Astragaloside IV enhances the sensitivity of breast cancer stem cells to paclitaxel by inhibiting stemness

Background: Chemotherapy is one of the common treatments for breast cancer. The induction of cancer stem cells (CSCs) is an important reason for chemotherapy failure and breast cancer recurrence. Astragaloside IV (ASIV) is one of the effective components of the traditional Chinese medicine (TCM) Astragalus membranaceus, which can improve the sensitivity of various tumors to chemotherapy drugs. Here, we explored the sensitization effect of ASIV to chemotherapy drug paclitaxel (PTX) in breast cancer from the perspective of CSCs. Methods: The study included both in vitro and in vivo experiments. CSCs from the breast cancer cell line MCF7 with stem cell characteristics were successfully induced in vitro. Cell viability and proliferation were detected using the Cell Counting Kit-8 (CCK-8) and colony formation assays, and flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) methods were performed to detect cell apoptosis. Stemness-related protein expression was determined by western blotting (WB) and immunohistochemistry (IHC). Body weight, histopathology, and visceral organ damage of mice were used to monitor drug toxicity. Results: The expression of stemness markers including Sox2, Nanog, and ALDHA1 was stronger in MCF7-CSCs than in MCF7. PTX treatment inhibited the proliferation of tumor cells by promoting cell apoptosis, whereas the stemness of breast cancer stem cells (BCSCs) resisted the effects of PTX. ASIV decreased the stemness of BCSCs, increased the sensitivity of BCSCs to PTX, and synergistically promoted PTX-induced apoptosis of breast cancer cells. Our results showed that the total cell apoptosis rate increased by about 25% after adding ASIV compared with BCSCs treated with PTX alone. The in vivo experiments demonstrated that ASIV enhanced the ability of PTX to inhibit the growth of breast cancer. WB and IHC showed that ASIV reduced the stemness of CSCs. Conclusions: In this study, the resistance of breast cancer to PTX was attributed to the existence of CSCs; ASIV weakened the resistance of MCF7-CSCs to PTX by significantly attenuating the hallmarks of breast cancer stemness and improved the efficacy of PTX. Keywords: Breast cancer; cancer stem cells (CSCs); astragaloside IV (ASIV); paclitaxel (PTX); chemotherap

The protective role of DOT1L in UV-induced melanomagenesis

The DOT1L histone H3 lysine 79 (H3K79) methyltransferase plays an oncogenic role in MLL-rearranged leukemogenesis. Here, we demonstrate that, in contrast to MLL-rearranged leukemia, DOT1L plays a protective role in ultraviolet radiation (UVR)-induced melanoma development. Specifically, the DOT1L gene is located in a frequently deleted region and undergoes somatic mutation in human melanoma. Specific mutations functionally compromise DOT1L methyltransferase enzyme activity leading to reduced H3K79 methylation. Importantly, in the absence of DOT1L, UVR-induced DNA damage is inefficiently repaired, so that DOT1L loss promotes melanoma development in mice after exposure to UVR. Mechanistically, DOT1L facilitates DNA damage repair, with DOT1L-methylated H3K79 involvement in binding and recruiting XPC to the DNA damage site for nucleotide excision repair (NER). This study indicates that DOT1L plays a protective role in UVR-induced melanomagenesis

Mi-2β promotes immune evasion in melanoma by activating EZH2 methylation

Recent development of new immune checkpoint inhibitors has been particularly successfully in cancer treatment, but still the majority patients fail to benefit. Converting resistant tumors to immunotherapy sensitive will provide a significant improvement in patient outcome. Here we identify Mi-2β as a key melanoma-intrinsic effector regulating the adaptive anti-tumor immune response. Studies in genetically engineered mouse melanoma models indicate that loss of Mi-2β rescues the immune response to immunotherapy in vivo. Mechanistically, ATAC-seq analysis shows that Mi-2β controls the accessibility of IFN-γ-stimulated genes (ISGs). Mi-2β binds to EZH2 and promotes K510 methylation of EZH2, subsequently activating the trimethylation of H3K27 to inhibit the transcription of ISGs. Finally, we develop an Mi-2β-targeted inhibitor, Z36-MP5, which reduces Mi-2β ATPase activity and reactivates ISG transcription. Consequently, Z36-MP5 induces a response to immune checkpoint inhibitors in otherwise resistant melanoma models. Our work provides a potential therapeutic strategy to convert immunotherapy resistant melanomas to sensitive ones

