Blockade of the programmed death ligand 1 (PD-L1) as potential therapy for anaplastic thyroid cancer

PD-L1 Expression and Its Modulating Factors in Anaplastic Thyroid Carcinoma: A Multi-institutional Study

Anti-PD immunotherapy is currently under investigation in anaplastic thyroid carcinoma (ATC). Tumor cell surface PD-L1 expression is considered predictive of therapeutic response. Although papillary thyroid carcinoma has been widely studied for PD-L1 expression, there are limited data on ATC. In this retrospective multi-institutional study involving 9 centers across Asia, 179 ATCs were assessed for PD-L1 expression using the SP263 (Ventana) clone. A tumor proportion score (TPS) ≥1% was required to consider a case PD-L1-positive. PD-L1 expression was compared with the histological patterns, the type of specimen (small or large), tumor molecular profile ( BRAF V600E and TERT promoter mutation status), and patient outcome. PD-L1 expression in any co-existent differentiated thyroid carcinoma (DTC) was evaluated separately and compared with ATC. Most ATCs (73.2%) were PD-L1-positive. The median TPS among positive cases was 36% (IQR 11% to 75%; range 1% to 99%). A high expression (TPS ≥ 50%) was noted in 30.7%. PD-L1-negative cases were more likely to be small specimens ( P =0.01). A negative result on small samples, hence, may not preclude expression elsewhere. ATCs having epithelioid and pleomorphic histological patterns were more likely to be PD-L1-positive with higher TPS than sarcomatoid ( P <0.01). DTCs were more frequently negative and had lower TPS than ATC ( P <0.01). Such PD-L1 conversion from DTC-negative to ATC-positive was documented in 71% of cases with co-existent DTC. BRAF V600E, but not TERT promoter mutations, correlated significantly with PD-L1-positivity rate ( P =0.039), reinforcing the potential of combining anti-PD and anti-BRAF V600E drugs. PD-L1 expression, however, did not impact the patient outcome.

Evaluation of CTLA-4 and PD-L1 Expression in Thyroid Carcinoma and Its Prognostic Significance

Introduction Immune checkpoint inhibitors (ICIs) targeting cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed death-ligand 1 (PD-L1) have revolutionised treatment and improved outcomes in various malignancies. We aimed to evaluate CTLA-4 and PD-L1 immunoexpression in thyroid tumours and correlated them with clinicopathological parameters. Methods The study included 90 cases of thyroid malignancies comprising papillary thyroid carcinoma (PTC) (n = 64, 54.2%), follicular thyroid carcinoma (FTC) (n = 19, 16.1%), anaplastic thyroid carcinoma (ATC) (n = 3, 2.5%), and poorly differentiated carcinoma (n = 4, 3.4%), two cases (1.69%) of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) along with 26 cases (22%) of benign thyroid lesions. CTLA-4 (UMAB249) and PD-L1 (SP263) expression were assessed in all the cases of thyroid tumours. Results were compared with clinicopathologic parameters and overall survival. Results PD-L1 was positive in all three cases of anaplastic thyroid carcinoma (ATC), 33% (n = 21) cases of PTC, and 16% (n = 3) cases of FTC. PD-L1 positivity was significantly associated at tumour proportion score (TPS) ≥1% with lymphovascular invasion and age ≤40 years and at TPS ≥50% with tumour necrosis and N-stage. Immune proportion score (IPS) did not correlate with any clinicopathological parameters except for the N-stage. CTLA-4 was positive in six cases of PTC (1-5%); five showed lymph node involvement (p = 0.032). IPS was positive in 14 cases, and a significant association was seen with lymph node metastasis, lymphocytic infiltration, and lymphovascular invasion. Three cases of PTC showed co-expression for PD-L1 and CTLA-4 in tumour cells. No significant association was seen between PD-L1 expression and survival. Conclusion The current data suggest that PD-L1 is expressed in differentiated thyroid carcinoma, mainly PTC and ATC, indicating higher responsiveness to immunotherapy. A subset of PTC showed co-expression of PD-L1 and CTLA-4. These findings suggest the need for further investigation to utilise combinational immunotherapy, including anti-PD-L1 and anti-CTLA-4.

Nearly Half of Patients with Anaplastic Thyroid Cancer May Be Amenable to Immunotherapy

IMPORTANCE

Poorly differentiated cancer (PDC) and anaplastic thyroid cancer (ATC) have an aggressive course of disease with limited treatment options. The expression of programmed cell death ligand-1 (PD-L1) has been used to determine the responses of many cancers to immunotherapy. The aim of the study was to investigate the expression of PD-L1 in a cohort of patients with PDC and ATC to assess their suitability for immunotherapy. Data, settings, and participants: This study is a retrospective cohort review of patients treated for PDC and ATC treated at a tertiary referral institution during the period 2000-2020. PD-L1 22C3 pharmDx qualitative immunohistochemistry was performed on formalin-fixed, paraffin-embedded (FFPE) specimens of tumours to detect the presence of the PD-L1 protein.

MAIN OUTCOME MEASURES

The percentage of tumours that were positive for PD-L1 immunohistochemistry and the PD-L1 protein expression as measured by using the Tumour Proportion Score (TPS). Secondary outcomes studied were the associations between demographic, clinicopathological, treatment and disease outcomes and PD-L1 expression.

RESULTS

Nineteen patients (12F:7M) with a mean age of 65.4 (±14.3 SD) years were diagnosed with PDC in 4 (21%) and fifteen were diagnosed with ATC (79%) during the study period. Fifteen (79%) patients underwent some form of surgery, with R0 resection achieved in only three of the fifteen (20%) patients. Overall, PD-L1 expression was seen in seven of the fifteen (47%) of the patients with ATC, with no positivity seen in the patients with PDC. PD-L1 expression had no impact on treatment modality and positive expression was not significantly associated with stage of disease, metastasis, or survival.

CONCLUSION

Nearly half of patients with ATC express PD-L1 and may be amenable to immunotherapy with pembrolizumab.

Recent Trends and Potential of Radiotherapy in the Treatment of Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is a rare but highly aggressive malignancy characterized by advanced disease at diagnosis and a poor prognosis. Despite multimodal therapeutic approaches that include surgery, radiotherapy, and chemotherapy, an optimal treatment strategy remains elusive. Current developments in targeted therapies and immunotherapy offer promising avenues for improved outcomes, particularly for BRAF-mutant patients. However, challenges remain regarding overcoming drug resistance and developing effective treatments for BRAF-wild-type tumors. This comprehensive review examines the clinical and biological features of ATC, outlines the current standards of care, and discusses recent developments with a focus on the evolving role of radiotherapy. Moreover, it emphasizes the necessity of a multidisciplinary approach and highlights the urgent need for further research to better understand ATC pathogenesis and identify new therapeutic targets. Collaborative efforts, including large-scale clinical trials, are essential for translating these findings into improved patient outcomes.

