Regulatory T Cells in Peripheral Blood, Lymph Node, and Thyroid Tissue in Patients with Medullary Thyroid Carcinoma

Medullary Thyroid Cancer: Molecular Drivers and Immune Cellular Milieu of the Tumour Microenvironment-Implications for Systemic Treatment

In this review, we explore the underlying molecular biology of medullary thyroid carcinoma (MTC) and its interplay with the host immune system. MTC is consistently driven by a small number of specific pathogenic variants, beyond which few additional genetic events are required for tumorigenesis. This explains the exceedingly low tumour mutational burden seen in most MTC, in contrast to other cancers. However, because of the low tumour mutational burden (TMB), there is a correspondingly low level of tumour-associated neoantigens that are presented to the host immune system. This reduces tumour visibility and vigour of the anti-tumour immune response and suggests the efficacy of immunotherapy in MTC is likely to be poor, acknowledging this inference is largely based on the extrapolation of data from other tumour types. The dominance of specific RET (REarranged during Transfection) pathogenic variants in MTC tumorigenesis rationalizes the observed efficacy of the targeted RET-specific tyrosine kinase inhibitors (TKIs) in comparison to multi-kinase inhibitors (MKIs). Therapeutic durability of pathway inhibitors is an ongoing research focus. It may be limited by the selection pressure TKI treatment creates, promoting survival of resistant tumour cell clones that can escape pathway inhibition through binding-site mutations, activation of alternate pathways, and modulation of the cellular and cytokine milieu of the tumour microenvironment (TME).

Epigenetic Alteration and its Association With Downregulated FOXP3 Gene in Indian Breast Cancer Patients

Background:FOXP3 gene, known to be a potential tumor suppressor, has been identified to interact with HER2 in mammary cancer. Moreover, the high expression of FOXP3 serves as a good predictor of the survival of patients in breast cancer, prostate cancer, and gastric cancer. The expression and epigenetic alterations were evaluated in female breast cancer patients.

Material and Methods: Expression studies at the mRNA level and protein level were conducted in 140 breast cancer cases by real-time PCR and immunohistochemistry, respectively. Epigenetic studies were also conducted by analyzing the methylation status at the promoter region of the gene using MS-PCR.

Results:FOXP3 mRNA expression and protein expression were downregulated in breast cancer patients. The absence of FOXP3 protein expression is significantly associated with promoter methylation, where 70 methylated cases exhibited protein loss (70/95, 73.6%). Statistically, we also found a significant correlation between FOXP3 protein expression and TNM stage, promoter methylation, and histological grade. The methylated FOXP3 cases that did not express protein were also significantly associated with positive lymph node metastasis and HER-2 status.

Conclusion: The expression profile of FOXP3 may serve as a prognostic factor. In short, FOXP3 may stand in the most crucial list of biomarkers for breast cancer, bringing compelling results in terms of treatment and management of the disease.

A Case Report of Sequential Use of a Yeast-CEA Therapeutic Cancer Vaccine and Anti-PD-L1 Inhibitor in Metastatic Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) accounts for ~4% of all thyroid malignancies. MTC derives from the neural crest and secretes calcitonin (CTN) and carcinoembryonic antigen (CEA). Unlike differentiated thyroid cancer, MTC does not uptake iodine and I-131 RAI (radioactive iodine) treatment is ineffective. Patients with metastatic disease are candidates for FDA-approved agents with either vandetanib or cabozantinib; however, adverse effects limit their use. There are ongoing trials exploring the role of less toxic immunotherapies in patients with MTC. We present a 61-year-old male with the diagnosis of MTC and persistent local recurrence despite multiple surgeries. He was started on sunitinib, but ultimately its use was limited by toxicity. He then presented to the National Cancer Institute (NCI) and was enrolled on a clinical trial with heat-killed yeast-CEA vaccine (NCT01856920) and his calcitonin doubling time improved in 3 months. He then came off vaccine for elective surgery. After surgery, his calcitonin was rising and he enrolled on a phase I trial of avelumab, a programmed death-ligand 1 (PD-L1) inhibitor (NCT01772004). Thereafter, his calcitonin decreased > 40% on 5 consecutive evaluations. His tumor was subsequently found to express PD-L1. CEA-specific T cells were increased following vaccination, and a number of potential immune-enhancing changes were noted in the peripheral immunome over the course of sequential immunotherapy treatment. Although calcitonin declines do not always directly correlate with clinical responses, this response is noteworthy and highlights the potential for immunotherapy or sequential immunotherapy in metastatic or unresectable MTC.

