Inhibitors of CDK family: New Perspective and Rationale for Drug Combination in Preclinical Model of Solid Tumors

The cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor palbociclib is an emerging cancer therapeutic that just recently gained Food and Drug Administration approval for treatment of estrogen receptor (ER)-positive, human epidermal growth factor receptor (Her)2-negative breast cancer in combination with the ER degrader fulvestrant. However, CDK4/6 inhibitors are not cancer-specific and may affect also other proliferating cells. Given the importance of T cells in antitumor defense, we studied the influence of palbociclib/fulvestrant on human CD3+ T cells and novel emerging T cell-based cancer immunotherapies. Palbociclib considerably inhibited the proliferation of activated T cells by mediating G0/G1 cell cycle arrest. However, after stopping the drug supply this suppression was fully reversible. In light of combination approaches, we further investigated the effect of palbociclib/fulvestrant on T cell-based immunotherapies by using a CD3-PSCA bispecific antibody or universal chimeric antigen receptor (UniCAR) T cells. Thereby, we observed that palbociclib clearly impaired T cell expansion. This effect resulted in a lower total concentration of interferon-γ and tumor necrosis factor, while palbociclib did not inhibit the average cytokine release per cell. In addition, the cytotoxic potential of the redirected T cells was unaffected by palbociclib and fulvestrant. Overall, these novel findings may have implications for the design of treatment modalities combining CDK4/6 inhibition and T cell-based cancer immunotherapeutic strategies.

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5 citations

CDK, Cyclins, CKI, and other key molecular players in CDK activity/inhibition. Clockwise, starting from G1 to S phase progression: CDKN2A is transcribed by alternative splicing either into p16 or p14, which respectively inhibit CDK4/6/Cyclin D complexes and MDM2 activity. MDM2, an ubiquitin ligase, ubiquitinates p53 targeting it to the proteasome; p53 has p21 as a direct transcriptional target, and p21 in turn inhibits CDK2/Cyclin E complexes. Cyclin E expression is regulated by E2F transcription factor, which in turn is released from Rb protein grip (usually blocking its transactivation domain) when CDK4/6/Cyclin D complexes phosphorylate Rb, facilitating G1 to S phase progression. The ubiquitin ligase Skp2 targets p21 and p27 for proteasomal degradation, thus promoting CDK2/Cyclin E, CDK2/Cyclin A activity in S phase progression, CDK1/Cyclin A activity for G2 to M transition, which is also fostered by releasing p21 inhibitory activity on CDK1/Cyclin B; DUX4 can also bind CDK1, thus preventing CDK1/Cyclin B interaction. MDM2 activity can also be inhibited with MDM2 inhibitors (MDM2i), while CDK inhibitors (CDKi) currently in use in clinical practice are mainly CDK4/6 inhibitors. MDM2i and CDKi are highlighted in bold (red) in Figure 1. Created with BioRender.com.

Review

19 January 2023

Targeting cyclin-dependent kinases in sarcoma treatment: Current perspectives and future directions

Alessandra Merlini

, 6 more and

Giovanni Grignani

3,887 views

1 citations

Original Research

08 August 2022

Adapalene inhibits the growth of triple-negative breast cancer cells by S-phase arrest and potentiates the antitumor efficacy of GDC-0941

Umar Mehraj

, 4 more and

Manzoor Ahmad Mir

Although advances in diagnostics and therapeutics have prolonged the survival of triple-negative breast cancer (TNBC) patients, metastasis, therapeutic resistance, and lack of targeted therapies remain the foremost hurdle in the effective management of TNBC. Thus, evaluation of new therapeutic agents and their efficacy in combination therapy is urgently needed. The third-generation retinoid adapalene (ADA) has potent antitumor activity, and using ADA in combination with existing therapeutic regimens may improve the effectiveness and minimize the toxicities and drug resistance. The current study aimed to assess the anticancer efficacy of adapalene as a combination regimen with the PI3K inhibitor (GDC-0941) in TNBC in vitro models. The Chou–Talalay’s method evaluated the pharmacodynamic interactions (synergism, antagonism, or additivity) of binary drug combinations. Flow cytometry, Western blotting, and in silico studies were used to analyze the mechanism of GDC–ADA synergistic interactions in TNBC cells. The combination of GDC and ADA demonstrated a synergistic effect in inhibiting proliferation, migration, and colony formation of tumor cells. Accumulation of reactive oxygen species upon co-treatment with GDC and ADA promoted apoptosis and enhanced sensitivity to GDC in TNBC cells. The findings indicate that ADA is a promising therapeutic agent in treating advanced BC tumors and enhance sensitivity to GDC in inhibiting tumor growth in TNBC models while reducing therapeutic resistance.

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26 citations

(A) Chest-wall Ewing sarcoma PDOX model. (B) Peritoneum and retroperitoneum soft-tissue sarcoma PDOX models. (C) Osteosarcoma PDOX model.

Review

08 August 2022

Review: Precise sarcoma patient-derived orthotopic xenograft (PDOX) mouse models enable identification of novel effective combination therapies with the cyclin-dependent kinase inhibitor palbociclib: A strategy for clinical application

Takashi Higuchi

, 7 more and

Robert M. Hoffman

3,283 views

12 citations

Cells were treated with 1 μM A and 0.5, 2, or 6.5 μM L for HUH7, SNU398, and HepG2, respectively, alone or in combination for 24 h. The cells were lysed and the expression of the indicated proteins was evaluated by Western blot analysis. Data are representative of two independent experiments.