Fucoidan MF4 from Fucus vesiculosus inhibits Lewis lung cancer via STING-TBK1-IRF3 pathway

Fucoidan, a sulfated polysaccharide of marine origin found in brown algae and sea cucumbers, has been identified as a neuroprotective compound. In this study, a novel fucoidan MF4 was extracted from Fucus vesiculosus and isolated using Q-Sepharose fast-flow ion-exchange chromatography. The physicochemical properties of MF4 were characterized. MF4 is primarily composed of fucose, xylose, galactose, glucose, and mannose in a molar ratio of 12.3: 4.9: 1.1: 1.0: 1.1, with an average molecular weight of 67.7 kDa. Notably, MF4 demonstrated suppression of LLC tumor growth in vivo. RNA-sequencing analysis revealed that MF4 enhanced the expression of type I interferon-associated downstream genes in macrophages. Furthermore, MF4 increased the levels of phosphorylated TBK1 and IRF3 proteins in vitro. By activating the STING-TBK1-IRF3 signaling pathway, MF4 may enhance the antitumor activity of macrophages. Taken together, MF4 has promising potential as an antitumor and immunomodulatory agent.

Progress in long non-coding RNAs as prognostic factors of papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is generally recognized as a slow-growing tumor. However, a small subset of patients may still experience relapse or metastasis shortly after therapy, leading to a poor prognosis and raising concerns about excessive medical treatment. One major challenge lies in the inadequacy of effective biomarkers for accurate risk stratification. Long non-coding RNAs (lncRNAs), which are closely related to malignant characteristics and poor prognosis, play a significant role in the genesis and development of PTC through various pathways. The objective of this review is to provide a comprehensive summary of the biological functions of lncRNAs in PTC, identify prognosis-relevant lncRNAs, and explore their potential mechanisms in drug resistance to BRAF kinase inhibitors, tumor dedifferentiation, and lymph node metastasis. By doing so, this review aims to offer valuable references for both basic research and the prediction of PTC prognosis.

[Personalized approach to anaplastic thyroid carcinoma]

BACKGROUND

Anaplastic thyroid carcinoma (ATC) represents the rarest but most aggressive tumor entity of the thyroid gland. In this respect, the treatment of advanced ATC has rapidly evolved in recent years. Recently, new personalized forms of treatment that address the somatic mutational status of the tumor have been increasingly used. The aim of this article is to provide an overview of current molecular-based and personalized treatment options for ATC.

METHODS

A current literature search was performed with a focus on personalized molecular-based treatment options for ATC.

RESULTS

The majority of patients suffering from ATC have an advanced tumor disease at the time of initial diagnosis. Despite multimodal treatment approaches consisting of surgery, external beam radiation therapy (EBRT) and chemotherapy (CTX), the prognosis of ATC is still poor. Accordingly, the focus of innovative treatment approaches is on molecular-based, individualized tumor therapy, including in particular BRAFV600E and multikinase inhibitors. The potential of the latter seems to lie particularly in combination therapy with immune checkpoint inhibitors. These treatment options can be used in both adjuvant and neoadjuvant settings. Neoadjuvant treatment of advanced ATC can achieve a potentially resectable treatment setting and improve the poor prognosis of affected patients; however, larger prospective and randomized studies on these combination therapies are currently pending.

CONCLUSION

The focus of future treatment approaches for ATC will be on individualized, molecular-based tumor therapy. In particular, the neoadjuvant use of these therapies may change the paradigm of ATC surgery as locally advanced as well as metastatic carcinomas can be converted to a potentially resectable status and made amenable to surgery.

Advances in the management of anaplastic thyroid carcinoma: transforming a life-threatening condition into a potentially treatable disease

Anaplastic thyroid cancer (ATC) is an infrequent thyroid tumor that usually occurs in elderly patients. There is often a history of previous differentiated thyroid cancer suggesting a biological progression. It is clinically characterized by a locally invasive cervical mass of rapid onset. Metastases are found at diagnosis in 50% of patients. Due to its adverse prognosis, a prompt diagnosis is crucial. In patients with unresectable or metastatic disease, multimodal therapy (chemotherapy and external beam radiotherapy) has yielded poor outcomes with 12-month overall survival of less than 20%. Recently, significant progress has been made in understanding the oncogenic pathways of ATC, leading to the identification of BRAF V600E mutations as the driver oncogene in nearly 40% of cases. The combination of the BRAF inhibitor dabrafenib (D) and MEK inhibitor trametinib (T) showed outstanding response rates in BRAF-mutated ATC and is now considered the standard of care in this setting. Recently, it was shown that neoadjuvant use of DT followed by surgery achieved 24-month overall survival rates of 80%. Although these approaches have changed the management of ATC, effective therapies are still needed for patients with BRAF wild-type ATC, and high-quality evidence is lacking for most aspects of this neoplasia. Additionally, in real-world settings, timely access to multidisciplinary care, molecular testing, and targeted therapies continues to be a challenge. Health policies are warranted to ensure specialized treatment for ATC.The expanding knowledge of ATC´s molecular biology, in addition to the ongoing clinical trials provides hope for the development of further therapeutic options.

Anti-Proliferative Effect of Radiotherapy and Implication of Immunotherapy in Anaplastic Thyroid Cancer Cells

Radiotherapy and immunotherapy have shown promising efficacy for the treatment of solid malignancies. Here, we aim to clarify the potential of a combined application of radiotherapy and programmed cell death-ligand 1 (PD-L1) monoclonal antibody atezolizumab in primary anaplastic thyroid cancer (ATC) cells. The radiation caused a significant reduction in cell proliferation, measured by luminescence, and of the number of colonies. The addition of atezolizumab caused a further reduction in cell proliferation of the irradiated ATC cells. However, the combined treatment did not cause either the exposure of the phosphatidylserine or the necrosis, assessed by luminescence/fluorescence. Additionally, a reduction in both uncleaved and cleaved forms of caspases 8 and 3 proteins was detectable in radiated cells. The DNA damage evidenced the over-expression of TP53, CDKN1A and CDKN1B transcripts detected by RT-qPCR and the increase in the protein level of P-γH2AX and the DNA repair deputed kinases. PD-L1 protein level increased in ATC cells after radiation. Radiotherapy caused the reduction in cell viability and an increase of PD-L1-expression, but not apoptotic cell death in ATC cells. The further combination with the immunotherapeutic atezolizumab could increase the efficacy of radiotherapy in terms of reduction in cell proliferation. Further analysis of the involvement of alternative cell death mechanisms is necessary to clarify their cell demise mechanism of action. Their efficacy represents a promising therapy for patients affected by ATC.

Radiotherapy combined with immunotherapy successfully treated one case of anaplastic thyroid cancer: A case report

Background

Anaplastic thyroid cancer (ATC) is a rare but highly fatal form of thyroid cancer. This highly malignant tumor progresses rapidly and is prone to relapse and metastasis, with a poor prognosis. Novel treatments have improved survival in recent years, but the outcome of treatment is not satisfactory.

