Poly (ADP-ribose) polymerase inhibitors (PARPis) are an exciting class of agents that have shown efficacy, particularly for BRCA-mutant triple-negative breast cancer (TNBC) and high-grade serous ov...

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) in combination with endocrine therapy are the standard treatment for patients with hormone receptor–positive, HER2–negative metastatic breast cancer (mBC). Despite the efficacy of CDK4/6is, intrinsic resistance occurs in approximately one-third of patients, highlighting the need for reliable predictive biomarkers. Methods: Single-cell RNA sequencing analyzed metastatic tumors from HR+/HER2- mBC patients pre-CDK4/6i treatment at baseline (BL) and/or at disease progression. BL samples were from CDK4/6i responders (median progression-free survival [mPFS] = 25.5 months), while progressors were categorized as early-progressors (EP, mPFS = 3 months) and late-progressors (LP, mPFS = 11 months). Metastatic sites included liver, pleural effusions, ascites, and bone. InferCNV distinguished tumor cells, and functional analysis utilized the Molecular Signatures Database. Results: LP tumors displayed enhanced Myc, EMT, TNF-α, and inflammatory pathways compared to those EP tumors. Samples from BL and LP responders showed increased tumor-infiltrating CD8⁺ T cells and natural killer (NK) cells compared to EP non-responders. Notably, despite a high frequency of CD8⁺ T cells in responding tumors, a functional analysis revealed significant upregulation of genes associated with stress and apoptosis in proliferative CD4⁺ and CD8⁺ T cells in BL tumors compared to in EP and LP tumors. These genes, including HSP90 and HSPA8, are linked to resistance to PD1/PD-L1 immune checkpoint inhibitors. A ligand-receptor analysis showed enhanced interactions associated with inhibitory T-cell proliferation (SPP1-CD44) and suppression of immune activity (MDK-NCL) in LP tumors. Longitudinal biopsies consistently revealed dynamic NK cell expansion and enhanced cytotoxic T cell activity, alongside upregulation of immune activity inhibition, in LP tumors compared to in BL tumors. Notably, the predictive biomarker panel from BL tumor cells was validated in 2 independent cohorts, where it consistently predicted a significant improvement in mPFS duration in signature-high versus -low groups. Conclusion: This study underscores the significance of molecular biomarkers in predicting clinical outcomes to CDK4/6i. Tumor-infiltration CD8⁺ T and NK cells may also serve as baseline predictors. These insights pave the way for optimizing therapeutic strategies based on microenvironment-specific changes, providing a personalized and effective approach for managing HR+/HER2- mBC and improving patient outcomes.

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) combined with endocrine therapy are the standard first-line treatment for hormone receptor-positive, HER2−negative (HR+/HER2−) metastatic breast cancer, but resistance inevitably develops. In triple-negative breast cancer (TNBC), the efficacy of CDK4/6i remains uncertain. Our study shows that the selective CDK2 inhibitor BLU-222, while effective alone, enhances synergistic activity when combined with CDK4/6i in resistant HR+/HER2− and TNBC models, leading to increased apoptosis and cell cycle arrest. In vivo, combining BLU-222 with palbociclib or ribociclib produced significant antitumor activity across eight resistant models, driving durable tumor regression and prolonged survival. Mechanistically, BLU-222, alone or with palbociclib, upregulated p21 and p27 expression, enhanced p21 binding to CDK2 as well as p21 and p27 binding to CDK4. CRISPR knockout of p21 or p27 in palbociclib-resistant cells eliminated this synergy. Further, RNA sequencing revealed that combination treatment upregulated senescence and interferon pathways, providing mechanistic insight into the observed therapeutic synergy.

Insulin-like growth factor I (IGF-1) has been implicated in breast cancer due to its mitogenic and anti-apoptotic effects. Despite substantial research on the role of IGF-1 in tumor progression, the relationship of IGF-1 to tissue stem cells, particularly in mammary tissue, and the resulting tumor susceptibility has not been elucidated. Previous studies with the BK5.IGF-1 transgenic (Tg) mouse model reveals that IGF-1 does not act as a classical, post-carcinogen tumor promoter in the mammary gland. Pre-pubertal Tg mammary glands display increased numbers and enlarged sizes of terminal end buds, a niche for mammary stem cells (MaSCs). Here we show that MaSCs from both wild-type (WT) and Tg mice expressed IGF-1R and that overexpression of Tg IGF-1 increased numbers of MaSCs by undergoing symmetric division, resulting in an expansion of the MaSC and luminal progenitor (LP) compartments in pre-pubertal female mice. This expansion was maintained post-pubertally and validated by mammosphere assays in vitro and transplantation assays in vivo. The addition of recombinant IGF-1 promoted, and IGF-1R downstream inhibitors decreased mammosphere formation. Single-cell transcriptomic profiles generated from 2 related platforms reveal that IGF-1 stimulated quiescent MaSCs to enter the cell cycle and increased their expression of genes involved in proliferation, plasticity, tumorigenesis, invasion, and metastasis. This study identifies a novel, pro-tumorigenic mechanism, where IGF-1 increases the number of transformation-susceptible carcinogen targets during the early stages of mammary tissue development, and “primes” their gene expression profiles for transformation.

