Cell Cycle Regulation in Treatment of Breast Cancer.

Cell cycle progression and cell proliferation are under precise and orchestrated control in normal cells. However, uncontrolled cell proliferation caused by aberrant cell cycle progression is a crucial characteristic of cancer. Understanding cell cycle progression and its regulation sheds light on cancer treatment. Agents targeting cell cycle regulators (such as CDKs) have been considered as promising candidates in cancer treatment. Although the first-generation pan-CDK inhibitors failed in clinical trials because of their adverse events and low efficacy, new selective CDK 4/6 inhibitors showed potent efficacy with tolerable safety in preclinical and clinical studies. Here we will review the mechanisms of cell cycle regulation and targeting key cell cycle regulators (such as CDKs) in breast cancer treatment. Particularly, we will discuss the mechanism of CDK inhibitors in disrupting cell cycle progression, the use of selective CDK4/6 inhibitors in treatment of advanced, hormone receptor (HR)-positive postmenopausal breast cancer patients, and other clinical trials that aim to extend the utilization of these agents.

Conservative medical intervention as a complement to CDT for BCRL therapy: a systematic review and meta-analysis of randomized controlled trials.

Background: The effect of first-line complex decongestive therapy (CDT) for breast cancer-related lymphedema (BCRL) depending on various factors forces patients to seek additional treatment. Therefore, this meta-analysis was conducted to evaluate the effect of different conservative medical interventions as a complement to CDT. This is the first meta-analysis that includes various kinds of conservative treatments as adjunctive therapy to get broader knowledge and improve practical application value, which can provide recommendations to further improve BCRL patients' health status. Methods: RCTs published before 18 December 2023 from PubMed, Embase, Cochrane Library, and Web of Science databases were searched. RCTs that compared the effects of conservative medical intervention were included. A random-effects or fixed-effects model was used based on the heterogeneity findings. Study quality was evaluated using the Cochrane risk of bias tool. Results: Sixteen RCTs with 690 participants were included, comparing laser therapy, intermittent pneumatic compression (IPC), extracorporeal shock wave therapy (ESWT), electrotherapy, ultrasound, diet or diet in combination with synbiotic supplement, traditional Chinese medicine (TCM), continuous passive motion (CPM), and negative pressure massage treatment (NMPT). The results revealed that conservative medical intervention as complement to CDT had benefits in improving lymphedema in volume/circumference of the upper extremity [SMD = -0.30, 95% CI = (-0.45, -0.15), P < 0.05, I 2 = 51%], visual analog score (VAS) for pain [SMD = -3.35, 95% CI (-5.37, -1.33), P < 0.05, I 2 = 96%], quality of life [SMD = 0.44, 95% CI (0.19, 0.69), P < 0.05, I 2 = 0], and DASH/QuickDASH [SMD = -0.42, 95% CI (-0.70, -0.14), P < 0.05, I 2 = 10%] compared with the control group. Subgroup analysis revealed that laser therapy and electrotherapy are especially effective (P < 0.05). Conclusion: Combining conservative medical interventions with CDT appears to have a positive effect on certain BCRL symptoms, especially laser therapy and electrotherapy. It showed a better effect on patients under 60 years old, and laser therapy of low to moderate intensity (5-24 mW, 1.5-2 J/cm2) and of moderate- to long-term duration (≥36-72 sessions) showed better effects. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=354824, identifier CRD42022354824.

Different dosage forms of gonadotropin-releasing hormone agonist with endocrine therapy in premenopausal hormone receptor-positive breast cancer.

BACKGROUND: Despite the wide use of a 3-month gonadotropin-releasing hormone (GnRH) agonist for ovarian function suppression in premenopausal breast cancer patients, it remains unclear whether it is as effective and safe as a 1-month GnRH agonist regimen when combined with selective estrogen receptor modulators or aromatase inhibitors, especially in younger patients. METHODS: This retrospective cohort study included 1109 premenopausal hormone receptor-positive breast cancer patients treated with GnRH agonist plus selective estrogen receptor modulator or aromatase inhibitor. The estradiol (E2) inhibition rate within 1-24 months after treatment with 1-month or 3-month GnRH agonist in cohorts and different subgroups was analyzed. RESULTS: Following 1:1 propensity score matching, 950 patients with a mean age of 39 years and a median follow-up of 46 months were included. Both the 1-month and 3-month groups achieved more than 90% E2 inhibition within 24 months (94.53% vs 92.84%, with a 95% confidence interval for the difference ranging from -4.78% to 1.41%), confirming the noninferiority of 3-month GnRH agonist. Both 1-month and 3-month GnRH agonist rapidly and consistently reduced E2 levels. Of the patients, 60 (6.3%) experienced incomplete ovarian function suppression, with similar rates in the 1-month and 3-month groups (5.5% vs 7.2%). Incomplete ovarian function suppression mainly occurred within the first 12 months, with age younger than 40 years and no prior chemotherapy being the risk factors. Similar disease-free survival and overall survival were found in the 1-month and 3-month groups and in patients with complete and incomplete ovarian function suppression (P > .05). CONCLUSIONS: The ovarian function suppression with 3-month GnRH agonist was not inferior to that with 1-month GnRH agonist, regardless of age or combination with a selective estrogen receptor modulator or an aromatase inhibitor.