Case presentation

We report a case of multiple postoperative recurrences of papillary thyroid carcinoma that later transformed into undifferentiated carcinoma. The patient's neck mass was huge and the operation was unsuitable. Then, she achieved remarkable tumor shrinkage by tislelizumab immunotherapy combined with radiotherapy.

Conclusion

This case indicates that radiotherapy combined with immunotherapy is a promising treatment for ATC. Such a combined approach warrants further study.

Synergic Induction of Autophagic Cell Death in Anaplastic Thyroid Carcinoma

Anaplastic thyroid carcinoma (ATC) has poor prognosis, high mortality rate and lack of effective therapy. A synergic combination of PD-L1 antibody together with cell death promoting substances like deacetylase inhibitors (DACi) and multi-kinase inhibitors (MKI) could sensitize ATC cells and promote decay by autophagic cell death. The PD-L1-inhibitor atezolizumab synergized with panobinostat (DACi) and sorafenib (MKI) leading to significant reduction of the viability, measured by real time luminescence, of three different patient-derived primary ATC cells, of C643 cells and follicular epithelial thyroid cells too. Solo administration of these compounds caused a significant over-expression of autophagy transcripts; meanwhile autophagy proteins were almost not detectable after the single administration of panobinostat, thus supporting a massive autophagy degradation process. Instead, the administration of atezolizumab caused an accumulation of autophagy proteins and the cleavage of the active caspases 8 and 3. Interestingly, only panobinostat and atezolizumab were able to exacerbate the autophagy process by increasing the synthesis, the maturation and final fusion with the lysosomes of the autophagosome vesicles. Despite ATC cells could be sensitized by atezolizumab via the cleavage of the caspases, no reduction of cell proliferation or promotion of cell death was observed. The apoptosis assay evidenced the ability of panobinostat alone and in combination with atezolizumab to induce the phosphatidil serine exposure (early apoptosis) and further the secondary necrosis. Instead, sorafenib was only able to cause necrosis. The increase of caspases activity induced by atezolizumab, the apoptosis and autophagy processes promoted by panobinostat synergize thus promoting cell death in well-established and primary anaplastic thyroid cancer cells. The combined therapy could represent a future clinical application for the treatment of such lethal and untreatable solid cancer.

Immunotherapy or targeted therapy: What will be the future treatment for anaplastic thyroid carcinoma?

Anaplastic thyroid carcinoma (ATC) is a rare and aggressive form of thyroid carcinoma (TC). Currently, there are no effective treatments for this condition. In the past few years, targeted therapy and immunotherapy have made significant progress in ATC treatment. Several common genetic mutations have been found in ATC cells, involving different molecular pathways related to tumor progression, and new therapies that act on these molecular pathways have been studied to improve the quality of life of these patients. In 2018, the FDA approved dabrafenib combined with trametinib to treat BRAF-positive ATC, confirming its therapeutic potential. At the same time, the recent emergence of immunotherapy has also attracted wide attention from researchers. While immunotherapy for ATC is still in the experimental stage, numerous studies have shown that immunotherapy is a potential therapy for ATC. In addition, it has also been found that the combination of immunotherapy and targeted therapy may enhance the anti-tumor effect of targeted therapy. In recent years, there has been some progress in the study of targeted therapy or immunotherapy combined with radiotherapy or chemotherapy, showing the prospect of combined therapy in ATC. In this review, we analyze the response mechanism and potential effects of targeted therapy, immunotherapy, and combination therapy in ATC treatment and explore the future of treatment for ATC.

Current picture of anaplastic thyroid cancer patients' care and meetable needs: A survey of 94 Institutions from the EORTC Endocrine and Head and Neck Cancer Groups

Anaplastic thyroid carcinoma (ATC) is a rare cancer accounting for 40% of thyroid cancer-specific deaths. In the last 5 years, improved insights into molecular pathways led the Food and Drug Administration to license BRAF/MEK inhibitors (B/Mi) in BRAF^V600E-mutant ATC, and pembrolizumab in solid cancer with high tumour mutational burden (TMB-H) (≥10 mutations/megabase) (mut/Mb). In Europe, clinicians face challenges in prescribing novel treatments, as the European Medical Association (EMA) has not licensed B/Mi nor immunotherapy (IO) for ATC so far. Some patients manage to receive these drugs through alternative ways. We investigated the extent of this phenomenon launching an online survey from March 12th to 19th 2021 open to 239 Institutions in the EORTC Endocrine and Head & Neck Cancer Groups. Questions enquired about the number of ATC patients evaluated/year, feasibility of BRAF assessment, accessibility to B/Mi-IO, availability of clinical trials and interest in new studies. Colleagues from 94 Institutions (20 Countries) joined: 30 centres evaluated ≥5 ATC patients/year, with an overall incidence >200 patients/year. 80.8% tested BRAF status, 43.6% by next-generation sequencing. 62.7% and 70% of responders reported limitations in prescribing B/Mi and IO, respectively: either the impossibility of offering them, or drugs accessibility exclusively under certain conditions (e.g. health insurance, clinical trials, compassionate use, off-label). Only 13.8% had clinical trials ongoing while 91.5% of sites claimed ATC-dedicated trials. Disparities in access to novel treatments are diffuse. Access to cutting-edge therapies is an urgent issue in this setting, and clinical trials seem feasible within an appropriate network.

Case report: Local cryoablation combined with pembrolizumab to eliminate lung metastases from ovarian clear cell carcinoma

Ovarian clear cell carcinoma has a high recurrence rate with poor prognosis and is generally not sensitive to conventional platinum-based chemotherapy. Its less frequent occurrence of mutations such as BRCA limited the targeted therapies. Immunotherapy is not currently recommended as a first-line agent for ovarian cancer, and most patients are not yet able to benefit from it. Cryoablation can be used to treat solid systemic tumors, including ovarian cancer metastases, and can produce a limited anti-tumor immune response. The anti-tumor effects of cryoablation combined with immunotherapy have not been adequately confirmed. This study reports a case of a patient with ovarian clear cell carcinoma who underwent conventional adjuvant chemotherapy after initially surgical resection of the tumor. Unfortunately, cancer recurred and metastasized to the abdominal wall. After a series of painful chemotherapy and a second surgery, the cancer was still not effectively controlled, and the patient developed extensive metastases in the lung. The patient’s PD-L1 expression level also did not support solo immunotherapy. We pioneered the use of cryoablation to first eradicate the most significant lesion in the upper lobe of the left lung and then combined it with the PD-L1 inhibitor pembrolizumab to treat the patient with immunotherapy, which resulted in the complete eradication of the other multiple metastases in the lung and saved the patient’s life. Although the precise mechanism of action has not yet been explored, we have reason to believe that the combination of cryoablation and immune checkpoint inhibitor has a powerful synergistic anti-tumor effect, which is yet to be confirmed by more basic research and clinical applications in the next step.

Evaluating new treatments for anaplastic thyroid cancer

INTRODUCTION

Anaplastic thyroid cancer (ATC) is one of the most lethal diseases known to humans with a median survival of 5 months. The American Thyroid Association (ATA) recently published guidelines for the treatment of this dreadful thyroid malignancy.