Pharmacological targeting of STK19 inhibits oncogenic NRAS driven melanomagenesis

黑色素瘤是由黑色素细胞恶性转化产生的恶性程度极高的皮肤癌，含有NRAS激活突变的黑色素瘤约占20-30%，但至今还未有靶向NRAS的有效黑色素瘤治疗方案。针对这一难题，波士顿大学医学中心崔儒涛教授、厦门大学生命科学学院邓贤明教授、复旦大学附属肿瘤医院王鹏教授组成的联合研究团队利用激酶组siRNA文库筛选发现新颖的丝/苏氨酸激酶STK19是NRAS的上游激活子，进一步分子机制研究揭示STK19通过磷酸化NRAS的89位丝氨酸（S89）促进了NRAS介导的黑色素细胞恶性转化。该研究揭示了一种经由新颖激酶STK19调控NRAS突变黑色素瘤的分子机制，验证了STK19有望作为NRAS介导的黑色素瘤的有效靶标，为发展新的黑色素瘤靶向药物提供了先导化合物，同时也为发展其它素有“癌基因之王---RAS”驱动的相关肿瘤靶向药物发展提供了新思路。该论文由波士顿大学医学中心、厦门大学生命科学学院、复旦大学附属肿瘤医院等单位合作完成，共同第一作者厦门大学生命科学学院博士生张婷负责了该系列化合物的设计、合成与优化，崔儒涛教授、邓贤明教授和王鹏教授为共同通讯作者。【Abstract】Activating mutations in NRAS account for 20-30% of melanoma, but despite decades of research and in contrast to BRAF, no effective anti-NRAS therapies have been forthcoming. Here we identify a previously uncharacterized serine/threonine kinase STK19 as a novel NRAS activator. STK19 phosphorylates NRAS to enhance its binding to its downstream effectors and promotes oncogenic NRAS-mediated melanocyte malignant transformation. A recurrent D89N substitution in STK19 whose alterations were identified in 25% of human melanomas represents a gain-of-function mutation that interacts better with NRAS to enhance melanocyte transformation. STK19 D89N knockin leads to skin hyperpigmentation and promotes NRAS Q61R -driven melanomagenesis in vivo. Finally, we developed ZT-12-037-01 (1a) as a specific STK19-targeted inhibitor and showed that it effectively blocks oncogenic NRAS-driven melanocyte malignant transformation and melanoma growth in vitro and in vivo. Together, our findings provide a new and viable therapeutic strategy for melanomas harboring NRAS mutations.We thank Drs. Norman Sharpless and David Fisher for kindly providing the loxP/STOP/loxP NRAS Q61R knockin (LSL-NRAS Q61R ) mice. We thank Dr. Anurag Singh for kindly sharing cell lines. We also thank Drs. X. Shirley Liu, Tao Wang, Wantao Chen, Dali Liu, Chunxiao Xu, Jianming Zhang and Junrong Zou for discussion and assistance. This work was supported by grants from Boston University (to R.C.), the National Key R&D Program and the National Natural Science Foundation of China (No. 2017YFA0504504, 2016YFA0502001, 81422045, U1405223 and 81661138005 to X.D.), the Fundamental Research Funds for the Central Universities of China (No. 20720160064 to X.D.), and the Program of Introducing Talents of Discipline to Universities (111 Project, B12001).该研究得到了科技部重点研发计划、国家自然科学基金委和中央高校基本科研业务费等的资助

Astragaloside IV enhances the sensitivity of breast cancer stem cells to paclitaxel by inhibiting stemness.