RET-mediated modulation of tumor microenvironment and immune response in multiple endocrine neoplasia type 2 (MEN2)

Medullary thyroid carcinomas (MTC) arise from thyroid parafollicular, calcitonin-producing C-cells and can occur either as sporadic or as hereditary diseases in the context of familial syndromes, including multiple endocrine neoplasia 2A (MEN2A), multiple endocrine neoplasia 2B (MEN2B) and familial MTC (FMTC). In a large fraction of sporadic cases, and virtually in all inherited cases of MTC, activating point mutations of the RET proto-oncogene are found. RET encodes for a receptor tyrosine kinase protein endowed with transforming potential on thyroid parafollicular cells. As in other cancer types, microenvironmental factors play a critical role in MTC. Tumor-associated extracellular matrix, stromal cells and immune cells interact and influence the behavior of cancer cells both in a tumor-promoting and in a tumor-suppressing manner. Several studies have shown that, besides the neoplastic transformation of thyroid C-cells, a profound modification of tumor microenvironment has been associated to the RET FMTC/MEN2-associated oncoproteins. They influence the surrounding stroma, activating cancer-associated fibroblasts (CAFs), promoting cancer-associated inflammation and suppressing anti-cancer immune response. These mechanisms might be exploited to develop innovative anti-cancer therapies and novel prognostic tools in the context of familial, RET-associated MTC.

Leveraging the immune system to treat advanced thyroid cancers

Inflammation has long been associated with the thyroid and with thyroid cancers, raising seminal questions about the role of the immune system in the pathogenesis of advanced thyroid cancers. With a growing understanding of dynamic tumour-immune cell interactions and the mechanisms by which tumour cells evade antitumour immunity, the field of cancer immunotherapy has been revolutionised. In this Review, we provide evidence to support the presence of an antitumour immune response in advanced thyroid cancers linked to cytotoxic T cells and NK cells. This antitumour response, however, is likely blunted by the presence of immunosuppressive pathways within the microenvironment, facilitated by tumour-associated macrophages or increased expression of negative regulators of cytotoxic T-cell function. Current and future efforts to incorporate immune-based therapies into existing tumour cell or endothelial-derived therapies-eg, with kinase inhibitors targeting tumour-associated macrophages or antibodies blocking negative regulators on T cells-could provide improved and durable responses for patients with disease that is otherwise refractory to treatment.

Inhibition of Foxp3 in cancer cells induces apoptosis of thyroid cancer cells

Foxp3+ regulatory T cells (Tregs) in lymphocytes facilitate the thyroid tumor growth and invasion. Very limited information is available on Foxp3 expression in thyroid cancer cells and its function is totally unknown. This study demonstrated that Foxp3 expression was increased in thyroid cancer cells. Inhibition of Foxp3 decreased cell proliferation and migration, but increased apoptosis, suggesting a positive role of Foxp3 in cancer growth. Interestingly, Foxp3 inhibition enhanced PPARγ expression and activity. In addition, Foxp3 inhibition downregulated NF-κB subunit p65 and cyclin D1 but upregulated caspase-3 levels. These molecular changes are in line with Foxp3 shRNA-mediated alteration of cell functions. Collectively, our study demonstrates that thyroid cancer cells express a high level of functional Foxp3 and that the inhibition of the Foxp3 suppresses the proliferation and migration but promotes apoptosis, suggesting that targeting Foxp3 in thyroid cancer cells may offer a novel therapeutic option for thyroid cancer.