AREAS COVERED

This review presents the current therapeutic landscape of this challenging disease. We also present the results from trials published over the last five years and summarize currently active clinical trials.

EXPERT OPINION

Recent attempts to improve the prognosis of these tumors are moving toward personalized medicine, basing the treatment decision on the specific genetic profile of the individual tumor. The positive results of dabrafenib and trametinib for ATC harboring the BRAF V600E mutation have provided a useful treatment option. For the other genetic profiles, different drugs are available and can be used to individualize the treatment, likely using drug combinations. Combinations of drugs act on different molecular pathways and achieve inhibition at separate areas. With new targeted therapies, average survival has improved considerably and death from local disease progression or airway compromise is less likely with improvement in quality of life. Unfortunately, the results remain poor in terms of survival.

Rationale Efficacy and Safety Evidence of Lenvatinib and Pembrolizumab Association in Anaplastic Thyroid Carcinoma

Anaplastic thyroid carcinoma (ATC) are highly aggressive malignant tumors with poor overall prognosis despite multimodal therapy. As ATC are extremely rare, no randomized controlled study has been published for metastatic disease. Thyrosine kinase inhibitors, especially lenvatinib and immune checkpoint inhibitors such as pembrolizumab, are emerging drugs for ATC. Few studies have reported the efficacity of pembrolizumab and lenvatinib association, resulting in its frequent off-label use. In this review, we discuss rationale efficacy and safety evidence for the association of lenvatinib and pembrolizumab in ATC. First, we discuss preclinical rationale for pembrolizumab monotherapy, lenvatinib monotherapy and synergistic action of pembrolizumab and lenvatinib in the metastatic setting. We also discuss clinical evidence for immunotherapy and pembrolizumab in ATC through the analysis of studies evaluating immunotherapy, lenvatinib and pembrolizumab lenvatinib association in ATC. In addition, we discuss the safety of this association and potential predictive biomarkers of efficiency.

Immune Checkpoint Protein Expression Defines the Prognosis of Advanced Thyroid Carcinoma

BACKGROUND

Patients with advanced thyroid carcinoma (TC), such as anaplastic thyroid carcinoma (ATC), poorly differentiated thyroid carcinoma (PDTC), and locally advanced papillary thyroid carcinoma (PTC), have poor prognoses and require novel treatments. Immune checkpoint (ICP) inhibitors have demonstrated encouraging and good results; nevertheless, their effect in advanced TCs remains largely unclear. Thus, we demonstrated ICP profiles and investigated their potential clinical significance.

METHODS

A total of 234 TC patients were involved, with 22 ATCs, 44 PDTCs, and 168 PTCs, including 58 advanced PTCs. Immunohistochemistry was performed to evaluate nine ICPs [programmed cell death ligand 1 (PDL1), Programmed cell death 1 (PD1), cytotoxic T lymphocyte-associated protein 4 (CTLA4), B and T lymphocyte attenuator (BTLA), T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT), lymphocyte activation gene 3 (LAG3), V-domain immunoglobulin suppressor of T-cell activation (VISTA), B7 homolog 3 (B7-H3), and T-cell immunoglobulin and mucin domain- 3 protein (TIM3)] expression via tissue microarrays (TMAs), and clinical correlations were analyzed simultaneously.

RESULTS

ATC had the highest positive rate of ICPs among the three pathological types, as well as relatively high ICP co-expression. ATC with high expression of PDL1 positivity had a poor prognosis. Shorter survival was associated with VISTA, B7H3, TIM3, and TIGIT expression in PDTC. The greater the co-expression of these four ICPs, the poorer the prognosis in PDTC patients. VISTA and B7H3 were the two most commonly expressed ICPs in advanced PTC, both of which were linked to a poor prognosis.

CONCLUSIONS

PDL1 is linked to the overall survival (OS) of ATC. A subset of PDTC is likely immunogenic with poor prognosis and co-expression of VISTA, B7H3, TIM3, and TIGIT. Furthermore, VISTA and B7H3 are prognostic biomarkers in advanced PTC. Single or combined blockade targeting these ICPs might be effective for advanced TCs in the future.

What is the status of immunotherapy in thyroid neoplasms?

Immunotherapy has changed the treatment of patients with advanced cancer, with different phase III trials showing durable responses across different histologies. This review focuses on the preclinical and clinical evidence of potential predictive biomarkers of response and efficacy of immunotherapy in thyroid neoplasms. Programmed death-ligand 1 (PD-L1) staining by immunohistochemistry has shown higher expression in anaplastic thyroid cancer (ATC) compared to other subtypes. The tumor mutational burden in thyroid neoplasms is low but seems to be higher in ATC. Immune infiltrates in the tumor microenvironment (TME) differ between the different thyroid neoplasm subtypes. In general, differentiated thyroid cancer (DTC) has a higher number of tumor-associated lymphocytes and regulatory T cells (Tregs), while ATC and medullary thyroid cancer (MTC) display a high density of tumor-associated macrophages (TAMs). Nevertheless, results from clinical trials with immunotherapy as monotherapy or combinations have shown limited efficacy. Further investigation into new strategies aside from anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4)/programmed death 1 (PD-1)/PD-L1 antibodies, validation of predictive biomarkers, and better population selection for clinical trials in thyroid neoplasms is more than needed in the near future.

The prevalence of DNA microsatellite instability in anaplastic thyroid carcinoma - systematic review and discussion of current therapeutic options

INTRODUCTION

Anaplastic thyroid carcinoma is a rare, rapidly progressing, highly aggressive thyroid malignancy. Responses to immune checkpoint inhibitors in mismatch repair-deficient/microsatellite instability-high tumours of other locations have shown promising results, and with the extended approval of the PD-1 receptor inhibitor pembrolizumab by the Food and Drug Administration, also anaplastic thyroid cancer (ATC) requires analysis for microsatellite instability (MSI) status.

MATERIAL AND METHODS

Systematic research for relevant literature was conducted in different databases. Prevalence, detection methods, and the potential prognostic/predictive value of MSI in view of the available targeted therapies were of special focus.

RESULTS

Selected citations revealed the prevalence of MSI in 7.4%, with mutations in the MSH2 gene (33%) being the most frequent, followed by MSH6 (25%) and MLH1 (16.7%) occurring in the following combinations: MLH1-MSH2 (8.3%), MSH2-MSH6 (8.3%), and MLH3-MSH5 (8.3%). No mutations in the PMS2 gene were reported. Sixty-six co-mutations in 9 cases were found, with TP53 (88.9%), NF1 (44.4 %), ATM (33.3%), and RB1 (33.3%) being the most frequent. No RAS mutations were noted. Survival ranged between 2.8 and 48 months, and patient age varied between 49 and 84 years. There are insufficient and heterogenous data concerning the predictive or prognostic value of mismatch repair-deficient/microsatellite instability status.