Chemotherapy is one of the common treatments for breast cancer. The induction of cancer stem cells (CSCs) is an important reason for chemotherapy failure and breast cancer recurrence. Astragaloside IV (ASIV) is one of the effective components of the traditional Chinese medicine (TCM) , which can improve the sensitivity of various tumors to chemotherapy drugs. Here, we explored the sensitization effect of ASIV to chemotherapy drug paclitaxel (PTX) in breast cancer from the perspective of CSCs. The study included both and experiments. CSCs from the breast cancer cell line MCF7 with stem cell characteristics were successfully induced . Cell viability and proliferation were detected using the Cell Counting Kit-8 (CCK-8) and colony formation assays, and flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) methods were performed to detect cell apoptosis. Stemness-related protein expression was determined by western blotting (WB) and immunohistochemistry (IHC). Body weight, histopathology, and visceral organ damage of mice were used to monitor drug toxicity. The expression of stemness markers including Sox2, Nanog, and ALDHA1 was stronger in MCF7-CSCs than in MCF7. PTX treatment inhibited the proliferation of tumor cells by promoting cell apoptosis, whereas the stemness of breast cancer stem cells (BCSCs) resisted the effects of PTX. ASIV decreased the stemness of BCSCs, increased the sensitivity of BCSCs to PTX, and synergistically promoted PTX-induced apoptosis of breast cancer cells. Our results showed that the total cell apoptosis rate increased by about 25% after adding ASIV compared with BCSCs treated with PTX alone. The experiments demonstrated that ASIV enhanced the ability of PTX to inhibit the growth of breast cancer. WB and IHC showed that ASIV reduced the stemness of CSCs. In this study, the resistance of breast cancer to PTX was attributed to the existence of CSCs; ASIV weakened the resistance of MCF7-CSCs to PTX by significantly attenuating the hallmarks of breast cancer stemness and improved the efficacy of PTX. [Abstract copyright: 2023 Translational Cancer Research. All rights reserved.

The protective role of DOT1L in UV-induced melanomagenesis

The DOT1L histone H3 lysine 79 (H3K79) methyltransferase plays an oncogenic role in MLL-rearranged leukemogenesis. Here, we demonstrate that, in contrast to MLL-rearranged leukemia, DOT1L plays a protective role in ultraviolet radiation (UVR)-induced melanoma development. Specifically, the DOT1L gene is located in a frequently deleted region and undergoes somatic mutation in human melanoma. Specific mutations functionally compromise DOT1L methyltransferase enzyme activity leading to reduced H3K79 methylation. Importantly, in the absence of DOT1L, UVR-induced DNA damage is inefficiently repaired, so that DOT1L loss promotes melanoma development in mice after exposure to UVR. Mechanistically, DOT1L facilitates DNA damage repair, with DOT1L-methylated H3K79 involvement in binding and recruiting XPC to the DNA damage site for nucleotide excision repair (NER). This study indicates that DOT1L plays a protective role in UVR-induced melanomagenesis

Stem cell heterogeneity, plasticity, and regulation

As a population of homogeneous cells with both self-renewal and differentiation potential, stem cell pools are highly compartmentalized and contain distinct subsets that exhibit stable but limited heterogeneity during homeostasis. However, their striking plasticity is showcased under natural or artificial stress, such as injury, transplantation, cancer, and aging, leading to changes in their phenotype, constitution, metabolism, and function. The complex and diverse network of cell-extrinsic niches and signaling pathways, together with cell-intrinsic genetic and epigenetic regulators, tightly regulate both the heterogeneity during homeostasis and the plasticity under perturbation. Manipulating these factors offers better control of stem cell behavior and a potential revolution in the current state of regenerative medicine. However, disruptions of normal regulation by genetic mutation or excessive plasticity acquisition may contribute to the formation of tumors. By harnessing innovative techniques that enhance our understanding of stem cell heterogeneity and employing novel approaches to maximize the utilization of stem cell plasticity, stem cell therapy holds immense promise for revolutionizing the future of medicine

Melanogenesis and the Targeted Therapy of Melanoma

Pigment production is a unique character of melanocytes. Numerous factors are linked with melanin production, including genetics, ultraviolet radiation (UVR) and inflammation. Understanding the mechanism of melanogenesis is crucial to identify new preventive and therapeutic strategies in the treatment of melanoma. Here, we reviewed the current available literatures on the mechanisms of melanogenesis, including the signaling pathways of UVR-induced pigment production, MC1R’s central determinant roles and MITF as a master transcriptional regulator in melanogenesis. Moreover, we further highlighted the role of targeting BRAF, NRAS and MC1R in melanoma prevention and treatment. The combination therapeutics of immunotherapy and targeted kinase inhibitors are becoming the newest therapeutic option in advanced melanoma