Targeting Non-Oncogene Addiction: Focus on Thyroid Cancer

Specific photodamage on HT-29 cancer cells leads to endolysosomal failure and autophagy blockage by cathepsin depletion

Endolysosomes perform a wide range of cellular functions, including nutrient sensing, macromolecule digestion and recycling, as well as plasma membrane repair. Because of their high activity in cancerous cells, endolysosomes are attractive targets for the development of novel cancer treatments. Light-activated compounds termed photosensitizers (PS) can catalyze the oxidation of specific biomolecules and intracellular organelles. To selectively damage endosomes and lysosomes, HT-29 colorectal cancer cells were incubated with nanomolar concentrations of meso-tetraphenylporphine disulfonate (TPPS2a), an amphiphilic PS taken up via endocytosis and activated by green light (522 nm, 2.1 J.cm-1). Several cellular responses were characterized by a combination of immunofluorescence and immunoblotting assays. We showed that TPPS2a photosensitization blocked autophagic flux without extensive endolysosomal membrane rupture. Nevertheless, there was a severe functional failure of endolysosomes due to a decrease in CTSD (cathepsin D, 55%) and CTSB (cathepsin B, 52%) maturation. PSAP (prosaposin) processing (into saposins) was also considerably impaired, a fact that could be detrimental to glycosphingolipid homeostasis. Therefore, photosensitization of HT-29 cells previously incubated with a low concentration of TPPS2a promotes endolysosomal dysfunction, an effect that can be used to improve cancer therapies.

Targeting cyclin D1 as a therapeutic approach for papillary thyroid carcinoma

Cyclin D1 functions as a mitogenic sensor that specifically binds to CDK4/6, thereby integrating external mitogenic inputs and cell cycle progression. Cyclin D1 interacts with transcription factors and regulates various important cellular processes, including differentiation, proliferation, apoptosis, and DNA repair. Therefore, its dysregulation contributes to carcinogenesis. Cyclin D1 is highly expressed in papillary thyroid carcinoma (PTC). However, the particular cellular mechanisms through which abnormal cyclin D1 expression causes PTC are poorly understood. Unveiling the regulatory mechanisms of cyclin D1 and its function in PTC may help determine clinically effective strategies, and open up better opportunities for further research, leading to the development of novel PTC regimens that are clinically effective. This review explores the mechanisms underlying cyclin D1 overexpression in PTC. Furthermore, we discuss the role of cyclin D1 in PTC tumorigenesis via its interactions with other regulatory elements. Finally, recent progress in the development of therapeutic options targeting cyclin D1 in PTC is examined and summarized.

The Autoantibodies against Tumor-Associated Antigens as Potential Blood-Based Biomarkers in Thyroid Neoplasia: Rationales, Opportunities and Challenges

The Autoantibodies targeting Tumor-Associated Antigens (TAA-AAbs) emerge as a result of a variety of tumor-related immunogenic stimuli and may be regarded as the eyewitnesses to the anti-tumor immune response. TAA-AAbs may be readily detected in peripheral blood to unveil the presence of a particular TAA-expressing tumor, and a fair number of TAAs eliciting the tumor-associated autoantibody response have been identified. The potential of TAA-AAbs as tumor biomarkers has been extensively studied in many human malignancies with a major influence on public health; however, tumors of the endocrine system, and, in particular, the well-differentiated follicular cell-derived thyroid neoplasms, remain understudied in this context. This review provides a detailed perspective on and legitimate rationales for the potential use of TAA-AAbs in thyroid neoplasia, with particular reference to the already established diagnostic implications of the TAA-AAbs in human cancer, to the windows for improvement and diagnostic niches in the current workup strategies in nodular thyroid disease and differentiated thyroid cancer that TAA-AAbs may successfully occupy, as well as to the proof-of-concept studies demonstrating the usefulness of TAA-AAbs in thyroid oncology, particularly for the pre-surgical discrimination between tumors of different malignant potential in the context of the indeterminate results of the fine-needle aspiration cytology.

