The efficacy of the cyclin-dependent kinase 4/6 inhibitor in endometrial cancer

Contemporary Use of Hormonal Therapy in Endometrial Cancer: a Literature Review

OPINION STATEMENT

Most endometrial cancers are estrogen receptor and progesterone receptor positive. Hormonal therapy in endometrial cancer is best used in patients with low-grade disease and hormone receptor positivity. Though not standard of care, hormonal treatment can be considered in endometrial cancer treatment in both the early-stage upfront setting for patients who are not surgical candidates and in advanced and recurrent endometrial cancer. In patients who desire fertility preservation or who are not surgical candidates, levonorgestrel intrauterine device and oral progesterone are preferred treatment options. In patients with advanced and metastatic disease, there is no standard-of-care second-line treatment, and hormonal treatment is a widely accepted option for low-grade disease. Beyond progesterone, selective estrogen receptor modulators, aromatase inhibitors, gonadotropin-releasing hormone agonists, and fulvestrant are hormonal treatment options. New therapies, such as MTOR inhibitors and CDK 4/6 inhibitors, have been extensively studied in breast cancer and are shown to be useful in conjunction with hormonal therapies particularly when there is suspected resistance to anti-estrogen treatment. Hormonal therapies also tend to be better tolerated than chemotherapy agents, making them a desirable option particularly in patients with lower performance status. Results from ongoing clinical trials will hopefully help shed light on the use of combination treatment in patients with hormone receptor-positive, low-grade metastatic, and recurrent endometrial cancer.

Pharmacological Treatment of Advanced, Persistent or Metastatic Endometrial Cancer: State of the Art and Perspectives of Clinical Research for the Special Issue "Diagnosis and Management of Endometrial Cancer"

Patients with metastatic or recurrent endometrial cancer (EC) not suitable for surgery and/or radiotherapy are candidates for pharmacological treatment frequently with unsatisfactory clinical outcomes. The purpose of this paper was to review the results obtained with chemotherapy, hormonal therapy, biological agents and immune checkpoint inhibitors in this clinical setting. The combination of carboplatin (CBDCA) + paclitaxel (PTX) is the standard first-line chemotherapy capable of achieving objective response rates (ORRs) of 43-62%, a median progression-free survival (PFS) of 5.3-15 months and a median overall survival (OS) of 13.2-37.0 months, respectively, whereas hormonal therapy is sometimes used in selected patients with slow-growing steroid receptor-positive EC. The combination of endocrine therapy with m-TOR inhibitors or cyclin-dependent kinase 4/6 inhibitors is currently under evaluation. Disappointing ORRs have been associated with epidermal growth factor receptor (EGFR) inhibitors, HER-2 inhibitors and multi-tyrosine kinase inhibitors used as single agents, and clinical trials evaluating the addition of bevacizumab to CBDCA + PTX have reported conflicting results. Immune checkpoint inhibitors, and especially pembrolizumab and dostarlimab, have achieved an objective response in 27-47% of highly pretreated patients with microsatellite instability-high (MSI-H)/mismatch repair (MMR)-deficient (-d) EC. In a recent study, the combination of lenvatinib + pembrolizumab produced a 24-week response rate of 38% in patients with highly pretreated EC, ranging from 64% in patients with MSI-H/MMR-d to 36% in those with microsatellite stable/MMR-proficient tumors. Four trials are currently investigating the addition of immune checkpoint inhibitors to PTX + CBDCA in primary advanced or recurrent EC, and two trials are comparing pembrolizumab + lenvatinib versus either CBDCA + PTX as a first-line treatment of advanced or recurrent EC or versus single-agent chemotherapy in advanced, recurrent or metastatic EC after one prior platinum-based chemotherapy.