Immune response in thyroid cancer: widening the boundaries

The association between thyroid cancer and thyroid inflammation has been repeatedly reported and highly debated in the literature. In fact, both molecular and epidemiological data suggest that these diseases are closely related and this association reinforces that the immune system is important for thyroid cancer progression. Innate immunity is the first line of defensive response. Unlike innate immune responses, adaptive responses are highly specific to the particular antigen that induced them. Both branches of the immune system may interact in antitumor immune response. Major effector cells of the immune system that directly target thyroid cancer cells include dendritic cells, macrophages, polymorphonuclear leukocytes, mast cells, and lymphocytes. A mixture of immune cells may infiltrate thyroid cancer microenvironment and the balance of protumor and antitumor activity of these cells may be associated with prognosis. Herein, we describe some evidences that immune response may be important for thyroid cancer progression and may help us identify more aggressive tumors, sparing the vast majority of patients from costly unnecessary invasive procedures. The future trend in thyroid cancer is an individualized therapy.

The role of E3 ubiquitin ligase Cbl proteins in interleukin-2-induced Jurkat T-cell activation

Interleukin- (IL-) 2 is the major growth factor for T-cell activation and proliferation. IL-2 has multiple functions in the regulation of immunological processes. Although most studies focus on T-cell immunomodulation, T-cell activation by IL-2 is the foundation of priming the feedback loop. Here, we investigated the effect of MAPK/ERK and PI3K/Akt signaling pathways on IL-2-induced cell activation and the regulatory mechanisms of upstream ubiquitin ligase Cbl-b and c-Cbl. Morphological analysis of Jurkat T cells was performed by cytospin preparations with Wright-Giemsa stain. CD25 expression on Jurkat T cells was determined by flow cytometry. Changes in cell activation proteins such as p-ERK, ERK, p-Akt, Akt, and ubiquitin ligase Casitas B-cell Lymphoma (Cbl) proteins were analyzed by western blot. Following IL-2-induced activation of Jurkat T cells, p-ERK expression was upregulated, while there was no change in p-Akt, ERK, or Akt expression. Thus, the MAPK/ERK signaling pathway, but not PI3K/Akt, was involved in IL-2-induced T-cell activation. Either using PD98059 (a specific inhibitor for p-ERK) or depletion of ERK with small interfering RNA (siRNA) reduced the expression of CD25. This study also showed that ubiquitin ligase proteins Cbl-b and c-Cbl might be involved in IL-2-induced Jurkat T-cell activation by negatively regulating the MAPK/ERK signaling pathway.

Circulating regulatory T cells of cancer patients receiving radiochemotherapy may be useful to individualize cancer treatment

BACKGROUND AND PURPOSE

Dendritic cells (DCs) and regulatory T cells (Treg) play a major role in anti-tumor immune response of cancer patients. We investigated the effect of radiochemotherapy on patients' blood immune cells and their predictive value for tumor response.

MATERIALS AND METHODS

DCs and Treg of colorectal cancer (CRC) or breast cancer (BC) patients were examined through multicolor flow cytometry before the beginning and after the first week of radiochemotherapy (RCT). DCs were stained for BDCA1 and BDCA2, Treg were stained for CD4, CD25, CD127 and FoxP3. IL-2, IL-10 and TNF-α plasma levels of CRC patients were also determined. We examined the interrelationship between immune cell count alterations, applied dose values, cytokine plasma levels as well as histopathological parameters.

RESULTS

DCs were increased in BC and CRC patients compared to healthy control individuals (HC). CRC patients had higher levels of Treg (59.0%) compared to BC patients (31.3%) and HC (27.0%). Treg of CRC (58.7% vs. 41.3% p<0.001) but not BC patients (31.3% vs. 38.8%, p=0.164) decreased distinctly after the first week of radiation therapy. Applied dose values and decrease of Treg correlated positively (r=0.216, p=0.054). We also found a positive correlation of IL-10 plasma levels and Treg levels (r=0.748, p=0.021). CRC patients with favorable tumor stage (<ypT3a) have higher levels of Treg after 5 days of RCT (49.4% vs. 34.0%, p=0.043).

CONCLUSION

Higher Treg levels are associated with favorable tumor stage. We hypothesize that a dramatic decrease of Treg after in vivo irradiation may be a good indicator for necessary dose adjustments in radiation therapy of CRC patients.