CASC2 inhibits the growth, migration, and invasion of thyroid cancer cells through sponging miR-18a-5p/FIH1 axis

Long noncoding RNA (lncRNA) Cancer Susceptibility 2 (CASC2) has been proved to contribute to the development of cancers. However, the mechanism behind the action of CASC2 in thyroid cancer is not quite clear. We demonstrated that CASC2 was downregulated in thyroid cancer. We noted that CASC2 overexpression restrained the growth, migration, and invasion of thyroid cancer cells, whereas CASC2 depletion caused opposite trends. Bioinformatics analysis predicted that hypoxia inducible factor 1 subunit alpha inhibitor (FIH-1) was potentially targeted by miR-18a-5p, which was confirmed by luciferase reporter assay. Upregulation of FIH-1 abrogated the promotive effect of miR-18a-5p on the growth and invasion of thyroid cancer cells. In addition, CASC2 serves as a competing endogenous RNA (ceRNA) and a ''sponge'' for miR-18a-5p, thereby regulating the expression of FIH-1. These data elucidated the CASC2/miR-18a-5p ceRNA network in thyroid cancer pathogenesis.

Enhanced expression of Cyclin D1 and C-myc, a prognostic factor and possible mechanism for recurrence of papillary thyroid carcinoma

A direct association has been shown between Cyclin D1 and C-myc gene expressions and the proliferation of human thyroid tumor cells. Our previous study showed that increased β catenin led to a reduction in disease-free probability in patients with papillary thyroid cancer. This study was designed to investigate Cyclin D1 and C-myc genes as targets for β catenin function in PTC and to determine the association between genes expression and staging, recurrence, metastasis, and disease-free survival of PTC. This study was conducted via a thorough investigation of available data from medical records as well as paraffin blocks of 77 out of 400 patients over a 10-year period. Cyclin D1 and C-myc gene expression levels were measured using real-time polymerase chain reaction (RT-PCR) and the Kaplan-Meier method was used to evaluate disease-free survival. Higher levels of Cyclin D1 and C-myc gene expressions were observed in patients with recurrence by 8.5 (P = 0.004) and 19.5 (p = 0.0001) folds, respectively. A significant positive correlation was found between Cyclin D1 expression and the cumulative dose of radioactive iodine received by patients (r = −0.2, p value = 0.03). The ten-year survival rate in the patients included in this study was 98.25% while disease-free survival was 48.1%. Higher Cyclin D1 and C-myc gene expression levels were observed in patients with recurrence/distant metastasis. Inversely, lower expression of Cyclin D1 and C-myc genes were associated with better survival of patients (SD, 0.142-0.052) (Mantel-Cox test, P = 0.002). The enhancement of Cyclin D1 and C-myc gene expression may be a potential mechanism for recurrence and aggressiveness of PTC.

Targeting Cancer Lysosomes with Good Old Cationic Amphiphilic Drugs

Being originally discovered as cellular recycling bins, lysosomes are today recognized as versatile signaling organelles that control a wide range of cellular functions that are essential not only for the well-being of normal cells but also for malignant transformation and cancer progression. In addition to their core functions in waste disposal and recycling of macromolecules and energy, lysosomes serve as an indispensable support system for malignant phenotype by promoting cell growth, cytoprotective autophagy, drug resistance, pH homeostasis, invasion, metastasis, and genomic integrity. On the other hand, malignant transformation reduces the stability of lysosomal membranes rendering cancer cells sensitive to lysosome-dependent cell death. Notably, many clinically approved cationic amphiphilic drugs widely used for the treatment of other diseases accumulate in lysosomes, interfere with their cancer-promoting and cancer-supporting functions and destabilize their membranes thereby opening intriguing possibilities for cancer therapy. Here, we review the emerging evidence that supports the supplementation of current cancer therapies with lysosome-targeting cationic amphiphilic drugs.