Antitumorigenic effect of combination treatment with ONC201 and TRAIL in endometrial cancer in vitro and in vivo

ONC201 demonstrated promising activity in patients with advanced endometrial cancer in a Phase I clinical trial. ONC201 activates the integrated stress response (ISR) and upregulates TRAIL and its receptor DR5. We hypothesized ONC201 upregulation of DR5 could sensitize tumors to TRAIL and combination of ONC201 and TRAIL would lead to enhanced cell death in endometrial cancer models. Five endometrial cancer cell lines AN3CA, HEC1A, Ishikawa, RL952, and KLE as well as a murine xenograft model were treated with ONC201 alone or in combination with TRAIL. ONC201 decreased the cell viability of all five endometrial cancer cell lines at clinically achievable low micro-molar concentrations (2–4 μM). ONC201 activated the ISR and induced protein expression of TRAIL and DR5 at the cell surface. Pretreatment with ONC201 sensitized endometrial cancer cell lines to TRAIL, leading to increased cell death induction compared to either agent alone. Tumor growth was reduced in vivo by the ONC201/TRAIL combination treatment in the xenograft model of endometrial cancer (p = .014). Mice treated with combination treatment survived significantly longer than mice from the three control groups (p = .018). ONC201 decreased cell viability in endometrial cancer cells lines primarily through growth arrest while the combination of ONC201 and TRAIL promoted cell death in vitro and in vivo. Our results suggest a novel cancer therapeutic strategy that can be further investigated in the clinic.

Opportunities for Antigen Discovery in Metastatic Breast Cancer

Immune checkpoint inhibitor-based immunotherapy (ICI) of breast cancer is currently efficacious in a fraction of triple negative breast cancers (TNBC) as these cancers generally carry high tumor mutation burden (TMB) and show increased tumor infiltration by CD8⁺ T cells. However, most estrogen receptor positive breast cancers (ERBC) have low TMB and/or are infiltrated with immunosuppressive regulatory T cells (Tregs) and thus fail to induce a significant anti-tumor immune response. Our understanding of the immune underpinning of the anti-tumor effects of CDK4/6 inhibitor (CDKi) treatment coupled with new knowledge about the mechanisms of tolerance to self-antigens suggests a way forward, specifically via characterizing and exploiting the repertoire of tumor antigens expressed by metastatic ERBC. These treatment-associated tumor antigens (TATA) may include the conventional tumor neoantigens (TNA) encoded by single nucleotide mutations, TNA encoded by tumor specific aberrant RNA transcription, splicing and DNA replication induced frameshift (FS) events as well as the shared tumor antigens. The latter may include the conventional tumor associated antigens (TAA), cancer-testis antigens (CTA) and antigens encoded by the endogenous retroviral (ERV) like sequences and repetitive DNA sequences induced by ET and CDKi treatment. An approach to identifying these antigens is outlined as this will support the development of a multi-antigen-based immunotherapy strategy for improved targeting of metastatic disease with potential for minimal autoimmune toxicity against normal tissues.

Endometrial Cancer: When Upfront Surgery Is Not an Option

Background and Summary: The management of endometrial cancer, in an ever-older population with considerable comorbidity, remains a challenge for gynecological and radiation oncologists. Key Message: The present paper reviews literature data on treatment options for endometrial cancer patients unfit for surgery.

Palbociclib Promotes Dephosphorylation of NPM/B23 at Threonine 199 and Inhibits Endometrial Cancer Cell Growth

Endometrial cancer incidence rates are growing, especially in countries with rapid socioeconomic transitions. Despite recent advances in chemotherapy, hormone therapy, and targeted therapy, advanced/recurrent disease remains a clinical challenge. Palbociclib—a selective inhibitor of cyclin-dependent kinases (CDK) 4/6—has therapeutic potential against estrogen receptor (ER)-positive and HER2-negative breast cancer. However, the question as to whether it can be clinically useful in endometrial cancer remains open. Here, we show that combined treatment with palbociclib and megesterol acetate exerts synergistic antiproliferative effects against endometrial cancer cells. Treatment of cancer cells with palbociclib suppressed NPM/B23 phosphorylation at threonine 199 (Thr199). We further demonstrated that CDK6 acts as a NPM/B23 kinase. Palbociclib-induced NPM/B23 dephosphorylation sensitized endometrial cancer cells to megesterol acetate through the upregulation of ERα expression. Immunohistochemistry revealed an overexpression of phospho-NPM/B23 (Thr199) in human endometrial cancer, and phospho-NPM/B23 (Thr199) expression levels were inversely associated with Erα in clinical specimen. In a xenograft tumor model, the combination of palbociclib and megesterol acetate successfully inhibited tumor growth. Taken together, our data indicate that palbociclib promoted NPM/B23 dephosphorylation at Thr199—an effect mediated by disruption of CDK6 kinase activity. We conclude that palbociclib holds promise for the treatment of endometrial cancer when used in combination with megesterol acetate.

