Breast cancer has a poor prognosis owing to tumor cell invasion and metastasis. Although Ras homolog (Rho) A is involved in tumor cell invasion, its role in breast carcinoma is unclear. Here, RhoA expression was examined in invasive ductal carcinoma (IDC), with a focus on its relationships with epidermal-mesenchymal transition (EMT) and collective cell invasion. Forty-four surgical IDC tissue samples and two normal breast tissue samples were obtained. RhoA, E-cadherin, vimentin, and F-actin protein expression were analyzed by immunohistochemistry. RhoA, ROCK, mTOR, AKT1, and PIK3CA mRNA expression were conducted using laser microdissection and semi-nested quantitative reverse transcription-polymerase chain reaction. RhoA expression was stronger on the tumor interface of IDCs than the tumor center (P<0.001). RhoA expression was correlated with ROCK expression only in HER2-subtype IDC (P<0.05). In IDCs co-expressing RhoA and ROCK, F-actin expression was stronger on the tumor interface, particularly at the edges of tumor cells, than it was in ROCK-negative IDCs (P<0.0001). In conclusion, RhoA expression was not correlated with EMT in IDC, but enhanced F-actin expression was localized on the edge of tumor cells that co-expressed ROCK. RhoA/ROCK signaling may be associated with collective cell invasion, particularly in HER2-subtype IDC.

Neutrophil extracellular traps (NETs) released from dead neutrophils at the site of inflammation represent webs of neutrophilic DNA stretches dotted with granule-derived antimicrobial proteins, including lactoferrin, and play important roles in innate immunity against microbial infection. We have shown the coexistence of NETs and fibrin meshwork in varied fibrinopurulent inflammatory lesions at both light and electron microscopic levels. In the present study, correlative light and electron microscopy (CLEM) employing confocal laser scanning microscopy and scanning electron microscopy was performed to bridge light and electron microscopic images of NETs and fibrin fibrils in formalin-fixed, paraffin-embedded, autopsied lung sections of legionnaire’s pneumonia. Lactoferrin immunoreactivity and 4'-6-diamidino-2-phenylindole (DAPI) reactivity were used as markers of NETs, and fibrin was probed by fibrinogen gamma chain. Of note is that NETs light microscopically represented as lactoferrin and DAPI-colocalized dots, 2.5 μm in diameter. CLEM gave super-resolution images of NETs and fibrin fibrils: “Dotted” NETs were ultrastructurally composed of fine filaments and masses of 58 nm-sized globular materials. A fibrin fibril consisted of clusters of smooth-surfaced filaments. NETs filaments (26 nm in diameter) were significantly thinner than fibrin filaments (295 nm in diameter). Of note is that CLEM was applicable to formalin-fixed, paraffin-embedded sections of autopsy material.

We established an experimental system that can induce p53-dependent apoptosis by doxycycline treatment to analyze characteristics of the apoptosis-resistant cancer cell subpopulation in the human breast cancer cell line HCC1937. Expression patterns of the stem cell markers, ALDH1A3 and Sox-2, the luminal differentiation marker, GATA3 and the proliferation index marker, Ki-67 were analyzed using immunostaining and fluorescence-activated cell sorting (FACS). After doxycycline treatment, the number of viable cells was gradually decreased over seven days in a time-dependent manner due to p53-induced apoptosis; however, the number of smaller-sized ALDH1A3⁺ cells assessed by immunostaining increased sharply after 1 day of doxycycline treatment, suggesting their apoptosis-resistant nature. The expression of ALDH1A3 was also detected in 78% of small-sized Ki-67⁺ proliferating progenitor cells, followed by the transient expression of GATA3, which presumably indicated the ability to differentiate into luminal progenitor cells. Although 42.2–58.5% of residual cells were positive for both ALDH1A3 and GATA3, their expression patterns exhibited an inverse correlation. The expression pattern of another stem cell marker, Sox-2, was similar, but more drastically altered after p53 induction compared with ALDH1A3. These findings may aid in understanding the hierarchical responses of cancer stem cells to therapeutic stresses.