Release of exosomes have been shown to play critical roles in drug resistance by delivering cargo. Targeting the transfer of exosomes from resistant cells to sensitive cells may be an approach to overcome some cases of drug resistance. In this study, we investigated the potential role of exosomes in the process of psoralen reverse multidrug resistance of MCF-7/ADR cells. Exosomes were isolated by differential centrifugation of culture media from MCF-7/ADR cells (ADR/exo) and MCF-7 parental cells (S/exo). Exosomes were characterized by morphology, exosomal markers and size distribution. The ability of ADR/exo to transfer multidrug resistance was assessed by MTT and real-time quantitative PCR. The different formation and secretion of exosomes were detected by immunofluorescence and transmission electron microscopy. Then we performed comparative transcriptomic analysis using RNA-Seq technology and real-time quantitative PCR to better understand the gene expression regulation in exosmes formation and release after psoralen treatment. Our data showed that exosomes derived from MCF-7/ADR cells were able to promote active sequestration of drugs and could induce a drug resistance phenotype by transferring drug-resistance-related gene MDR-1 and P-glycoprotein protein. Psoralen could reduce the formation and secretion of exosomes to overcome drug resistance. There were 21 differentially expressed genes. Gene ontology (GO) pathway analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the most significantly expressed genes were linked to PPAR and P53 signaling pathways which were related to exosomes formation, secretion and cargo sorting. Psoralen can affect the exosomes and induce the reduction of resistance transmission via exosomes might through PPAR and P53 signaling pathways, which might provide a novel strategy for breast cancer resistance to chemotherapy in the future.

Exosomes secreted from tumor cells can remodel the tumor environment by promoting tumor metastasis and multidrug resistance. The aim of this study was to analyze the proteome profile of the breast cancer line resistant to doxorubicin resistance (MCF-7/ADR) by liquid chromatography linked to tandem mass spectrometry assay (LC-MS/MS). Our results revealed that DOX increases the exosomes release from MCF-7/ADR cells and the exosome-mediated proteins intercellular transfer in breast cancer chemoresistance regulation. The expression of the candidate target exosomic CD44 in DOX-resistant cells (A/Exo) was higher than in parental breast cancer cells (S/Exo), and the increasing levels of exosomic CD44 (21.65-fold) were higher than those of cellular CD44 (6.55-fold) (all p < 0.05). Similar results were obtained in clinical samples; exosomal CD44 in the serum of nonresponders was significantly higher than that in the chemotherapy-responsive group (p < 0.05). Also, we modified the MCF-7–derived exosomes loaded with siRNA against CD44 to observe the effects of targeting reduced CD44 expression in luminal A breast cancer cells. Exosome-siRNA targeted CD44 (Exos-siCD44) could efficiently silence its expression. When cocultured on Exos-siCD44, breast cancer cells exhibited reduced cell proliferation and enhanced susceptibility to DOX. The same phenomenon was observed in mice. In conclusion, breast cancer cells could spread resistance capacity by the intercellular transfer of proteins, especially CD44, via exosomes.

Psoralen could inhibit the proliferation of human breast cancer cells, however, the molecular mechanism was unclear. We evaluated the anti-proliferative effects of psoralen by MTT, plate colony formation assay and cell cycle analysis in MCF-7 and MDA-MB-231 cells. The effects of psoralen on activation of Wnt/β-catenin and the related target genes were examined by quantitative real-time PCR, western blotting and cell immunofluorescence. The tumor growth was conducted in BALB/c nude mice and the pathological changes of heart, liver and kidney were also observed. Our results demonstrate that psoralen significantly inhibited cell proliferation by inducing G0/G1 phase arrest in MCF-7 cells and G2/M phase arrest in MDA-MB-231 cells. The expression of Fra-1 was reduced and Axin2 was promoted both in MCF-7 and MDA-MB-231 cells after psoralen treatment. The cytoplasmic accumulation and nuclear translocation of β-catenin were significantly reduced by psoralen. Psoralen increased the levels of phospho-(Y142) β-catenin, while decreased the expression of total β-catenin and its downstream target Fra-1 in vitro and vivo. Moreover, psoralen didn’t cause any significant toxicity at the effective concentration. Overall, our results might provide theoretical basis for clinical application of psoralen in breast cancer.

Breast cancer is a common malignant tumor in women. Ferroptosis, a programmed cell death pathway, is closely associated with breast cancer and its resistance. The transferrin receptor (TFRC) is a key factor in ferroptosis, playing a crucial role in intracellular iron accumulation and the occurrence of ferroptosis. This study investigates the influence and significance of TFRC and its upstream transcription factor hypoxia‐inducible factor‐1α (HIF1α) on the efficacy of neoadjuvant therapy in breast cancer. The differential gene obtained from clinical samples through genetic sequencing is TFRC. Bioinformatics analysis revealed that TFRC expression in breast cancer was significantly greater in breast cancer tissues than in normal tissues, but significantly downregulated in Adriamycin (ADR)‐resistant tissues. Iron‐responsive element‐binding protein 2 (IREB2) interacts with TFRC and participates in ferroptosis. HIF1α, an upstream transcription factor, positively regulates TFRC. Experimental results indicated higher levels of ferroptosis markers in breast cancer tissue than in normal tissue. In the TAC neoadjuvant regimen‐sensitive group, iron ion (Fe ²⁺ ) and malondialdehyde (MDA) levels were greater than those in the resistant group (all p < .05). Expression levels of TFRC, IREB2, FTH1, and HIF1α were higher in breast cancer tissue compared to normal tissue. Additionally, the expression of the TFRC protein in the TAC neoadjuvant regimen‐sensitive group was significantly higher than that in the resistant group (all p < .05), while the difference in the level of expression of IREB2 and FTH1 between the sensitive and resistant groups was not significant ( p > .05). The dual‐luciferase assay revealed that HIF1α acts as an upstream transcription factor of TFRC ( p < .05). Overexpression of HIF1α in ADR‐resistant breast cancer cells increased TFRC, Fe ²⁺ , and MDA content. After ADR treatment, the cell survival rate decreased significantly, and ferroptosis could be reversed by the combined application of Fer‐1 (all p < .05). In conclusion, ferroptosis and chemotherapy resistance are correlated in breast cancer. TFRC is a key regulatory factor influenced by HIF1α and is associated with chemotherapy resistance. Upregulating HIF1α in resistant cells may reverse resistance by activating ferroptosis through TFRC overexpression.

Invasive micropapillary carcinoma (IMPC) of the breast represents a rare subtype of breast cancer, accounting for 1% to 2% of all breast cancers worldwide. Although clinically asymptomatic, they are usually detected during routine breast screenings. The common symptoms include breast lumps, skin or nipple changes, and nipple discharge. Histopathologically, IMPCs are characterized by tumor cells forming small papillary-like structures inside the glandular spaces, and arranged in an inverted pattern, with their apex pointing toward the center of the gland. This unique morphological feature is critical for diagnosing these cases. Another notable characteristic is its high propensity for lymph node metastasis (LNM). While the precise mechanism of metastasis is not clear, unique cellular arrangement and cellular interactions with the surrounding environment might promote tumorigenesis and higher node positivity. Hence, proper lymph node dissection and assessment are particularly crucial for this type of breast cancer. This review aims to discuss the recent progress in managing IMPC cases.