Cancer Stem Cells and their Management in Cancer Therapy

An overview of the past decade of bufalin in the treatment of refractory and drug-resistant cancers: current status, challenges, and future perspectives

Profound progress has been made in cancer treatment in the past three decades. However, drug resistance remains prevalent and a critical challenge. Drug resistance can be attributed to oncogenes mutations, activated defensive mechanisms, ATP-bind cassette transporters overexpression, cancer stem cells, etc. Chinese traditional medicine toad venom has been used for centuries for different diseases, including resistant cancers. Bufalin is one of the bufadienolides in toad venom that has been extensively studied for its potential in refractory and drug-resistant cancer treatments in vitro and in vivo. In this work, we would like to critically review the progress made in the past decade (2013-2022) of bufalin in overcoming drug resistance in cancers. Generally, bufalin shows high potential in killing certain refractory and resistant cancer cells via multiple mechanisms. More importantly, bufalin can work as a chemo-sensitizer that enhances the sensitivity of certain conventional and targeted therapies at low concentrations. In addition, the development of bufalin derivatives was also briefly summarized and discussed. We also analyzed the obstacles and challenges and provided possible solutions for future perspectives. We hope that the collective information may help evoke more effort for more in-depth studies and evaluation of bufalin in both lab and possible clinical trials.

Targeting the 'garbage-bin' to fight cancer: HDAC6 inhibitor WT161 has an anti-tumor effect on osteosarcoma and synergistically interacts with 5-FU

An imbalance between protein aggregation and protein degradation may induce 'stress' in the functionality of the endoplasmic reticulum (ER). There are quality control (QC) mechanisms to minimize misfolding and to eliminate misfolded proteins before aggregation becomes lethal for the cell. Proper protein folding and maturation is one of the crucial functions of the ER. Chaperones of the ER and folding enzymes guarantee correct conformational maturation of emerging secretory proteins. Histone deacetylase (HDAC) 6 (HDAC6) is a masterpiece coordinating the cell response to protein aggregate formation. The balance between HDAC6 and its partner Valosin-containing protein/p97 determines the fate of polyubiquitinated misfolded proteins. WT161 is a terrific, selective, and bioavailable HDAC6 inhibitor. WT161 selectively inhibits HDAC6 and adequately increases levels of acetylated α-tubulin. This compound induces accumulation of acetylated tubulin and cytotoxicity in multiple myeloma (MM) cells. In this journal, Sun et al. (Biosci. Rep.41, DOI: 10.1042/BSR20203905) identified that WT161 suppresses the cell growth of osteosarcoma cells. This discovery opens the door to future chemotherapeutic regimens of this bone neoplasm.

Suppression of CD13 Enhances the Cytotoxic Effect of Chemotherapeutic Drugs in Hepatocellular Carcinoma Cells

Multidrug resistance (MDR) of hepatocellular carcinoma (HCC) is a serious problem that directly hinders the effect of chemotherapeutics. In this study, we mainly explore the molecular mechanism of ROS-induced CD13 expression using hepatocarcinoma cells as the research object. We show that the drug of fluorouracil (5FU), epirubicin (EPI) and gemcitabine (GEM) can induce ROS generation, activate Ets2 and promote CD13 expression. Meanwhile, CD13 can activate NRF1 and up-regulate ROS scavenging genes transcription, such as SOD1, GPX1, GPX2 and GPX3, leading to down-regulation of intracellular ROS level and reducing the sensitivity of cells to chemotherapy agent. We also detected the anti-tumor effect of the combination therapy, CD13 inhibitor ubenimex and a variety of conventional anti-cancer drugs, such as 5FU, EPI, GEM, pemetrexed (Pem) and paclitaxel (PTX) were employed in combination. Ubenimex enhances the sensitivity of different chemotherapeutic agents and cooperates with chemotherapeutic agents to suppress tumor growth in vitro and in vivo. In general, overexpression of CD13 can lead to chemotherapy resistance, and CD13 inhibitor can reverse this effect. Combination of chemotherapy agent and ubenimex will become a potential treatment strategy for liver cancer resistance.