Autophagy induced by a sulphamoylated estrone analogue contributes to its cytotoxic effect on breast cancer cells

Antiproliferation and apoptosis studies of estrone pharmacophores in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that shows high metastatic capability and poor prognosis. The aggressive behavior of TNBC may involve amplified EGFR expression. Currently, no targeted therapy has been approved for treating TNBC, which urgently needs novel treatment options. In this study, we report that estrone analogs with novel pharmacophores exhibited high potency toward TNBC cells through multiple mechanisms, inhibition of cell proliferation via EGFR receptor, and induction of mitochondrial apoptosis. Molecular docking studies revealed that hit analogs MMA307 and MMA321 were potent against the EGFR receptor (pdb code: 1M17) in silico and were over 10-fold more potent than sorafenib (positive control) when dosed against MDA-MB-468 cells in vitro. MMA307 and MMA321 induced mitochondrial apoptosis as characterized by condensed nuclei with fragmented chromatin, phosphatidylserine flip and modulated expressions of Apaf1, cytochrome c, and caspases 3 and 9. MMA307 and MMA321 inhibited TNBC proliferation through suppression of EGFR and activated EGFR (Y1068) expressions. Similarly, EGFR signaling pathways, RAF/ERK and AKT/mTOR, were inhibited as pARaf, pERK1/2 (characterizes RAF/ERK pathway) and pAKT, pmTOR, p70S6Kα (characterizes AKT/mTOR pathway) were all suppressed. Moreover, MMA307 and MMA321 inhibited TNBC cell growth through downregulation of cyclin D1 expression and arresting TNBC cells in the G1 phase of cell cycle. This study reports for the first time that estrone congeners with novel pharmacophores may be an effective therapy for TNBC. Findings from this research provide a solid foundation for further preclinical and clinical studies in developing estrone derivatives as novel TNBC therapeutics.

Vitamin D3/VDR inhibits inflammation through NF-κB pathway accompanied by resisting apoptosis and inducing autophagy in abalone Haliotis discus hannai

Vitamin D3 is believed to be a contributing factor to innate immunity. Vitamin D receptor (VDR) has a positive effect on inhibiting nuclear factor κB (NF-κB)-mediated inflammation. The underlying molecular mechanisms remain unclear, particularly in mollusks. Consequently, this study will investigate the process of vitamin D3/VDR regulating NF-κB pathway and further explore their functions on inflammation, autophagy, and apoptosis in abalone Haliotis discus hannai. Results showed that knockdown of VDR by using siRNA and dsRNA of VDR in vitro and in vivo led to more intense response of NF-κB signaling to lipopolysaccharide and higher level of apoptosis and autophagy. In addition, 1,25(OH)2D3 stimulation after VDR silencing could partially alleviate apoptosis and induce autophagy. Overexpression of VDR restricted the K48-polyubiquitin chain-dependent inhibitor of κB (IκB) ubiquitination and apoptosis-associated speck-like protein containing CARD (ASC) oligomerization. Besides, VDR silencing resulted in increase of ASC speck formation. In further mechanistic studies, we showed that VDR can directly bind to IκB and IKK1 in vitro and in vivo. In the feeding trial, H&E staining, TUNEL, and electron microscope results showed that vitamin D3 deficiency (0 IU/kg) could recruit more basophilic cells and increase more TUNEL-positive apoptotic cells and lipid droplets (LDs) than vitamin D3 supplement (1000 IU/kg and 5000 IU/kg). In summary, abalone VDR plays a negative regulator role in NF-κB-mediated inflammation via interacting with IκB and inhibiting ubiquitin-dependent degradation of IκB. Vitamin D3 in combination with VDR is essential to establish a delicate balance between autophagy and apoptosis in response to inflammation.

