Integrin-associated transcriptional characteristics of circulating tumor cells in breast cancer patients.

Background: Integrins enable cell communication with the basal membrane and extracellular matrix, activating signaling pathways and facilitating intracellular changes. Integrins in circulating tumor cells (CTCs) play a significant role in apoptosis evasion and anchor-independent survival. However, the link between CTCs expressing different integrin subunits, their transcriptional profile and, therefore, their functional activity with respect to metastatic potential remains unclear. Methods: Single-cell RNA sequencing of CD45-negative cell fraction of breast cancer patients was performed. All CTCs were divided into nine groups according to their integrin profile. Results: СTCs without the gene expression of integrins or with the expression of non-complementary α and ß subunits that cannot form heterodimers prevailed. Only about 15% of CTCs expressed integrin subunits which can form heterodimers. The transcriptional profile of CTCs appeared to be associated with the spectrum of expressed integrins. The lowest potential activity was observed in CTCs without integrin expression, while the highest frequency of expression of tumor progression-related genes, namely genes of stemness, epithelial-mesenchymal transition (EMT), invasion, proinflammatory chemokines and cytokines as well as laminin subunits, were observed in CTCs co-expressing ITGA6 and ITGB4. Validation on the protein level revealed that the median of integrin ß4+ CTCs was higher in patients with more aggressive molecular subtypes as well as in metastatic breast cancer patients. One can expect that CTCs with ITGA6 and ITGB4 expression will have pronounced metastatic potencies manifesting in expression of EMT and stemness-related genes, as well as potential ability to produce chemokine/proinflammatory cytokines and laminins.

Spatial Heterogeneity of Integrins and Their Ligands in Primary Breast Tumors.

BACKGROUND: The diversity of cell-cell interactions in different regions of a tumor reflects the functional heterogeneity of cancer, which poses challenges in early diagnosis, selection of treatment strategies, and prognosis of breast cancer. Cancer cells interact with each other to form different morphological structures in the tumor and stromal host cells via integrins. The objective of this study was to characterize the morphological and spatial heterogeneity of primary breast tumors in the context of expression profiles of integrins and their ligands. METHODS: We studied spatial transcriptomics using the 10X Visium approach and the Niche Interactions and Communication Heterogeneity in Extracellular Signaling (NICHES) algorithm to map ligand-receptor signaling pathways and visualize the heterogeneity of signaling archetypes in tumor clusters. RESULTS: Cluster analysis of the expression profiles of tumor spots from the samples indicated pronounced inter-tumoral heterogeneity. Integrin-ligand functional clusters were associated with intratumoral heterogeneity, which was manifested by the presence of several morphological loci as observed in histological tumor samples. Inter-tumoral heterogeneity was manifested by a different number of functional clusters, ranging from 2 to 9 for each tumor sample. The main characteristic of these clusters was the significant predominance of non-complementary integrin subunits. Of the 42 functional integrin-ligand pairs in 21 clusters of five samples, 41 pairs occurred only once. The exception was the laminin subunit alpha-5 (LAMA5)-integrin beta 4 (ITGB4) pair, which was detected in two clusters of different samples. CONCLUSIONS: The spatial heterogeneity of integrin-ligand expression clusters in breast cancer contributes significantly to the functional heterogeneity of the tumor, which sets the stage for many scenarios of parenchymatous-stromal relationships, some of which may be effective in the emergence of metastasizing tumor seed cells. The intra- and inter-tumoral spatio-functional heterogeneity of the tumor tissue that we discovered may largely explain why it is difficult to achieve success in most patients with breast cancer using any therapeutic strategy targeting one molecule of the vast array, regardless of the importance of its pathogenetic significance.

Heterogeneity of Circulating Epithelial Cells in Breast Cancer at Single-Cell Resolution: Identifying Tumor and Hybrid Cells.