Original Research

22 July 2022

CDK4/6 inhibitors improve the anti-tumor efficacy of lenvatinib in hepatocarcinoma cells

Graziana Digiacomo

, 12 more and

Pier Giorgio Petronini

3,833 views

16 citations

Original Research

13 July 2022

Stable CDK12 Knock-Out Ovarian Cancer Cells Do Not Show Increased Sensitivity to Cisplatin and PARP Inhibitor Treatment

Rosaria Chilà

, 8 more and

Giovanna Damia

4,318 views

5 citations

Original Research

25 May 2022

Tizoxanide Promotes Apoptosis in Glioblastoma by Inhibiting CDK1 Activity

Si Huang

, 6 more and

Shilin Luo

Cyclin-dependent kinases are potential targets of TIZ against glioma. (A) The structure of TIZ. (B) Venn diagram of the shared targets and the TIZ-target network. The related targets of GBM and TIZ were obtained from GeneCards and SEAware, respectively. (C) KEGG pathway enrichment analysis of the top 20 target genes. (D) Schematic diagram of target network connections and the top 10 targets and their scores. NetworkAnalyzer was employed to analyze the node’s degree and related parameters. The color of nodes changed from orange to red, which indicates that the affinity degree gradually increases from weak to strong. (E) KEGG pathway enrichment analysis of targets whose score was greater than 15. (F) Docking diagram of CDK1 and TIZ. Key interactions include hydrogen bonds formed by multiple atoms of TIZ with ASP86, Lys89, Glu81, and Leu83.

The antiparasitic drug nitazoxanide (NTZ) has received considerable attention for its potential in cancer therapy. In this study, we demonstrate that tizoxanide (TIZ), an active metabolite of NTZ, exhibits antiglioma activity in vitro and in vivo by inducing G2/M cell cycle arrest and apoptosis. In vitro, TIZ dose-dependently inhibited the proliferation of U87, U118, and A172 human glioblastoma (GBM) cells at 48 h with IC₅₀ values of 1.10, 2.31, and 0.73 µM, respectively. Treatment with TIZ (1 and 10 µM) also dose-dependently inhibited the colony formation of these GBM cells and accumulated ROS damage in the nucleus. In silico target fishing combined with network pharmacological disease spectrum analyses of GBM revealed that cycle-dependent kinase 1 (CDK1) is the most compatible target for TIZ and molecular docking by Molecule Operating Environment (MOE) software confirmed it. Mechanistically, TIZ inhibited the phosphorylation of CDK1 at Thr161 and decreased the activity of the CDK1/cyclin B1 complex, arresting the cell cycle at the G2/M phase. TIZ may induce apoptosis via the ROS-mediated apoptotic pathway. In vivo, TIZ suppressed the growth of established subcutaneous and intracranial orthotopic xenograft models of GBM without causing obvious side effects and prolonged the survival of nude mice bearing glioma. Taken together, our results demonstrated that TIZ might be a promising chemotherapy drug in the treatment of GBM.

2,907 views

12 citations

Western blot analysis showed higher CDK6 protein expression in T24 cell lines compared to 5637 cell lines (A). Relative growth inhibition curves of ribociclib (B) and palbociclib (C) in 5637 or T24 cell lines were from three independent experiments. Mean IC50 value of ribociclib was 21.12 ± 0.36 μM for the 5637 cells and 5.88 ± 0.86 μM for the T24 cells (p <0.001), and mean IC50 value of palbociclib was 28.44 ± 4.4 μM for the 5637 cells and 1.16± 0.89 μM for the T24 cells (p = 0.001).

Original Research

08 April 2022

CDK6 Immunophenotype Implicates Potential Therapeutic Application of CDK4/6 Inhibitors in Urothelial Carcinoma

Ran Sun

, 5 more and

Xueju Wang

2,060 views

2 citations

Original Research

22 February 2022

Adapalene Inhibits Prostate Cancer Cell Proliferation In Vitro and In Vivo by Inducing DNA Damage, S-phase Cell Cycle Arrest, and Apoptosis

Hai-bin Nong

, 7 more and

Shao-Hui Zong

Aims: Prostate cancer is a well-known aggressive malignant tumor in men with a high metastasis rate and poor prognosis. Adapalene (ADA) is a third-generation synthetic retinoid with anticancer properties. We investigated the anti-tumor activity and molecular mechanisms of ADA in the RM-1 prostate cancer cell line in vivo and in vitro.

Methods: The effects of ADA on cell proliferation were estimated using the CCK-8 and colony formation assays. The wound-healing assay and the Transwell assay were employed to examine the migratory capacity and invasiveness of the cells. Flow cytometry was utilized to evaluate the cell cycle and apoptosis, and Western blotting analysis was used to assess the expression of the associated proteins. Micro-CT, histomorphological, and immunohistochemical staining were used to assess the effects of ADA on bone tissue structure and tumor growth in a mouse model of prostate cancer bone metastasis.

Result: ADA dramatically inhibited cell proliferation, migration, invasiveness, and induced S-phase arrest and apoptosis. ADA also regulated the expression of S-phase associated proteins and elevated the levels of DNA damage markers, p53, and p21 after ADA treatment, suggesting that the anti-tumor effect of ADA manifests through the DNA damage/p53 pathway. Furthermore, we observed that ADA could effectively inhibited tumor growth and bone destruction in mice.

Conclusion: ADA inhibited prostate cancer cell proliferation, elicited apoptosis, and arrested the cell cycle in the S-phase. ADA also slowed the rate of tumor growth and bone destruction in vitro. Overall, our results suggest that ADA may be a potential treatment against prostate cancer.

3,471 views

12 citations

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