Tumor metastasis remains the main cause of breast cancer-related deaths, especially delayed breast cancer distant metastasis. The current study assessed the frequency of CD44-/CD24- breast cancer cells in 576 tissue specimens for associations with clinicopathological features and metastasis and investigated the underlying molecular mechanisms. The results indicated that higher frequency (≥19.5%) of CD44-/CD24- cells was associated with delayed postoperative breast cancer metastasis. Furthermore, CD44-/CD24- triple negative breast cancer (TNBC) cells spontaneously converted into CD44+/CD24- cancer stem cells (CSCs) with properties similar to CD44+/CD24- CSCs from primary human breast cancer cells and parental TNBC cells in terms of stemness marker expression, self-renewal, differentiation, tumorigenicity and lung metastasis in vitro and in NOD/SCID mice. RNA sequencing identified several differentially expressed genes (DEGs) in newly converted CSCs and RHBDL2, one of the DEGs, expression was up-regulated. More importantly, RHBDL2 silencing inhibited the YAP1/USP31/NF-κB signaling and attenuated spontaneous CD44-/CD24- cell conversion into CSCs and their mammosphere formation. These findings suggest that the frequency of CD44-/CD24- tumor cells and RHBDL2 may be valuable for prognosis of delayed breast cancer metastasis, particularly for TNBC.
All data generated or analysed during this study are included in the manuscript and supporting files.
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: The experimental protocol was approved by the Animal Research and Care Committee of China Medical University (Shenyang, China) and followed the Guidelines of the Care and Use of Laboratory Animals issued by the Chinese Council on Animal Research. Female BALB/c nude mice (6 weeks old) were obtained from Human Silaikejingda Laboratory Animals (Changsha, China) and housed in a specific pathogen-free facility with free access to autoclaved food and water. All surgery was performed under sodium pentobarbital anesthesia, and every effort was made to minimize suffering. The current study was approved by the Ethics Committee of all three hospital review board review boards ((Project identification code: Project identification code: 2018PS304K, date on 03/05/2018 2018PS304K, date on 03/05/2018))
© 2021, Qiao et al.
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Cell crowding causes high-grade breast cancer cells to become more invasive by activating a molecular switch that causes the cells to shrink and spread.
Cell crowding is a common microenvironmental factor influencing various disease processes, but its role in promoting cell invasiveness remains unclear. This study investigates the biomechanical changes induced by cell crowding, focusing on pro-invasive cell volume reduction in ductal carcinoma in situ (DCIS). Crowding specifically enhanced invasiveness in high-grade DCIS cells through significant volume reduction compared to hyperplasia-mimicking or normal cells. Mass spectrometry revealed that crowding selectively relocated ion channels, including TRPV4, to the plasma membrane in high-grade DCIS cells. TRPV4 inhibition triggered by crowding decreased intracellular calcium levels, reduced cell volume, and increased invasion and motility. During this process, TRPV4 membrane relocation primed the channel for later activation, compensating for calcium loss. Analyses of patient-derived breast cancer tissues confirmed that plasma membrane-associated TRPV4 is specific to high-grade DCIS and indicates the presence of a pro-invasive cell volume reduction mechanotransduction pathway. Hyperosmotic conditions and pharmacologic TRPV4 inhibition mimicked crowding-induced effects, while TRPV4 activation reversed them. Silencing TRPV4 diminished mechanotransduction in high-grade DCIS cells, reducing calcium depletion, volume reduction, and motility. This study uncovers a novel pro-invasive mechanotransduction pathway driven by cell crowding and identifies TRPV4 as a potential biomarker for predicting invasion risk in DCIS patients.