LncRNA EILA promotes CDK4/6 inhibitor resistance in breast cancer by stabilizing cyclin E1 protein.

CDK4/6 inhibitors (CDK4/6i) plus endocrine therapy are now standard first-line therapy for advanced HR+/HER2- breast cancer, but developing resistance is just a matter of time in these patients. Here, we report that a cyclin E1-interacting lncRNA (EILA) is up-regulated in CDK4/6i-resistant breast cancer cells and contributes to CDK4/6i resistance by stabilizing cyclin E1 protein. EILA overexpression correlates with accelerated cell cycle progression and poor prognosis in breast cancer. Silencing EILA reduces cyclin E1 protein and restores CDK4/6i sensitivity both in vitro and in vivo. Mechanistically, hairpin A of EILA binds to the carboxyl terminus of cyclin E1 protein and hinders its binding to FBXW7, thereby blocking its ubiquitination and degradation. EILA is transcriptionally regulated by CTCF/CDK8/TFII-I complexes and can be inhibited by CDK8 inhibitors. This study unveils the role of EILA in regulating cyclin E1 stability and CDK4/6i resistance, which may serve as a biomarker to predict therapy response and a potential therapeutic target to overcome resistance.

Overexpressed Cyclin D1 and CDK4 proteins are responsible for the resistance to CDK4/6 inhibitor in breast cancer that can be reversed by PI3K/mTOR inhibitors.

CDK4/6 inhibitors are the standard treatment in advanced HR+/HER2- breast cancer patients. Nevertheless, the resistance to CDK4/6 inhibitors is inevitable and the strategies to overcome resistance are of great interest. Here, we show that the palbociclib-resistant breast cancer cells expressed significantly higher levels of Cyclin D1 and CDK4 proteins because of upregulated protein synthesis. Silencing Cyclin D1 or CDK4 led to cell cycle arrest while silencing Cyclin E1 or CDK2 restored the sensitivity to palbociclib. Furthermore, PI3K/mTOR pathway was hyper-activated in palbociclib-resistant cells, leading to more phosphorylated 4E-BP1 and higher levels of Cyclin D1 and CDK4 translation. Targeting PI3K/mTOR pathway with a specific PI3Kα inhibitor (BYL719) or an mTOR inhibitor (everolimus) reduced the protein levels of Cyclin D1 and CDK4, and restored the sensitivity to palbociclib. The tumor samples expressed significantly higher levels of Cyclin D1, CDK4, p-AKT and p-4E-BP1 after progression on palbociclib treatment. In conclusion, our findings suggest that overexpressed Cyclin D1 and CDK4 proteins lead to the resistance to CDK4/6 inhibitor and PI3K/mTOR inhibitors are able to restore the sensitivity to CDK4/6 inhibitors, which provides the biomarker and rationale for the combinational use of CDK4/6 inhibitors and PI3K/mTOR inhibitors after CDK4/6 inhibitor resistance in breast cancer.

LIN9 confers paclitaxel resistance in triple negative breast cancer cells by upregulating CCSAP.

LIN9 functions to regulate cell mitotic process. Dysregulation of LIN9 expression is associated with development of human cancers. In this study we assessed the association of LIN9 expression with paclitaxel resistance and clarified the underlying mechanisms for the first time. LIN9 expression in breast cancer tissues was retrieved from publicly available online databases and statistically analyzed. Human TNBC cell lines MDA-MB-231 and MDA-MB-468 and their corresponding paclitaxel-resistant sublines 231PTX and 468PTX were used to assess the expression of LIN9 by qRT-PCR and Western blot, cell growth by cell counting, cell viability by MTS assay, and cell apoptosis by flow cytometry. The data showed that high LIN9 expression in breast cancer patients receiving chemotherapy was related to poor overall survival (OS). LIN9 expression was upregulated in paclitaxel-resistant TNBC cells compared to their parental cells. Knockdown of LIN9 or treatment of paclitaxel-resistant TNBC cells with a bromo- and extra-terminal domain inhibitor (BETi) JQ1 which also decreased LIN9 expression enhanced the sensitivity of paclitaxel-resistant TNBC cells to paclitaxel. Mechanistically, decreased LIN9 in resistant cell lines reduced tumor cell viability, promoted multinucleated cells formation and induced tumor cell apoptosis, potentially by directly regulating microtubule-binding protein CCSAP. In conclusion, high LIN9 expression contributed to poor clinical outcomes and paclitaxel resistance in TNBC and BETi, targeting LIN9 expression, could be a reversible drug for PTX-resistant TNBC patients.

