Anaplastic thyroid carcinoma (ATC) and squamous thyroid carcinoma (STC) are both rare and advanced thyroid malignancies with a very poor prognosis and an average median survival time of 5 months and less than 20% of affected patients are alive 1 year after diagnosis. The clinical management of both ATC and STC is very similar because they are not particularly responsive to radiotherapy and chemotherapy. This inspired us to explore a novel and effective clinically approved therapy for ATC treatment. Histone deacetylase inhibitor (HDACi) drugs are recently FDA-approved drug for malignancies, especially for blood cell cancers. Therefore, we investigated whether an HDACi drug acts as an effective anticancer drug for advanced thyroid cancers. Cell viability analysis of panobinostat treatment demonstrated a significant IC50 of 0.075 µM on SW579 STC cells. In addition, panobinostat exposure activated histone acetylation and triggered cell death mainly through cell cycle arrest and apoptosis-related protein activation. Using CRISPR/Cas9 to knock out HDAC1 and HDAC2 genes in SW579 cells, we observed that the histone acetylation level and cell cycle arrest were enhanced without any impact on cell growth. Furthermore, HDAC1 and HDAC2 double knockout (KO) cells showed dramatic cell apoptosis activation compared to HDAC1 and HDAC2 individual KO cells. This suggests expressional and biofunctional compensation between HDAC1 and HDAC2 on SW579 cells. This study provides strong evidence that panobinostat can potentially be used in the clinic of advanced thyroid cancer patients.

The 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1) is a potential regulatory node in the mevalonate pathway that is frequently dysregulated in tumors. This study found that HMGCS1 expression is upregulated in stomach adenocarcinoma samples of patients and tumorspheres of gastric cancer cells. HMGCS1 elevates the expression levels of the pluripotency genes Oct4 and SOX-2 and contributes to tumorsphere formation ability in gastric cancer cells. HMGCS1 also promotes in vitro cell growth and progression and the in vivo tumor growth and lung metastasis of gastric cancer cells. After blocking the mevalonate pathway by statin and dipyridamole, HMGCS1 exerts nonmetabolic functions in enhancing gastric cancer progression. Furthermore, the level and nuclear translocation of HMGCS1 in gastric cancer cells are induced by serum deprivation. HMGCS1 binds to and activates Oct4 and SOX-2 promoters. HMGCS1 also enhances the integrated stress response (ISR) and interacts with the endoplasmic reticulum (ER) stress transducer protein kinase RNA-like endoplasmic reticulum kinase (PERK). Our results reveal that HMGCS1 contributes to gastric cancer progression in both metabolic and nonmetabolic manners.

Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast cancer. TNBC does not express the estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2. Cytotoxic chemotherapy and surgery are the current therapeutic strategies for TNBC patients, but the chemoresistance of TNBC limits the efficiency of this strategy and shortens the lifespan of patients. The exploration of targeted therapy is ongoing in TNBC research. The aim of the present study was to identify the mechanism underlying acquired resistance in TNBC through the exploration of the relationship between the expression of USP7 and of ABCB1. We found that ubiquitin specific protease 7 (USP7) is a potential therapeutic target for overcoming the chemoresistance of TNBC. USP7 overexpression increased the chemoresistance of TNBC, while the knockdown of USP7 effectively increased the chemosensitivity of chemoresistant TNBC. A USP7 inhibitor effectively induced apoptosis and suppressed metastasis in chemoresistant TNBC. We further clarified that USP7 is a specific deubiquitinating enzyme for ABCB1 that plays an essential role in drug resistance. USP7 directly interacted with ABCB1 and regulated its stability. We concluded that USP7 promotes the chemoresistance of TNBC by stabilizing the ABCB1 protein.

Invasion is the most prominent lethal feature of malignant cancer. However, how cell proliferation, another important feature of tumor development, is integrated with tumor invasion and the subsequent cell dissemination from primary tumors is not well understood. Proliferating cell nuclear antigen (PCNA) is essential for DNA replication in cancer cells. Loss of phosphorylation at tyrosine 211 (Y211) in PCNA (pY211-PCNA) mitigates PCNA function in proliferation, triggers replication fork arrest/collapse, which in turn sets off an anti-tumor inflammatory response, and suppresses distant metastasis. Here, we show that pY211-PCNA is important in stromal activation in tumor tissues. Loss of the phosphorylation resulted in reduced expression of mesenchymal proteins as well as tumor progenitor markers, and of the ability of invasion. Spontaneous mammary tumors that developed in mice lacking Y211 phosphorylation contained fewer tumor-initiating cells compared to tumors in wild-type mice. Our study demonstrates a novel function of PCNA as an essential factor for maintaining cancer stemness through Y211 phosphorylation.

Breast cancer is the most common malignancy in women and the second leading cause of cancer death in women. Triple negative breast cancer (TNBC) subtype is a breast cancer subset without ER (estrogen receptor), PR (progesterone receptor) and HER2 (human epidermal growth factor receptor 2) expression, limiting treatment options and presenting a poorer survival rate. Thus, we investigated whether histone deacetylation inhibitor (HDACi) could be used as potential anti-cancer therapy on breast cancer cells. In this study, we found TNBC and HER2-enriched breast cancers are extremely sensitive to Panobinostat, Belinostat of HDACi via experiments of cell viability assay, apoptotic marker identification and flow cytometry measurement. On the other hand, we developed a bioluminescence-based live cell non-invasive apoptosis detection sensor (NIADS) detection system to evaluate the quantitative and kinetic analyses of apoptotic cell death by HDAC treatment on breast cancer cells. In addition, the use of HDACi may also contribute a synergic anti-cancer effect with co-treatment of chemotherapeutic agent such as doxorubicin on TNBC cells (MDA-MB-231), but not in breast normal epithelia cells (MCF-10A), providing therapeutic benefits against breast tumor in the clinic.