Synthesis and Biological Evaluation of Steviol Derivatives with Improved Cytotoxic Activity and Selectivity.

Steviol is an ent-kaurene diterpenoid with interesting pharmacological activity. Several steviol derivatives with an exo-methylene cyclopentanone unit were discovered as potent antitumor agents. However, their poor selectivity for tumor cells relative to normal cells reduces their prospects as potential anticancer drugs. In this study, based on previous work, 32 steviol derivatives, including 28 new analogues, were synthesized. Their cytotoxicity against tumor cells and normal cells was evaluated. Several new derivatives, such as 7a, 7h, and 8f, with improved cytotoxic selectivity and antiproliferative activity were obtained, and the structure-activity relationship correlations were investigated. The new compound 8f displayed potent antiproliferative activity against Huh7 cells (IC50 = 2.6 µM) and very weak cytotoxicity against the corresponding normal cells HHL5 (IC50 = 97.0 µM). Further investigation showed that 8f arrested the cell cycle at the G0/G1 phase and caused reactive oxygen species overproduction, decreased mitochondrial membrane potential, and induced apoptosis of Huh7 cells through inhibition of the PI3K/Akt/mTOR and NF-κB pathway as well as upregulation of Bax/Bcl-2 ratio. The present study suggested that 8f is a promising lead compound for new cancer therapies, and the results presented herein may encourage the further modification of steviol for additional derivatives with enhanced efficacy and selectivity.

Pseudophosphatase STYX is induced by Helicobacter pylori and promotes gastric cancer progression by inhibiting FBXO31 function.

Gastric cancer (GC) is one of the most common malignancies in the world and ranks third in terms of cancer-related deaths. The catalytically inactive pseudophosphatase STYX (serine/threonine/tyrosine interacting protein) is a member of the protein tyrosine phosphatase family. It has been recently reported that STYX functions as a potential oncogene in different types of cancers. However, the potential role and regulatory mechanism of STYX in GC remains unknown. In this study, we find that STYX is highly expressed in GC tissues compared with adjacent noncancerous tissues and closely correlates with the prognosis of GC patients. STYX overexpression facilitates the proliferation and migration in GC cells, whereas STYX knockdown has the opposite effects. Nude mice experiments indicate that STYX knockdown in GC cells dramatically suppresses the tumor growth and lung metastasis in vivo. Mechanically, our results suggest that STYX interacts with the F-box protein FBXO31 and disrupts the degradation function of FBXO31 to its target proteins CyclinD1 and Snail1, thereby increasing the level of CyclinD1 and Snail1 in GC. STYX-mediated biological changes can be reversed by the co-expression of STYX and FBXO31 in GC cells. In addition, transcription factor c-Jun can enhance the expression of STYX in GC. The expression of STYX can also be induced by Helicobacter pylori (H. pylori) infection in c-Jun-dependent manner. Together, our present study suggests that STYX plays an oncogenic role in GC by inhibiting FBXO31 function and represents a potential therapeutic target and prognostic biomarker in GC.

Mitochondria-Targeted Triphenylphosphonium Conjugated C-3 Modified Betulin: Synthesis, Antitumor Properties and Mechanism of Action.

A series of mitochondria-targeted triphenylphosphonium conjugated C-3 modified betulin were synthesized and evaluated against tumor cells. As a result, a new derivative 13 i, the conjugate of 3-O-(3'-acetylphenylacetate)-betulin with triphenylphosphonium, was identified as the one with the best anti-tumor effect. Conjugate 13 i significantly inhibited HCT116 cells with IC50 at 0.66 µM. While betulin, C-3 modified betulin, and the triphenylphosphonium moiety showed no inhibition of HCT116 cell proliferation at 20 µM. More importantly, 13 i exhibited a more cytotoxic effect against the tumor cell HCT116 than normal cell NCM460. Mode of action studies demonstrated that 13 i induced the G2/M phase cell cycle arrest and apoptosis in HCT116 cells through the mitochondrial pathway. Structure-activity relationship analysis revealed that integration of triphenylphosphonium moiety into the C-28 of betulin can greatly improve cytotoxicity. Appropriate modification on C-3 of the conjugate would improve the selectivity.

Circular RNA hsa_circ_0004872 inhibits gastric cancer progression via the miR-224/Smad4/ADAR1 successive regulatory circuit.

BACKGROUND: Emerging evidence has shown that circular RNAs (circRNAs) play a crucial regulatory role in the occurrence and development of cancer. Exploring the roles and mechanisms of circRNAs in tumorigenesis and progression may help to identify new diagnostic markers and therapeutic targets. In the present study, we investigated the role and regulatory mechanism of hsa_circ_0004872 in gastric cancer (GC). METHODS: qRT-PCR was used to determine the expression of hsa_circ_0004872 in GC tissues and cells. EdU, CCK-8, transwell and scratch wound healing assays were used to assess the role of hsa_circ_0004872 in GC cell proliferation, invasion and migration, respectively. Subcutaneous and tail vein tumor injections in nude mice were used to assess the role of hsa_circ_0004872 in vivo. RIP assay, biotin-coupled probe pull-down assay, FISH and luciferase reporter assay were performed to confirm the relationship between hsa_circ_0004872 and the identified miRNA. ChIP assay, luciferase reporter assay and western blot were used to determine the direct binding of Smad4 to the promoter of the ADAR1 gene. RESULTS: In this study, we found that hsa_circ_0004872 was dramatically downregulated in GC tissues compared with adjacent noncancerous tissues. The expression level of hsa_circ_0004872 was associated with tumor size and local lymph node metastasis. Enforced expression of hsa_circ_0004872 inhibited the proliferation, invasion and migration of GC cells, whereas knockdown of hsa_circ_0004872 had the opposite effects. Nude mice experiments showed that ectopic expression of hsa_circ_0004872 dramatically inhibited tumor growth and metastasis in vivo. Moreover, we demonstrated that hsa_circ_0004872 acted as a "molecular sponge" for miR-224 to upregulate the expression of the miR-224 downstream targets p21 and Smad4. Importantly, we found that the RNA-editing enzyme ADAR1 inhibited hsa_circ_0004872 expression and further led to the upregulation of miR-224. Smad4, the downstream target of miR-224, could further affect hsa_circ_0004872 levels by directly binding to the promoter region of ADAR1 to inhibit ADAR1 expression. CONCLUSIONS: Our findings showed that hsa_circ_0004872 acted as a tumor suppressor in GC by forming a negative regulatory loop consisting of hsa_circ_0004872/miR-224/Smad4/ADAR1. Thus, hsa_circ_0004872 may serve as a potential biomarker and therapeutic target for GC.