Elevated expression of nuclear protein kinase CK2α as a poor prognosis indicator in lymph node cancerous metastases of human thyroid cancers

Protein kinase CK2 – diverse roles in cancer cell biology and therapeutic promise

The association of protein kinase CK2 (formerly casein kinase II or 2) with cell growth and proliferation in cells was apparent at early stages of its investigation. A cancer-specific role for CK2 remained unclear until it was determined that CK2 was also a potent suppressor of cell death (apoptosis); the latter characteristic differentiated its function in normal versus malignant cells because dysregulation of both cell growth and cell death is a universal feature of cancer cells. Over time, it became evident that CK2 exerts its influence on a diverse range of cell functions in normal as well as in transformed cells. As such, CK2 and its substrates are localized in various compartments of the cell. The dysregulation of CK2 is documented in a wide range of malignancies; notably, by increased CK2 protein and activity levels with relatively moderate change in its RNA abundance. High levels of CK2 are associated with poor prognosis in multiple cancer types, and CK2 is a target for active research and testing for cancer therapy. Aspects of CK2 cellular roles and targeting in cancer are discussed in the present review, with focus on nuclear and mitochondrial functions and prostate, breast and head and neck malignancies.

CK2α causes stemness and chemotherapy resistance in liver cancer through the Hedgehog signaling pathway

BACKGROUND

Liver cancer is one of the major causes of cancer-related deaths globally. Cancer cell stemness and chemotherapy resistance contribute to the high mortality. Although evidence indicates that the alpha subunit of protein kinase 2 (CK2α) is involved in several human cancers, its function in liver cancer remains unknown. In the present study, we aimed to elucidate the role of CK2α in liver cancer.

METHODS

We examined the role of CK2α regulation in stemness and chemotherapy resistance capacity of liver cancer cells. MTT assays, tumor sphere formation assays, RT-PCR, flow cytometry, Western blotting assay, clonogenicity assay, matrigel invasion assay and bioinformatics were conducted in this study.

RESULTS

CK2α expression in the liver cancer tissues was notably upregulated compared with that in the corresponding non-tumorous tissues. The overexpression of CK2α promoted tumor sphere formation, increased the percentage of CD133(+) and side population cells, caused the resistance of liver cancer cells to 5-FU treatment, increased the expression levels of NANOG, OCT4, SOX2, Gli1 and Ptch1, and enhanced the ability of CD133(+) cell clone formation and invasion. Consistently, the downregulation of CK2α had the opposite effects. CK2α silencing inhibited the Hedgehog pathway by reducing the expression of Gli1 and Ptch1. Mechanistically, CK2α regulation on liver cancer cell stemness and chemotherapy resistance was found to be involved in the Hedgehog signaling pathway.

CONCLUSIONS

Our study may bring some new insights into the occurrence of liver cancer. Furthermore, these findings suggest that targeting CK2α may be a novel therapeutic strategy for patients with liver cancer.

Increased Expression of GARP in Papillary Thyroid Carcinoma

Regulatory T cells (Tregs) are immunosuppressive immune cells that play an important role in tumor development. Suppression of Treg function is considered to be an effective strategy for cancer therapy. Glycoprotein A repetitions predominant (GARP) has been found on the surface of activated Tregs. GARP has been recently observed in only a few solid tumors including breast, colon, lung cancers, and melanoma. However, its function in cancers remains unknown. Here, we investigated the expression of GARP in human papillary thyroid carcinoma (PTC) and its prognostic significance. In this study, immunohistochemistry was performed to examine the expression of GARP and Foxp3 in 19 human PTC tissues (including 10 cases with and 9 cases without lymph node metastasis) and 20 benign thyroid diseases (including 10 cases with nodular goiter and 10 cases with adenoma). Compared with benign thyroid diseases, we found a significant increase in the expression of GARP in PTC. Increased GARP expression in PTC was positively correlated with increased expression of Foxp3, which is very important for development of Tregs. But, there is no significant association of elevated expression of GARP with lymph node metastasis in PTC. Our results indicate that GARP is implicated in the development of PTC and might be a potential novel target for anticancer therapy. In addition, our findings further support the existence of a positive-feedback loop between GARP and Foxp3.

Cancer-type dependent expression of CK2 transcripts

A multitude of proteins are aberrantly expressed in cancer cells, including the oncogenic serine-threonine kinase CK2. In a previous report, we found increases in CK2 transcript expression that could explain the increased CK2 protein levels found in tumors from lung and bronchus, prostate, breast, colon and rectum, ovarian and pancreatic cancers. We also found that, contrary to the current notions about CK2, some CK2 transcripts were downregulated in several cancers. Here, we investigate all other cancers using Oncomine to determine whether they also display significant CK2 transcript dysregulation. As anticipated from our previous analysis, we found cancers with all CK2 transcripts upregulated (e.g. cervical), and cancers where there was a combination of upregulation and/or downregulation of the CK2 transcripts (e.g. sarcoma). Unexpectedly, we found some cancers with significant downregulation of all CK2 transcripts (e.g. testicular cancer). We also found that, in some cases, CK2 transcript levels were already dysregulated in benign lesions (e.g. Barrett’s esophagus). We also found that CK2 transcript upregulation correlated with lower patient survival in most cases where data was significant. However, there were two cancer types, glioblastoma and renal cell carcinoma, where CK2 transcript upregulation correlated with higher survival. Overall, these data show that the expression levels of CK2 genes is highly variable in cancers and can lead to different patient outcomes.

Stromal modulation and its role in the diagnosis of papillary patterned thyroid lesions

The papillary patterned lesion of thyroid may be challenging with many diagnostic pitfalls. Tumor stroma plays an important part in the determination of the tumor phenotype. CD34 is thought to be involved in the modulation of cell adhesion and signal transduction as CD34(+) fibrocytes are potent antigen-presenting cells. Smooth muscle actin (SMA) positivity could be diagnostic for fibroblast activation during tumorigenesis. We aimed to examine the expression of CD34 and alphaSMA in the stroma of papillary thyroid hyperplasia, papillary thyroid carcinoma and papillary tumors of uncertain malignant potential in order to elucidate their possible differential distribution and roles. A total number of 54 cases with papillary thyroid lesions were studied by routine HandE staining, CD34 and ASMA immunostaining. ASMA was not expressed in benign papillary hyperplastic lesions while it was expressed in papillary carcinoma, indicating that tumors have modulated stroma. Although the stroma was not well developed in papillary lesions with equivocal features of uncertain potentiality, CD34 was notable in such cases with higher incidence in malignant cases. So ASMA as well as CD34 could predict neoplastic behavior, pointing to the importance of the stromal role. Differences between groups suggest that the presence of CD34 + stromal cells is an early event in carcinogensis and is associated with neoplasia, however ASMA+ cells are more likely to be associated with malignant behavior and metastatic potential adding additional tools to the light microscopic picture helping in diagnosis of problematic cases with HandE.