HER2 is a prognostic and predictive biomarker in breast cancer, normally assessed in tumour biopsy and used to guide treatment choices. Circulating tumour cells (CTCs) escape the primary tumour and enter the bloodstream, exhibiting great metastatic potential and representing a real-time snapshot of the tumour burden. Liquid biopsy offers the unique opportunity for low invasive sampling in cancer patients and holds the potential to provide valuable information for the clinical management of cancer patients. This study assesses the performance of the RUBYchip™, a microfluidic system for CTC capture based on cell size and deformability, and compares it with the only FDA-approved technology for CTC enumeration, CellSearch^®. After optimising device performance, 30 whole blood samples from metastatic breast cancer patients were processed with both technologies. The expression of HER2 was assessed in isolated CTCs and compared to tissue biopsy. Results show that the RUBYchip^TM was able to isolate CTCs with higher efficiency than CellSearch^®, up to 10 times more, averaging all samples. An accurate evaluation of different CTC subpopulations, including HER2+ CTCs, was provided. Liquid biopsy through the use of the RUBYchip^TM in the clinic can overcome the limitations of histological testing and evaluate HER2 status in patients in real-time, helping to tailor treatment during disease evolution.

Renal cell carcinoma (RCC) presents as metastatic disease in one third of cases. Research on circulating tumor cells (CTCs) and liquid biopsies is improving the understanding of RCC biology and metastases formation. However, a standardized, sensitive, specific, and cost-effective CTC detection technique is lacking. The use of platforms solely relying on epithelial markers is inappropriate in RCC due to the frequent epithelial-mesenchymal transition that CTCs undergo. This study aimed to test and clinically validate RUBYchip™, a microfluidic label-free CTC detection platform, in RCC patients. The average CTC capture efficiency of the device was 74.9% in spiking experiments using three different RCC cell lines. Clinical validation was performed in a cohort of 18 patients, eight non-metastatic (M0), five metastatic treatment-naïve (M1TN), and five metastatic progressing-under-treatment (M1TP). An average CTC detection rate of 77.8% was found and the average (range) total CTC count was 6.4 (0–27), 101.8 (0–255), and 3.2 (0–10), and the average mesenchymal CTC count (both single and clustered cells) was zero, 97.6 (0–255), and 0.2 (0–1) for M0, M1TN, and M1TP, respectively. CTC clusters were detected in 25% and 60% of M0 and M1TN patients, respectively. These results show that RUBYchip™ is an effective CTC detection platform in RCC.

The combination of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) with endocrine therapy (ET) is the standard-of-care for estrogen receptor (ER)-positive, HER2-negative (ER+/HER2− advanced/metastatic breast cancer (mBC). However, the impact of CDK4/6i on circulating immune cells and circulating tumor cells (CTCs) in patients receiving CDK4/6i and ET (CDK4/6i+ET) remains poorly understood. This was a prospective cohort study including 44 patients with ER+/HER2− mBC treated with CDK4/6i+ET in either first or second line. Peripheral blood samples were collected before (baseline) and 3 months (t2) after therapy. Immune cell’s subsets were quantified by flow cytometry, and microfluidic-captured CTCs were counted and classified according to the expression of cytokeratin and/or vimentin. Patients were categorized according to response as responders (progression-free survival [PFS] ≥ 6.0 months; 79.1%) and non-responders (PFS < 6.0 months; 20.9%). CDK4/6i+ET resulted in significant changes in the hematological parameters, including decreased hemoglobin levels and increased mean corpuscular volume, as well as reductions in neutrophil, eosinophil, and basophil counts. Specific immune cell subsets, such as early-stage myeloid-derived suppressor cells, central memory CD4+ T cells, and Vδ2+ T cells expressing NKG2D, decreased 3 months after CDK4/6i+ET. Additionally, correlations between the presence of CTCs and immune cell populations were observed, highlighting the interplay between immune dysfunction and tumor dissemination. This study provides insights into the immunomodulatory effects of CDK4/6i+ET, underscoring the importance of considering immune dynamics in the management of ER+/HER2− mBC.

Despite chemotherapy’s limitations and toxic effects, it remains the primary treatment for most patients with triple-negative breast cancer (TNBC), with or without immune checkpoint inhibitors. Although cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) combined with endocrine therapy have revolutionized luminal breast cancer treatment, CDK4/6is alone are largely ineffective in TNBC, even with functional retinoblastoma protein (pRB). Activation of the receptor activator of nuclear factor κB (RANK) pathway has been associated with poor prognosis in TNBC and with resistance to CDK4/6is in luminal breast cancer, effects that can be reversed by RANK ligand inhibitors (RANKLi). In this study, we analyzed the effect of RANK knockdown or RANKLi in the response of pRB-proficient TNBC to CDK4/6i in vitro. RANK + patient-derived xenograft and cell line–derived xenograft models were used to assess therapeutic efficacy of CDK4/6i + RANKLi in vivo. Two syngeneic models of TNBC and luminal breast cancer were used to portrait the main therapy-induced alterations in the tumor immune microenvironment. RANK knockdown or RANKLi sensitized pRB-proficient TNBC cells to CDK4/6i in vitro. The combination of palbociclib and RANKLi regressed or prevented tumor growth and metastasis in vivo, enhancing cell cycle arrest. Both CDK4/6i and RANKLi elicited an antitumor immune response, characterized by an increase in CD4+ and CD8+ T cells and a decrease in tumor-associated macrophages infiltrating the tumor microenvironment. These findings suggest that combining CDK4/6i and RANKLi could offer a new therapeutic strategy for pRB-proficient TNBC, holding potential immunomodulatory benefits across breast cancer subtypes.

Undifferentiated pleomorphic sarcoma (UPS) remains one of the most clinically aggressive and poorly characterized soft-tissue sarcoma subtypes. To uncover distinctive molecular traits for UPS, a multiomics analysis of UPS compared with leiomyosarcoma (LMS) and liposarcoma (LPS) was performed. Transcriptomic profiling revealed that UPS exhibits overexpression of genes encoding succinate dehydrogenase (SDH) subunits, particularly SDHB, SDHC, and SDHD, distinguishing it from LMS and dedifferentiated LPS. This finding was validated using The Cancer Genome Atlas Sarcoma dataset. High SDHB expression in UPS was significantly associated with shorter overall survival, shorter recurrence-free survival, and shorter overall survival from the date of first metastasis. IHC validated elevated SDHB protein levels in UPS and LMS relative to dedifferentiated LPS. Despite overexpression of SDH subunits, metabolomic profiling demonstrated a significantly higher succinate-to-fumarate ratio in UPS, suggesting functional impairment of SDH enzymatic activity potentially due to posttranslational modifications, altered assembly of SDH subunits, or imbalanced tricarboxylic acid flux. This paradoxical phenotype of SDH overexpression with enzymatic dysfunction defines a unique molecular and metabolic subtype of UPS with prognostic significance. Recognition of this distinct SDH-associated molecular and metabolic phenotype provides insights into UPS pathogenesis, identifies a potential novel prognostic biomarker, and suggests a new avenue for metabolic-targeted therapy. Significance: This study identified a paradoxical phenotype of SDH subunit overexpression with functional impairment in UPS, defining a molecular/metabolic subtype associated with poor prognosis. It offers new data on UPS pathogenesis and treatment.