Fig. 1: Matrix stiffness is correlated with chemoresistance and poor survival in patients with breast cancer.

a The lesions of patients with breast cancer in the NAC cohort were evaluated by UE before and after neoadjuvant chemotherapy. Additionally, the pre-treatment biopsies and paired post-treatment resected samples were assessed by HE staining, picrosirius red staining, AFM, and immunofluorescence analysis. Representative images of ultrasound B-mode, UE, HE, picrosirius red staining, AFM map (inserted in picrosirius red pictures), and TUNEL/CK staining are shown (n = 124 patients). White dashed lines represent tumor outlines. Green and yellow squares in the HE pictures indicate the area shown in the picrosirius red and immunofluorescence pictures, respectively. Asterisks (*) indicate ___location of higher magnification views in TUNEL/CK staining images. Picrosirius red staining viewed under polarized light taken from breast cancer tissues reveal the fibrillar collagen in the ECM; AFM indentations are represented as a force heat map. b Quantification of tumor elastic scores in patients as (a) in the NAC cohort. Patients with CR or PR were classified as chemosensitive patients (n = 83 patients), while those with SD or PD were classified as chemoresistant ones (n = 41 patients). *p = 0.0237, ****p < 0.0001, by unpaired two-tailed Fisher exact probability test. c Quantification of tumor strain ratio in patients as (a). Mean ± SEM, ****p < 0.0001 by two-tailed Mann-Whitney U test. d Quantification of apoptotic tumor cells (TUNEL⁺CK⁺) in breast cancer samples obtained from patients of post-neoadjuvant chemotherapy. N = 83 for chemosensitive patients and n = 41 for chemoresistant patients. Mean ± SEM, ****p < 0.0001 by two-tailed Mann-Whitney U test. e, f Kaplan-Meier curves for DFS or OS of breast cancer patients with soft (strain ratio ≤ 8.7, n = 260 patients) or stiff (strain ratio > 8.7, n = 128 patients) matrix in the treatment-naive cohort. g, h The Kaplan–Meier plot for DFS (g) and OS (h) of patients with different subtypes in the treatment-naive cohort. HR⁺HER2^-, n = 216 patients; HR⁺HER2⁺, n = 78 patients; HR^-HER2⁺, n = 38 patients; HR^-HER2^-, n = 56 patients. For e–h P values were determined by log-rank test and shown in the figure.