Diet is a critical environmental factor affecting breast cancer risk, and recent evidence shows that dietary exposures during early development can affect lifetime mammary cancer susceptibility. To elucidate the underlying mechanisms, we used our established crossover feeding mouse model, where exposure to a high-fat and high-sugar (HFHS) diet during defined developmental windows determines mammary tumor incidence and latency in carcinogen-treated mice. Mammary tumor incidence is significantly increased in mice receiving a HFHS post-weaning diet (high-tumor mice, HT) compared to those receiving a HFHS diet during gestation (low-tumor mice, LT). The current study revealed that the mammary stem cell (MaSC) population was significantly increased in mammary glands from HT compared to LT mice. Igf1 expression was increased in mammary stromal cells from HT mice, where it promoted MaSC self-renewal. The increased Igf1 expression was induced by DNA hypomethylation of the Igf1 Pr1 promoter, mediated by a decrease in Dnmt3b levels. Mammary tissues from HT mice also had reduced levels of Igfbp5, leading to increased bioavailability of tissue Igf1. This study provides novel insights into how early dietary exposures program mammary cancer risk, demonstrating that effective dietary intervention can reduce mammary cancer incidence.

Background: Previous studies demonstrate a reduced risk of thrombosis and mortality with anticoagulant treatment in patients with COVID-19 than in those without anticoagulation treatment. However, an open question regarding the efficacy and safety of therapeutic anticoagulation (T-AC) versus a lower dose, prophylaxis anticoagulation (P-AC) in COVID-19 patients is still controversial.Methods: We systematically reviewed currently available randomized clinical trials (RCTs) and observational studies (OBs) from January 8, 2019, to January 8, 2022, and compared prophylactic and therapeutic anticoagulant treatment in COVID-19 patients. The primary outcomes were risk of mortality, major bleeding, and the secondary outcomes included venous and arterial thromboembolism. Subgroup analysis was also performed between critically ill and non-critically ill patients with COVID-19 and between patients with higher and lower levels of D-dimer. Sensitivity analysis was performed to decrease the bias and the impact of population heterogeneity.Results: We identified 11 RCTs and 17 OBs fulfilling our inclusion criteria. In the RCTs analyses, there was no statistically significant difference in the relative risk of mortality between COVID-19 patients with T-AC treatment and those treated with P-AC (RR 0.95, 95% CI, 0.78–1.15,P = 0.60). Similar results were also found in the OBs analyses (RR 1.21, 95% CI, 0.98–1.49,P = 0.08). The pooling meta-analysis using a random-effects model combined with effect sizes showed that in the RCTs and OBs analyses, patients with COVID-19 who received T-AC treatment had a significantly higher relative risk of the major bleeding event than those with P-AC treatment in COVID-19 patients (RCTs: RR 1.76, 95% CI, 1.19–2.62,P = 0.005; OBs: RR 2.39, 95% CI, 1.56–3.68,P < 0.0001). Compared with P-AC treatment in COVID-19 patients, patients with T-AC treatment significantly reduced the incidence of venous thromboembolism (RR 0.51, 95% CI, 0.39–0.67,P<0.00001), but it is not associated with arterial thrombosis events (RR 0.97, 95% CI, 0.66–1.42,P = 0.87). The subgroup analysis of OBs shows that the mortality risk significantly reduces in critically ill COVID-19 patients treated with T-AC compared with those with P-AC treatment (RR 0.58, 95% CI, 0.39–0.86,P = 0.007), while the mortality risk significantly increases in non-critically ill COVID-19 patients treated with T-AC (RR 1.56, 95% CI, 1.34–1.80,P < 0.00001). In addition, T-AC treatment does not reduce the risk of mortality in COVID-19 patients with high d-dimer levels in RCTs. Finally, the overall sensitivity analysis after excluding two RCTs studies remains consistent with the previous results.Conclusions: In our integrated analysis of included RCTs and OBs, there is no significant difference between the mortality of T-AC and P-AC treatment in unselected patients with COVID-19. T-AC treatment in COVID-19 patients significantly reduced the incidence of venous thromboembolism but showed a higher risk of bleeding than those with P-AC treatment. In addition, P-AC treatment was superior to T-AC treatment in non-critically ill COVID-19 patients, the evidence supporting the necessity for T-AC treatment in critically ill COVID-19 patients came only from OBs.Trial registration: Protocol registration: The protocol was registered at PROSPERO (CRD42021293294).Graphical