LncRNA DILA1 inhibits Cyclin D1 degradation and contributes to tamoxifen resistance in breast cancer.

Cyclin D1 is one of the most important oncoproteins that drives cancer cell proliferation and associates with tamoxifen resistance in breast cancer. Here, we identify a lncRNA, DILA1, which interacts with Cyclin D1 and is overexpressed in tamoxifen-resistant breast cancer cells. Mechanistically, DILA1 inhibits the phosphorylation of Cyclin D1 at Thr286 by directly interacting with Thr286 and blocking its subsequent degradation, leading to overexpressed Cyclin D1 protein in breast cancer. Knocking down DILA1 decreases Cyclin D1 protein expression, inhibits cancer cell growth and restores tamoxifen sensitivity both in vitro and in vivo. High expression of DILA1 is associated with overexpressed Cyclin D1 protein and poor prognosis in breast cancer patients who received tamoxifen treatment. This study shows the previously unappreciated importance of post-translational dysregulation of Cyclin D1 contributing to tamoxifen resistance in breast cancer. Moreover, it reveals the novel mechanism of DILA1 in regulating Cyclin D1 protein stability and suggests DILA1 is a specific therapeutic target to downregulate Cyclin D1 protein and reverse tamoxifen resistance in treating breast cancer.

Circulating Tumor DNA Predicts the Response and Prognosis in Patients With Early Breast Cancer Receiving Neoadjuvant Chemotherapy.

PURPOSE: Many patients with breast cancer still relapse after curative treatment. How to identify the ones with high relapse risk remains a critical problem. Circulating tumor DNA (ctDNA) has recently become a promising marker to monitor tumor burden. Whether ctDNA can be used to predict the response and prognosis in patients with breast cancer receiving neoadjuvant chemotherapy (NAC) is unknown. Our study aimed to evaluate the clinical value of the presence and dynamic change of ctDNA to predict the tumor response and prognosis in patients with breast cancer treated with NAC. MATERIALS AND METHODS: Fifty-two patients with early breast cancer who underwent NAC were prospectively enrolled. Serial plasma samples before, during, and after NAC and paired tumor biopsies were harvested and subjected to deep targeted sequencing using a large next-generation sequencing panel that covers 1,021 cancer-related genes. RESULTS: Positive baseline ctDNA was detected in 21 of 44 patients before NAC. Most patients with positive ctDNA had one or more mutations confirmed in paired primary tumor. The ctDNA level after 2 cycles of NAC was predictive of local tumor response after all cycles of NAC (area under the curve, 0.81; 95% CI, 0.61 to 1.00). ctDNA tracking during NAC outperformed imaging in predicting the overall response to NAC. More importantly, positive baseline ctDNA is significantly associated with worse disease-free survival (P = .011) and overall survival (P = .004) in patients with early breast cancer, especially in estrogen receptor-negative patients. CONCLUSION: Our study demonstrated that ctDNA can be used to predict tumor response to NAC and prognosis in early breast cancer, providing information to tailor an individual's therapeutic regimen.

Bone marrow-derived mesenchymal stem cell-secreted IL-8 promotes the angiogenesis and growth of colorectal cancer.

Mesenchymal stem cells (MSCs) have recently been shown to home to tumors and contribute to the formation of the tumor-associated stroma. In addition, MSCs can secrete paracrine factors to facilitate tumor progression. However, the involvement of MSC-derived cytokines in colorectal cancer (CRC) angiogenesis and growth has not been clearly addressed. In this study, we report that interleukin-8 (IL-8) was the most highly upregulated pro-angiogenic factor in MSCs co-cultured with CRC cells and was expressed at substantially higher levels in MSCs than CRC cells. To evaluate the effect of MSC-derived IL-8 on CRC angiogenesis and growth, we used MSCs that expressed small hairpin (interfering) RNAs (shRNA) targeting IL-8 (shIL-8-MSCs). We found that MSC-secreted IL-8 promoted human umbilical vein endothelial cell (HUVEC) proliferation and migration, tube-formation ability and CRC cell proliferation. Additionally, in vivo studies showed that MSCs promoted tumor angiogenesis partially through IL-8. Taken together, these findings suggest that IL-8 secreted by MSCs promotes CRC angiogenesis and growth and can therefore serve as a potential novel therapeutic target.