CONCLUSIONS

Tumour molecular profiling is fundamental in ATC for predictive, prognostic, as well as therapeutic reasons, and analysis of MSI status is strongly suggested because a small subgroup show the MSI signature and might profit from recently approved targeted therapies.

Androgen Activity Is Associated With PD-L1 Downregulation in Thyroid Cancer

Thyroid cancer is the most prevalent endocrine malignancy in the United States with greater than 53,000 new cases in 2020. There is a significant gender disparity in disease incidence as well, with women developing thyroid cancer three times more often than men; however, the underlying cause of this disparity is poorly understood. Using RNA-sequencing, we profiled the immune landscape of papillary thyroid cancer (PTC) and identified a significant inverse correlation between androgen receptor (AR) levels and the immune checkpoint molecule PD-L1. The expression of PD-L1 was then measured in an androgen responsive-thyroid cancer cell line. Dihydrotestosterone (DHT) treatment resulted in significant reduction in surface PD-L1 expression in a time and dose-dependent manner. To determine if androgen-mediated PD-L1 downregulation was AR-dependent, we treated cells with flutamide, a selective AR antagonist, and prior to DHT treatment to pharmacologically inhibit AR-induced signaling. This resulted in a > 90% restoration of cell surface PD-L1 expression, suggesting a potential role for AR activity in PD-L1 regulation. Investigation into the AR binding sites showed AR activation impacts NF-kB signaling by increasing IkBα and by possibly preventing NF-kB translocation into the nucleus, reducing PD-L1 promoter activation. This study provides evidence of sex-hormone mediated regulation of immune checkpoint molecules in vitro with potential ramification for immunotherapies.

Combination of Lenvatinib and Pembrolizumab Is an Effective Treatment Option for Anaplastic and Poorly Differentiated Thyroid Carcinoma

Background: Anaplastic thyroid carcinoma (ATC) and metastatic poorly differentiated thyroid carcinomas (PDTCs) are rare aggressive malignancies with poor overall survival (OS) despite extensive multimodal therapy. These tumors are highly proliferative, with frequently increased tumor mutational burden (TMB) compared with differentiated thyroid carcinomas, and elevated programmed death ligand 1 (PD-L1) levels. These tumor properties implicate responsiveness to antiangiogenic and antiproliferative multikinase inhibitors such as lenvatinib, and immune checkpoint inhibitors such as pembrolizumab. Patients and Methods: In a retrospective study, we analyzed six patients with metastatic ATC and two patients with PDTC, who received a combination therapy of lenvatinib and pembrolizumab. Lenvatinib was started at 14-24 mg daily and combined with pembrolizumab at a fixed dose of 200 mg every three weeks. Maximum treatment duration with this combination was 40 months, and 3 of 6 ATC patients are still on therapy. Patient tumors were characterized by whole-exome sequencing and PD-L1 expression levels (tumor proportion score [TPS] 1-90%). Results: Best overall response (BOR) within ATCs was 66% complete remissions (4/6 CR), 16% stable disease (1/6 SD), and 16% progressive disease (1/6 PD). BOR within PDTCs was partial remission (PR 2/2). The median progression-free survival was 17.75 months for all patients, and 16.5 months for ATCs, with treatment durations ranging from 1 to 40 months (1, 4, 11, 15, 19, 25, 27, and 40 months). Grade III/IV toxicities developed in 4 of 8 patients, requiring dose reduction/discontinuation of lenvatinib. The median OS was 18.5 months, with three ATC patients being still alive without relapse (40, 27, and 19 months) despite metastatic disease at the time of treatment initiation (UICC and stage IVC). All patients with long-term (>2 years) or complete responses (CRs) had either increased TMB or a PD-L1 TPS >50%. Conclusions: Our results implicate that the combination of lenvatinib and pembrolizumab might be safe and effective in patients with ATC/PDTC and can result in complete and long-term remissions. The combination treatment is now being systematically examined in a phase II clinical trial (Anaplastic Thyroid Carcinoma Lenvatinib Pembrolizumab [ATLEP]) in ATC/PDTC patients.

PD-L1 expression and immune cells in anaplastic carcinoma and poorly differentiated carcinoma of the human thyroid gland: A retrospective study

Anaplastic thyroid carcinoma (ATC) and poorly differentiated thyroid carcinoma (PDTC) have limited treatment options, and immune profiling may help select patients for immunotherapy. The prevalence and relevance of programmed death-1 ligand (PD-L1) expression and the presence of immune cells in ATC and PDTC has not yet been well established. The present study investigated PD-L1 expression (clone 22C3) and cells in the tumor microenvironment (TME), including tumor-infiltrating lymphocytes (TILs), tumor-associated macrophages (TAMs) and dendritic cells, in whole tissue sections of 15 cases of ATC and 13 cases of PDTC. Immunohistochemical PD-L1 expression using a tumor proportion score (TPS) with a 1% cut-off was detected in 9/15 (60%) of ATC cases and 1/13 (7.7%) of PDTC cases (P=0.006). PD-L1 expression in TILs was limited to the ATC group (73.3 vs. 0% in ATC and PDTC, respectively). In the ATC group, the TPS for tumor positive PD-L1 expression revealed a non-significant trend towards worse survival, but no difference was observed when investigating PD-L1 expression in TILs and TAMs. In addition to increased PD-L1 expression, all ATC cases exhibited significantly increased CD3⁺ and CD8⁺ T cells, CD68⁺ and CD163⁺ macrophages, and S100⁺ dendritic cells compared with the PDTC cases. Loss of mutL homolog 1 and PMS1 homolog 2 expression was observed in one ATC case with the highest PD-L1 expression, as well as in the only PDTC case positive for PD-L1. Notably, the latter was the only PDTC case exhibiting positivity for p53 and a cellular microenvironment similar to ATC. The current results indicated that PD-L1 expression was frequent in ATC, but rare in PDTC. In addition to PD-L1, the present study suggested that microsatellite instability may serve a role in both the TME and the identification of immunotherapy candidates among patients with PDTC.

The Genomic Landscape of Thyroid Cancer Tumourigenesis and Implications for Immunotherapy

Thyroid cancer is the most prevalent endocrine malignancy that comprises mostly indolent differentiated cancers (DTCs) and less frequently aggressive poorly differentiated (PDTC) or anaplastic cancers (ATCs) with high mortality. Utilisation of next-generation sequencing (NGS) and advanced sequencing data analysis can aid in understanding the multi-step progression model in the development of thyroid cancers and their metastatic potential at a molecular level, promoting a targeted approach to further research and development of targeted treatment options including immunotherapy, especially for the aggressive variants. Tumour initiation and progression in thyroid cancer occurs through constitutional activation of the mitogen-activated protein kinase (MAPK) pathway through mutations in BRAF, RAS, mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway and/or receptor tyrosine kinase fusions/translocations, and other genetic aberrations acquired in a stepwise manner. This review provides a summary of the recent genetic aberrations implicated in the development and progression of thyroid cancer and implications for immunotherapy.

