The development and progression of most cancers have been well recognized as the result of highly activated cell cycle. Cyclin dependent kinase 4/6 plays important roles not only in mitosis, but also in multiple biological processes that contribute to cancer development, such as aging, apoptosis and histone modification. Three FDA approved CDK4/6 inhibitors, Palbociclib, Ribociclib and Abemaciclib, have been used as targeted cancer therapeutic agents to benefit patients with endocrine therapy-resistant breast cancer and other types of cancer, prolonging their survival. However, the clinical application of these inhibitors also leads to acquired drug resistance and other problems. This paper reviews the regulatory roles of CDK4/6, the application of CDK4/6 inhibitors in cancer and the challenge of drug resistance.
Breast Neoplasms ; Cyclin-Dependent Kinase 4/therapeutic use* ; Cyclin-Dependent Kinase 6/therapeutic use* ; Female ; Humans ; Molecular Targeted Therapy ; Protein Kinase Inhibitors/therapeutic use* ; Signal Transduction

The introduction of cyclin-dependent kinase (CDK) 4/6 inhibitors has revolutionized the clinical management paradigm of hormone receptor (HR) positive/human epidermal growth factor receptor (HER) 2 negative breast cancer. As of today, CDK 4/6 inhibitors including Palbociclib, Ribociclib, and Abemaciclib have been widely approved by regulatory agencies. Randomized clinical trials demonstrated that CDK 4/6 inhibitors in combination with an aromatase inhibitor (AI) or fulvestrant in the first-, second- or later-line setting for HR positive/HER2 negative locally advanced or metastatic breast cancer led to substantial reduction in the risk of disease progression or death. Adverse effects of treatment were manageable and as or better than expected in terms of patient satisfaction. Considering CDK4/6 inhibitors in combination with endocrine therapy being a novel approach in China clinical practice, the panel developed the consensus comprehensively describing the pharmacology properties, monitoring strategy during treatment and adverse events management, to facilitate greater understanding in Chinese oncologists of a whole new therapeutic class of drug, promote accuracy of clinical decision and help reach the ultimate goal of improving survival and quality of life of the target patient population.
Antineoplastic Combined Chemotherapy Protocols/therapeutic use* ; Breast Neoplasms/drug therapy* ; China ; Consensus ; Cyclin-Dependent Kinase 4 ; Cyclin-Dependent Kinase 6 ; Humans ; Protein Kinase Inhibitors/therapeutic use* ; Quality of Life ; Receptor, ErbB-2

OBJECTIVETo explore anti-cancer effect and mechanism of green tea extract (GTE) in three human oral squamous carcinoma cell lines (CAL-27, SCC-25 and KB).

METHODSThe cell lines were in vitro cultured and its growth inhibition was detected by MTT. After screening most sensitive cell line, effect of GTE on CAL-27 cell cycle was analyzed by flow cytometry. The protein expression of GTE on CAL-27 cell strain was determined by protein chip technique. The protein expression of CDK4, CDK6, and p-PDK1 was verified by using Western blot.

RESULTSCompared with the control group, the inhibition rate on CAL-27 increased significantly after treated by 50, 100, 200, and 400 μg/mL GTE; the inhibition rate on KB increased after treated by 100, 200, and 400 μg/mL GTE; the inhibition rate on SCC-25 increased after treated by 25, 50, 100, 200, and 400 μg/mL GTE, all with statistical difference and in dose dependant manner (P < 0.01). Flow cytometric analysis showed that, when compared with the control group, 50 μg/mL GTE arrested CAL-27 cells in the G2/M phase (P < 0.05), and 100 μg/mL GTE arrested CAL-27 cells in the G2/M phase with concurrent decreased cells in the G0/G1 phase (P < 0.01). Totally 107 proteins were analyzed by protein chip technique. After treated by GTE, a total of 13 proteins significantly changed in CAL-27 cell line. Western blot showed that 25, 50, and 100 μg/mL GTE inhibited the expression of phopho-phosphoinositide-dependent protein kinase 1 (p-PDK1), cyclin-dependent kinase 4 (CDK4), and CDK6 of CAL-27 cell line with statistical difference (P < 0.05). The higher the drug concentration, the higher the inhibition rate (P < 0.05).

CONCLUSIONSGTE could inhibit the proliferation of different human oral squamous carcinoma cell lines. CAL-27 is a sensitive cell line. GTE significantly affected EGFR and Notch signal network, and influenced changes of cell cycle related protein expression levels through the aforesaid channels, resulting in cell cycle arrest in S and G2/M phases.

Antineoplastic Agents, Phytogenic ; pharmacology ; therapeutic use ; Antioxidants ; Carcinoma, Squamous Cell ; Cell Cycle ; Cell Line, Tumor ; Cyclin-Dependent Kinase 4 ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; G1 Phase ; Humans ; Mouth Neoplasms ; Tea

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have led transformative breakthrough of clinical therapy for hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER-2)-negative breast cancer patients. CDK4/6 inhibitors that have been marketed in China include Ribociclib, Palbociclib, Abemaciclib and Dalpiciclib. For HR-positive HER-2-negative locally advanced and metastatic breast cancer, CDK4/6 inhibitors combined with endocrine therapy have become standard regimen, which can prolong the survival of patients. In the adjuvant treatment stage of early breast cancer, CDK4/6 inhibitors have also achieved positive results and been approved for indications. At present, CDK4/6 inhibitors have been widely used in clinical practice in China. In order to further improve the standardized application of CDK4/6 inhibitors in China, the Breast Cancer Expert Committee of the National Center for Cancer Quality Control and the Professional Committee of Clinical Research of Cancer Drugs of the Chinese Anti-Cancer Association organized the related expert to update the consensus based on the "CDK4/6 inhibitor consensus on clinical application of in the treatment of hormone receptor positive human epidermal growth factor receptor 2 negative advanced breast cancer (2021 edition)" . The updated consensus systematically introduces the pharmacological characteristics, drug monitoring and adverse event management, etc., of CDK4/6 inhibitors to promote the accuracy of clinical decision-making with the ultimate goal to prolong the overall survival of patients and improve the quality of life.
Humans ; Female ; Breast Neoplasms/pathology* ; Quality of Life ; Consensus ; Triple Negative Breast Neoplasms/drug therapy* ; Receptor, ErbB-2/metabolism* ; Protein Kinase Inhibitors ; Antineoplastic Combined Chemotherapy Protocols/therapeutic use* ; Cyclin-Dependent Kinase 4/metabolism*