercrossed with Patz1-knockout mice revealed that deficiency of both Patz1 alleles enhanced thyroid cancer incidence in RET/PTC1^TG mice, but not the heterozygous knockout of the Patz1 gene. However, both RET/PTC1^TG;Patz1^+/− and RET/PTC1^TG;Patz1^−/− mice developed a more aggressive thyroid cancer phenotype—characterized by higher Ki-67 expression, presence of ATCs, and increased incidence of solid variants of PTC—than that shown by RET/PTC1^TG; Patz1^+/+ compound mice. These results confirm that PATZ1 downregulation has a critical role in thyroid carcinogenesis, showing that it cooperates with RET/PTC1 in thyroid cancer progression.

Tyrphostin RG14620 selectively reverses ABCG2-mediated multidrug resistance in cancer cell lines

The multidrug resistance (MDR) phenotype associated with the overexpression of ATP-binding cassette (ABC) drug transporters ABCB1, ABCC1 and ABCG2 is a major obstacle in cancer chemotherapy. Numerous epidermal growth factor receptor (EGFR) inhibitors have previously been shown capable of reversing MDR in ABCG2-overexpressing cancer cells. However, most of them are not transporter-specific due to the substantial overlapping substrate specificity among the transporters. In this study, we investigated the interaction between ABCG2 and tyrphostin RG14620, an EGFR inhibitor of the tyrphostin family, in multidrug-resistant cancer cell lines. We found that at nontoxic concentrations, tyrphostin RG14620 enhances drug-induced apoptosis and restores chemosensitivity to ABCG2-overexpressing multidrug-resistant cancer cells. More importantly, tyrphostin RG14620 is selective to ABCG2 relative to ABCB1 and ABCC1. Our findings were further supported by biochemical assays demonstrating that tyrphostin RG14620 stimulates ATP hydrolysis and inhibits photoaffinity labeling of ABCG2 with IAAP, and by a docking analysis of tyrphostin RG14620 in the drug-binding pocket of this transporter. Taken together, our findings indicate that tyrphostin RG14620 is a potent and selective modulator of ABCG2 that may be useful to overcome chemoresistance in patients with drug-resistant tumors.