Anaplastic Thyroid Carcinoma: Current Issues in Genomics and Therapeutics

PURPOSE OF REVIEW

Anaplastic thyroid carcinoma is a type of thyroid carcinoma with the most aggressive biological behaviour amongst thyroid cancer. Here, we review the current genomic and the impacts of advances in therapies to improve the management of patients with the cancer.

RECENT FINDINGS

Common mutations being identified in anaplastic thyroid carcinoma are p53 and TERT promoter mutations. Other common mutated genes included BRAF, RAS, EIF1AX, PIK3CA, PTEN and AKT1, SWI/SNF, ALK and CDKN2A. Changes in expression of different microRNAs are also involved in the pathogenesis of anaplastic thyroid carcinoma. Curative resection combined with radiotherapy and combination chemotherapies (such as anthracyclines, platins and taxanes) has been shown to have effects in the treatment of some patients with anaplastic thyroid carcinoma. Newer molecular targeted therapies in clinical trials target mostly the cell membrane kinase and downstream proteins. These include targeting the EGFR, FGFR, VEGFR, c-kit, PDGFR and RET on the cell membrane as well as VEGF itself and the downstream targets such as BRAF, MEK and mTOR. Immunotherapy is also being tested in the cancer. Updated knowledge of genomic as well as clinical trials on novel therapies is needed to improve the management of the patients with this aggressive cancer.

LncRNA UCA1 attenuated the killing effect of cytotoxic CD8 + T cells on anaplastic thyroid carcinoma via miR-148a/PD-L1 pathway

BACKGROUND

LncRNAs play an important role in the regulation of the killing effect of cytotoxic CD8 + T cells in various cancers. However, the role and underlying mechanisms of UCA1 in the killing effect of cytotoxic CD8 + T cells in anaplastic thyroid carcinoma (ATC) are not clear.

METHODS

UCA1, miR-148a, and PD-L1 expression were detected by quantitative real-time PCR and/or Western blot. The ratio of PD-L1⁺ATC cells/ATC cells was determined using flow cytometry. The ability of CD8 + T cells to kill target ATC cells was detected by Chromium-51 (⁵¹Cr) release assay. The targeted relationship between UCA1 and miR-148a was confirmed by dual-luciferase reporter gene assay.

RESULTS

UCA1 and PD-L1 expression levels were elevated in ATC tissues and cells. Silencing UCA1 and PD-L1 enhanced the killing effect of cytotoxic CD8 + T cells on ATC cells. UCA1 negatively regulated the expression of miR-148a, and miR-148a targeted PD-L1 to down-regulate its expression. Besides, we found that UCA1 attenuated the killing effect of cytotoxic CD8 + T cells and reduced cytokine secretion through PD-L1 and miR-148a. Finally, silencing UCA1 or PD-L1 in ATC cells restored the suppression of the killing effect of CD8 + T cells in vivo.

CONCLUSION

UCA1 attenuated the killing effect of cytotoxic CD8 + T cells on ATC cells through the miR-148a/PD-L1 pathway.

Improvement of Overall Survival Using TKIs as Salvage Therapy in Advanced Thyroid Carcinoma: Real-Life Data on a Single Center Experience

Background: Tyrosine kinase inhibitors (TKIs) have improved progression-free survival in patients with advanced thyroid cancer. So far, few studies have investigated the efficacy of TKIs in a second-line setting. The purpose of our study was to explore the salvage therapy efficacy in patients with advanced thyroid cancer. Methods: We retrospectively evaluated 63 patients with progressive advanced thyroid carcinoma treated with TKIs divided into a Study group (23 patients) treated with salvage therapy, and a Control group (40 patients) treated with only one TKI. Results: Similar clinical benefits (stable disease + partial response) and progression free survival between the first and the second line TKI were observed in the Study group (p > 0.99 and p = 0.5, respectively). Median overall survival (OS) was 67.7 months in the Study group and 22.6 months in the Control group (HR 2.46; 95% CI 1.34–4.52, p = 0.004). After stratifying the whole population by age (<65 and ≥65 years), OS was significantly different (p < 0.001) with the best survival curve in younger patients, treated with salvage therapy and the worst in older subjects, treated with only one TKI. Conclusions: Salvage therapy showed a significant improvement of OS in patients with advanced thyroid cancer who experienced disease progression during prior TKI therapies.

A new risk factor indicator for papillary thyroid cancer based on immune infiltration

Increasing evidence has indicated a close association between immune infiltration in cancer and clinical outcomes. However, related research in thyroid cancer is still deficient. Our research comprehensively investigated the immune infiltration of thyroid cancer. Data derived from TCGA and GEO databases were analyzed by the CIBERSORT, ESTIMATE, and EPIC algorithms. The CIBERSORT algorithm calculates the proportions of 22 types of immune cells. ESTIMATE algorithm calculates a stromal score to represent all stromal cells in cancer. The EPIC algorithm calculates the proportions of cancer-associated fibroblasts (CAFs) and endothelial cells (ECs), which are the main components of stromal cells. We analyzed the correlation of immune infiltration with clinical characteristics and outcomes of patients. We determined that the infiltration of CD8⁺ T cells improved the survival of thyroid cancer patients. Overexpression of immune checkpoints was closely related to the development of thyroid cancer. In general, stromal cells were associated with the progression of thyroid cancer. Interestingly, CAFs and ECs had opposite roles in this process. In addition, the BRAF^V600E mutation was related to the upregulation of immune checkpoints and CAFs and the downregulation of CD8⁺ T cells and ECs. Finally, we constructed an immune risk score model to predict the prognosis and development of thyroid cancer. Our research demonstrated a comprehensive panorama of immune infiltration in thyroid cancer, which may provide potential value for immunotherapy.

From biomarkers to therapeutic targets: the promise of PD-L1 in thyroid autoimmunity and cancer

The programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) immune checkpoint proteins hold promise as diagnostic, prognostic, and therapeutic targets for precision oncology. By restoring antitumor T cell surveillance, the high degree of effectiveness of the immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment. However, the majority of patients (65-80 %) treated with ICIs experience significant side effects, called immune-related adverse events (irAEs), resulting in autoimmune damage to various organs. Therefore, broadening the clinical applicability of these treatments to all cancer types requires an improved understanding of the mechanisms linking cancer immune evasion and autoimmunity. The thyroid is the endocrine gland the most frequently involved in autoimmunity and cancer, the growing incidence of which is raising serious public health issues worldwide. In addition, the risk of developing thyroid cancer is increased in patients with autoimmune thyroid disease and thyroid dysfunction is one of the most common irAEs, especially with PD‑1/PD-L1 blockade. Therefore, we chose the thyroid as a model for the study of the link between autoimmunity, irAEs, and cancer. We provide an update into the current knowledge of the PD‑1/PD-L1 axis and discuss the growing interest of this axis in the diagnosis, prognosis, and management of thyroid diseases within the context of autoimmunity and cancer, while embracing personalized medicine.