Circulating tumor cells and hybrid cells formed by the fusion of tumor cells with normal cells are leading players in metastasis and have prognostic relevance. This study applies single-cell RNA sequencing to profile CD45-negative and CD45-positive circulating epithelial cells (CECs) in nonmetastatic breast cancer patients. CECs are represented by transcriptionally-distinct populations that include both aneuploid and diploid cells. CD45- CECs are predominantly aneuploid, but one population contained more diploid than aneuploid cells. CD45+ CECs mostly diploid: only two populations have aneuploid cells. Diploid CD45+ CECs annotated as different immune cells, surprisingly harbored many copy number aberrations, and positively correlated to tumor grade. It is noteworthy that cancer-associated signaling pathways areabundant only in one aneuploid CD45- CEC population, which may represent an aggressive subset of circulating tumor cells. Thus, CD45- and CD45+ CECs are highly heterogeneous in breast cancer patients and include aneuploid cells, which are most likely circulating tumor and hybrid cells, respectively, and diploid cells. DNA ploidy analysis can be an effective instrument for identifying tumor and hybrid cells among CECs. Further follow-up study is needed to determine which subsets of circulating tumor and hybrid cells contribute to breast cancer metastasis.

LIMCH1 as a New Potential Metastasis Predictor in Breast Cancer.

BACKGROUND AND OBJECTIVE: High LIMCH1 expression in lung and renal cancer is determined as a favorable prognostic factor. However, prognostic value of LIMCH1 expression in breast cancer has not been studied yet. Therefore, this study was performed to determine the prognostic value of LIMCH1 expression in breast cancer patients. METHODS: This retrospective study included 89 patients with invasive breast carcinoma of no special type. These patients referred to  Cancer Research Institute of Tomsk National Research Medical Center from 2007 to 2018. LIMCH1 protein expression in tumor cells was detected by immunohistochemical analysis in this study. Statistical analysis was done to investigate the possible relationship between LIMCH1 protein expression and clinicopathological parameters, risk of metastasis, distant metastasis free survival, and overall survival. RESULTS: IHC analysis of breast cancer tissue samples revealed that LIMHC1 protein expression was found in 29.2% (26/89) of the cases. Lymph node and distant metastases were more frequent in patients with LIMCH1 protein expression. LIMCH1 protein expression increased the risk of distant metastasis based on our findings. LIMCH1 protein affected metastatic-free survival regardless of the T, as well as other clinical and pathological parameters (p=0.0146, HR=3.2058 (1.26; 8.17)). Moreover, LIMCH1 protein expression was associated with worse overall survival (p=0.0071, HR=2.73 (1.28; 5.85)) in our breast cancer patients. CONCLUSION: LIMCH1 protein expression was associate with metastases development, providing prognostic stratification. In breast cancer, LIMCH1 protein expression was found as an unfavorable prognostic factor of distant metastasis-free survival based on our findings.

The Novel Association of Early Apoptotic Circulating Tumor Cells with Treatment Outcomes in Breast Cancer Patients.

Stemness and epithelial-mesenchymal plasticity are widely studied in the circulating tumor cells of breast cancer patients because the roles of both processes in tumor progression are well established. An important property that should be taken into account is the ability of CTCs to disseminate, particularly the viability and apoptotic states of circulating tumor cells (CTCs). Recent data demonstrate that apoptosis reversal promotes the formation of stem-like tumor cells with pronounced potential for dissemination. Our study focused on the association between different apoptotic states of CTCs with short- and long-term treatment outcomes. We evaluated the association of viable CTCs, CTCs with early features of apoptosis, and end-stage apoptosis/necrosis CTCs with clinicopathological parameters of breast cancer patients. We found that the proportion of circulating tumor cells with features of early apoptosis is a perspective prognosticator of metastasis-free survival, which also correlates with the neoadjuvant chemotherapy response in breast cancer patients. Moreover, we establish that apoptotic CTCs are associated with the poor response to neoadjuvant chemotherapy, and metastasis-free survival expressed at least two stemness markers, CD44 and CD133.