Radiosensitization of Breast Cancer Cells with a 2-Methoxyestradiol Analogue Affects DNA Damage and Repair Signaling In Vitro

Radiation resistance and radiation-related side effects warrant research into alternative strategies in the application of this modality to cancer treatment. Designed in silico to improve the pharmacokinetics and anti-cancer properties of 2-methoxyestradiol, 2-ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) disrupts microtubule dynamics and induces apoptosis. Here, we investigated whether pre-exposure of breast cancer cells to low-dose ESE-16 would affect radiation-induced deoxyribonucleic acid (DNA) damage and the consequent repair pathways. MCF-7, MDA-MB-231, and BT-20 cells were exposed to sub-lethal doses of ESE-16 for 24 h before 8 Gy radiation. Flow cytometric quantification of Annexin V, clonogenic studies, micronuclei quantification, assessment of histone H2AX phosphorylation and Ku70 expression were performed to assess cell viability, DNA damage, and repair pathways, in both directly irradiated cells and cells treated with conditioned medium. A small increase in apoptosis was observed as an early consequence, with significant repercussions on long-term cell survival. Overall, a greater degree of DNA damage was detected. Moreover, initiation of the DNA-damage repair response was delayed, with a subsequent sustained elevation. Radiation-induced bystander effects induced similar pathways and were initiated via intercellular signaling. These results justify further investigation of ESE-16 as a radiation-sensitizing agent since pre-exposure appears to augment the response of tumor cells to radiation.

DNA damage response and breast cancer development: Possible therapeutic applications of ATR, ATM, PARP, BRCA1 inhibition

Breast cancer is the most common and significant cancers in females regarding the loss of life quality. Similar to other cancers, one of the etiologic factors in breast cancer is DNA damage. A plethora of molecules are responsible for sensing DNA damage and mediating actions which lead to DNA repair, senescence, cell cycle arrest and if damage is unbearable to apoptosis. In each of these, aberrations leading to unrepaired damage was resulted in uncontrolled proliferation and cancer. Another cellular function is autophagy defined as a process eliminating of unnecessary proteins in stress cases involved in pathogenesis of cancer. Knowing their role in cancer, scholars have tried to develop strategies in order to target DDR and autophagy. Further, the interactions of DDR and autophagy plus their regulatory role on each other have been focused simultaneously. The present review study has aimed to illustrate the importance of DDR and autophagy in breast cancer according to the related studies and uncover the relation between DDR and autophagy and its significance in breast cancer therapy.

Depletion of membrane cholesterol compromised caspase-8 imparts in autophagy induction and inhibition of cell migration in cancer cells

Background

Cholesterol in lipid raft plays crucial role on cancer cell survival during metastasis of cancer cells. Cancer cells are reported to enrich cholesterol in lipid raft which make them more susceptible to cell death after cholesterol depletion than normal cells. Methyl-β-cyclodextrin (MβCD), an amphipathic polysaccharide known to deplete the membrane cholesterol, induces cell death selectively in cancer cells. Present work was designed to identify the major form of programmed cell death in membrane cholesterol depleted cancer cells (MDA-MB 231 and 4T1) and its impact on migration efficiency of cancer cells.

Methods

Membrane cholesterol alteration and morphological changes in 4T1 and MDA-MB 231 cancer cells by MβCD were measured by fluorescent microscopy. Cell death and cell proliferation were observed by PI, AO/EB and MTT assay respectively. Programme cell death was confirmed by flow cytometer. Caspase activation was assessed by MTT and PI after treatments with Z-VAD [OME]-FMK, mitomycin c and cycloheximide. Necroptosis, autophagy, pyroptosis and paraptosis were examined by cell proliferation assay and flow cytometry. Relative quantitation of mRNA of caspase-8, necroptosis and autophagy genes were performed. Migration efficiency of cancer cells were determined by wound healing assay.

Results

We found caspase independent cell death in cholesterol depleted MDA-MB 231 cells which was reduced by (3-MA) an autophagy inhibitor. Membrane cholesterol depletion neither induces necroptosis, paraptosis nor pyroptosis in MDA-MB 231 cells. Subsequent activation of caspase-8 after co-incubation of mitomycin c and cycloheximide separately, restored the cell viability in cholesterol depleted MDA-MB 231 cells. Down regulation of caspase-8 mRNA in cholesterol depleted cancer cells ensures that caspase-8 indirectly promotes the induction of autophagy. In another experiment we have demonstrated that membrane cholesterol depletion reduces the migration efficiency in cancer cells.

Conclusion

Together our experimental data suggests that membrane cholesterol is the crucial for the recruitment and activation of caspase-8 as well as its non-apoptotic functions in cancer cells. Enriched cholesterol in lipid raft of cancer cells may be regulating the cross talk between caspase-8 and autophagy machineries to promote their survival and migration. Therefore it can be explored to understand and address the issues of chemotherapeutic and drugs resistance.