Evolution of anaplastic thyroid cancer management: perspectives in the era of precision oncology

Anaplastic thyroid cancer is a rare aggressive malignancy resulting in poor outcomes, including significant morbidity and mortality. Historically, the overall survival of patients with anaplastic thyroid cancer has been less than 12 months. Multidisciplinary approaches combining surgery, radiation, and chemotherapy have been implemented to control this ominous disease. The evolution in science and technology has promoted deeper knowledge in the genetic pathways and mechanisms driving advance thyroid cancer. Furthermore, understanding molecular pathways resulted in the application of antineoplastic agents used in other tumors to thyroid cancer and the development of new highly selective drugs. A major landmark in anaplastic thyroid cancer management history was recently reached with the approval of BRAF and MEK inhibitor combination, specifically dabrafenib and trametinib for BRAF-mutated anaplastic thyroid cancer; this treatment has improved survival and outcomes in this population. Similarly, newer kinase inhibitors and immunotherapy are further shifting advanced thyroid cancer management to consider as first-line therapy inhibiting actionable oncogenic alterations. Therefore, newer treatment paradigms are incorporating molecular testing to provide personalized cancer care in anaplastic thyroid cancer. In this review, the principal aim is to provide an overview of the available international data on tyrosine kinase inhibitors and immunotherapy in the management of anaplastic thyroid cancer.

Novel Therapeutics in Radioactive Iodine-Resistant Thyroid Cancer

Iodine-resistant cancers account for the vast majority of thyroid related mortality and, until recently, there were limited therapeutic options. However, over the last decade our understanding of the molecular foundation of thyroid function and carcinogenesis has driven the development of many novel therapeutics. These include FDA approved tyrosine kinase inhibitors and small molecular inhibitors of VEGFR, BRAF, MEK, NTRK and RET, which collectively have significantly changed the prognostic outlook for this patient population. Some therapeutics can re-sensitize de-differentiated cancers to iodine, allowing for radioactive iodine treatment and improved disease control. Remarkably, there is now an FDA approved treatment for BRAF-mutated patients with anaplastic thyroid cancer, previously considered invariably and rapidly fatal. The treatment landscape for iodine-resistant thyroid cancer is changing rapidly with many new targets, therapeutics, clinical trials, and approved treatments. We provide an up-to-date review of novel therapeutic options in the treatment of iodine-resistant thyroid cancer.

Programmed death ligand-1 (PD-L1) as a predictive marker for immunotherapy in solid tumours: a guide to immunohistochemistry implementation and interpretation

Immunotherapy with checkpoint inhibitors is well established as an effective treatment for non-small cell lung cancer and melanoma. The list of approved indications for treatment with PD-1/PD-L1 checkpoint inhibitors is growing rapidly as clinical trials continue to show their efficacy in patients with a wide range of solid tumours. Clinical trials have used a variety of PD-L1 immunohistochemical assays to evaluate PD-L1 expression on tumour cells, immune cells or both as a potential biomarker to predict response to immunotherapy. Requests to pathologists for PD-L1 testing to guide choice of therapy are rapidly becoming commonplace. Thus, pathologists need to be aware of the different PD-L1 assays, methods of evaluation in different tumour types and the impact of the results on therapeutic decisions. This review discusses the key practical issues relating to the implementation of PD-L1 testing for solid tumours in a pathology laboratory, including evidence for PD-L1 testing, different assay types, the potential interchangeability of PD-L1 antibody clones and staining platforms, scoring criteria for PD-L1, validation, quality assurance, and pitfalls in PD-L1 assessment. This review also explores PD-L1 IHC in solid tumours including non-small cell lung carcinoma, head and neck carcinoma, triple negative breast carcinoma, melanoma, renal cell carcinoma, urothelial carcinoma, gastric and gastroesophageal carcinoma, colorectal carcinoma, hepatocellular carcinoma, and endometrial carcinoma. The review aims to provide pathologists with a practical guide to the implementation and interpretation of PD-L1 testing by immunohistochemistry.

The Oncocytic Variant of Poorly Differentiated Thyroid Carcinoma Shows a Specific Immune-Related Gene Expression Profile

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) is a rare, follicular cell-derived neoplasm with an unfavorable prognosis. The oncocytic variant of PDTC may be associated with even more adverse outcome than classical PDTC cases, but its specific molecular features are largely unknown. Our aim was to explore the immune-related gene expression profile of oncocytic and classical PDTC, in correlation with clinical and pathological characteristics (including programmed death ligand 1 [PD-L1] expression) and outcome, and in comparison with a control group of well-differentiated follicular carcinomas (WDFCs), including conventional follicular carcinomas (FTCs) and Hürthle cell carcinomas (HCCs).

METHODS

A retrospective series of 48 PDTCs and 24 WDFCs was analyzed by means of NanoString technology employing the nCounter PanCancer Immune Profiling panel. Gene expression data were validated using quantitative real-time polymerase chain reaction.

RESULTS

Oncocytic PDTCs showed a specific immune-related gene expression profile, with higher expression of LAIR2, CD274, DEFB1, IRAK1, CAMP, LCN2, LY96, and APOE, and lower expression of NOD1, as compared to conventional PDTCs. This molecular signature was associated with increased intratumoral lymphocytic infiltration, PD-L1 expression, and adverse outcome. Three of these genes, CD274, DEFB1, and IRAK1, as well as PD-L1 expression, were also the hallmarks of HCCs as compared to FTCs. By contrast, the panel of genes differentially regulated in PDTCs as compared to WDFCs was unrelated to the oncocytic phenotype.

CONCLUSIONS

Our results revealed a distinctive immune-related gene expression profile of oncocytic PDTC and confirmed a more aggressive outcome in this cancer subtype. These findings may provide guidance when exploring novel immunotherapeutic options for oncocytic PDTC patients.

Recent advances in the management of anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is undoubtedly the thyroid cancer histotype with the poorest prognosis. The conventional treatment includes surgery, radiotherapy, and conventional chemotherapy. Surgery should be as complete as possible, securing the airway and ensuring access for nutritional support; the current standard of care of radiotherapy is the intensity-modulated radiation therapy; chemotherapy includes the use of doxorubicin or taxanes (paclitaxel or docetaxel) generally with platin (cisplatin or carboplatin). However, frequently, these treatments are not sufficient and a systemic treatment with kinase inhibitors is necessary. These include multitarget tyrosine kinase inhibitors (Lenvatinib, Sorafenib, Sunitinib, Vandetanib, Axitinib, Pazopanib, Pyrazolo-pyrimidine compounds), single target tyrosine kinase inhibitors (Dabrafenib plus Trametinib and Vemurafenib against BRAF, Gefitinib against EGFR, PPARγ ligands (e.g. Efatutazone), Everolimus against mTOR, vascular disruptors (e.g. Fosbretabulin), and immunotherapy (e.g. Spartalizumab and Pembrolizumab, which are anti PD-1/PD-L1 molecules). Therapy should be tailored to the patients and to the tumor genetic profile. A BRAF mutation analysis is mandatory, but a wider evaluation of tumor mutational status (e.g. by next-generation sequencing) is desirable. When a BRAF^V600E mutation is detected, treatment with Dabrafenib and Trametinib should be preferred: this combination has been approved by the Food and Drug Administration for the treatment of patients with locally advanced or metastatic ATC with BRAF^V600E mutation and with no satisfactory locoregional treatment options. Alternatively, Lenvatinib, regardless of mutational status, reported good results and was approved in Japan for treating unresectable tumors. Other single target mutation agents with fair results are Everolimus when a mutation involving the PI3K/mTOR pathway is detected, Imatinib in case of PDGF-receptors overexpression, and Spartalizumab in case of PD-L1 positive tumors. Several trials are currently evaluating the possible beneficial role of a combinatorial therapy in ATC. Since in this tumor several genetic alterations are usually found, the aim is to inhibit or disrupt several pathways: these combination strategies use therapy targeting angiogenesis, survival, proliferation, and may act against both MAPK and PI3K pathways. Investigating new treatment options is eagerly awaited since, to date, even the molecules with the best radiological results have not been able to provide a durable disease control.

Current and Future Role of Tyrosine Kinases Inhibition in Thyroid Cancer: From Biology to Therapy

Thyroid cancer represents a heterogenous disease whose incidence has increased in the last decades. Although three main different subtypes have been described, molecular characterization is progressively being included in the diagnostic and therapeutic algorithm of these patients. In fact, thyroid cancer is a landmark in the oncological approach to solid tumors as it harbors key genetic alterations driving tumor progression that have been demonstrated to be potential actionable targets. Within this promising and rapid changing scenario, current efforts are directed to improve tumor characterization for an accurate guidance in the therapeutic management. In this sense, it is strongly recommended to perform tissue genotyping to patients that are going to be considered for systemic therapy in order to select the adequate treatment, according to recent clinical trials data. Overall, the aim of this article is to provide a comprehensive review on the molecular biology of thyroid cancer focusing on the key role of tyrosine kinases. Additionally, from a clinical point of view, we provide a thorough perspective, current and future, in the treatment landscape of this tumor.

HDAC Inhibition Induces PD-L1 Expression in a Novel Anaplastic Thyroid Cancer Cell Line

While papillary thyroid cancer (PTC) has largely favorable prognosis, anaplastic thyroid cancer (ATC) is a rare but extremely aggressive malignancy with grim clinical outcome. Even though new therapeutic options are emerging for ATC, additional preclinical models and novel combinations are needed for specific subsets of patients. We established a novel cell line (PF49) from the malignant pleural effusion of a 68-year-old male patient with ATC that rapidly transformed from a BRAF and TERT promoter mutant PTC. PF49 cells demonstrated a robust migratory activity in vitro and strong invasive capacity in vivo in a pleural carcinosis model. Combined BRAF and MEK inhibition decreased the proliferation and migration of PF49 cells, however could not induce cell death. Importantly, HDAC inhibitor treatment with SAHA or valproic acid induced cell cycle arrest and strongly increased PD-L1 expression of the tumor cells. Induction of PD-L1 expression was also present when paclitaxel-cisplatin chemotherapeutic treatment was combined with HDAC inhibitor treatment. Increased PD-L1 expression after HDAC inhibition was recapitulated in an international ATC cell model. Our data suggest that HDAC inhibition alone or in combination with standard chemotherapy may potentiate anaplastic thyroid cancer cells for immunotherapy.

Recent Improvements in Genomic and Transcriptomic Understanding of Anaplastic and Poorly Differentiated Thyroid Cancers

Anaplastic thyroid cancer (ATC) is a lethal human cancer with a 5-year survival rate of less than 10%. Recently, its genomic and transcriptomic characteristics have been extensively elucidated over 5 years owing to advance in high throughput sequencing. These efforts have extended molecular understandings into the progression mechanisms and therapeutic vulnerabilities of aggressive thyroid cancers. In this review, we provide an overview of genomic and transcriptomic alterations in ATC and poorly-differentiated thyroid cancer, which are distinguished from differentiated thyroid cancers. Clinically relevant genomic alterations and deregulated signaling pathways will be able to shed light on more effective prevention and stratified therapeutic interventions for affected patients.

New Therapies for Advanced Thyroid Cancer

Thyroid cancer is the most common endocrine cancer. The discovery of new biomarkers for thyroid cancer has significantly improved the understanding of the molecular pathogenesis of thyroid cancer, thus allowing more personalized treatments for patients with thyroid cancer. Most of the recently discovered targeted therapies inhibit the known oncogenic mechanisms in thyroid cancer initiation and progression such as MAPK pathway, PI3K/Akt-mTOR pathways, or VEGF. Despite the significant advances in molecular testing and the discoveries of new and promising therapeutics, effective treatments for advanced and metastatic, iodine-refractory thyroid cancer are still lacking. Here, we aim to summarize the current understanding of the genetic alterations and the dysregulated pathways in thyroid cancer and to discuss the most recent targeted therapies and immunotherapy for advanced thyroid cancer with a promising anti-tumor activity and clinical benefit.

Telomerase and Telomeres Biology in Thyroid Cancer

Telomere and telomerase regulation contributes to the onset and evolution of several tumors, including highly aggressive thyroid cancers (TCs). TCs are the most common endocrine malignancies and are generally characterized by a high rate of curability. However, a small but significant percentage develops distant metastasis or progresses into undifferentiated forms associated with bad prognosis and for which poor therapeutic options are available. Mutations in telomerase reverse transcriptase (TERT) promoter are among the most credited prognostic marker of aggressiveness in TCs. Indeed, their frequency progressively increases passing from indolent lesions to aggressive and anaplastic forms. TERT promoter mutations create binding sites for transcription factors, increasing TERT expression and telomerase activity. Furthermore, aggressiveness of TCs is associated with TERT locus amplification. These data encourage investigating telomerase regulating pathways as relevant drivers of TC development and progression to foster the identification of new therapeutics targets. Here, we summarize the current knowledge about telomere regulation and TCs, exploring both canonical and less conventional pathways. We discuss the possible role of telomere homeostasis in mediating response to cancer therapies and the possibility of using epigenetic drugs to re-evaluate the use of telomerase inhibitors. Combined treatments could be of support to currently used therapies still presenting weaknesses.

PD-1 Ligand Expression in Epithelial Thyroid Cancers: Potential Clinical Implications

The new immunotherapy targeting the programmed cell death 1 (PD-1) receptor and its cognate ligand PD-L1 has renewed hopes of eradicating the most difficult human cancers to treat. Among these, there are the poorly differentiated and anaplastic thyroid cancers, unresponsive to all the therapies currently in use. In the present review we will summarize information regarding the expression of PD-L1 in the different thyroid cancer histotypes, its correlation with clinicopathological features, and its potential prognostic value. Then, we will evaluate the available data indicating the PD-1/PD-L1 axis as a promising target for thyroid cancer therapy.