Role of Cyclin-Dependent Kinase Inhibitors in Endometrial Cancer

Endometrial Cancer (EC) is an important cause of death in women worldwide. Despite early diagnosis and optimal treatment of localized disease, relapsed patients have few therapeutic options because after first line therapy, currently no standard of care exists. On the basis of endocrine positivity of most endometrioid ECs, Endocrine Therapy (ET) is a reasonable and widely accepted option. Better knowledge of molecular mechanisms involved in cancer highlighted the deregulated activity of Cyclin-Dependent Kinases (CDKs) in the cell cycle as a hallmark of carcinogenesis supporting the development of a new class of drugs: CDK inhibitors (CDKis). The aim of this review is to give an overview on CDKis preclinical, early clinical activity and future development in EC. Use of CDKis has a strong preclinical rationale but we have poor clinical data. Similar to breast cancer, most ongoing trials are investigating synergistic associations between CDKis and ET. These trials will probably help in defining the best clinical setting of CDKis in ECs, which are the best partner drugs, and how to manage CDKis toxicities with a focus on potential biomarkers of response.

The efficacy of HRAS and CDK4/6 inhibitors in anaplastic thyroid cancer cell lines

PURPOSE

Anaplastic thyroid carcinomas (ATCs) are non-responsive to multimodal therapy, representing one of the major challenges in thyroid cancer. Previously, our group has shown that genes involved in cell cycle are deregulated in ATCs, and the most common mutations in these tumours occurred in cell proliferation and cell cycle related genes, namely TP53, RAS, CDKN2A and CDKN2B, making these genes potential targets for ATCs treatment. Here, we investigated the inhibition of HRAS by tipifarnib (TIP) and cyclin D-cyclin-dependent kinase 4/6 (CDK4/6) by palbociclib (PD), in ATC cells.

METHODS

ATC cell lines, mutated or wild type for HRAS, CDKN2A and CDKN2B genes, were used and the cytotoxic effects of PD and TIP in each cell line were evaluated. Half maximal inhibitory concentration (IC50) values were determined for these drugs and its effects on cell cycle, cell death and cell proliferation were subsequently analysed.

RESULTS

Cell culture studies demonstrated that 0.1 µM TIP induced cell cycle arrest in the G2/M phase (50%, p < 0.01), cell death, and inhibition of cell viability (p < 0.001), only in the HRAS mutated cell line. PD lowest concentration (0.1 µM) increased significantly cell cycle arrest in the G0/G1 phase (80%, p < 0.05), but only in ATC cell lines with alterations in CDKN2A/CDKN2B genes; additionally, 0.5 µM PD induced cell death. The inhibition of cell viability by PD was more pronounced in cells with alterations in CDKN2A/CDKN2B genes (p < 0.05) and/or cyclin D1 overexpression.

CONCLUSIONS

This study suggests that TIP and PD, which are currently in clinical trials for other types of cancer, may play a relevant role in ATC treatment, depending on the specific tumour molecular profile.

Phase II trial of palbociclib in patients with metastatic urothelial cancer after failure of first-line chemotherapy

Background

The majority of urothelial cancers (UC) harbor alterations in retinoblastoma (Rb) pathway genes that can lead to loss of Rb tumour suppressor function. Palbociclib is an oral, selective inhibitor of CDK 4/6 that restores Rb function and promotes cell cycle arrest.

Methods

In this phase II trial, patients with metastatic platinum-refractory UC molecularly selected for p16 loss and intact Rb by tumour immunohistochemistry received palbociclib 125 mg p.o. daily for 21 days of a 28-day cycle. Primary endpoint was progression-free survival at 4 months (PFS4) using a Simon’s two-stage design. Next-generation sequencing including Rb pathway alterations was conducted.

Results

Twelve patients were enrolled and two patients (17%) achieved PFS4 with insufficient activity to advance to stage 2. No responses were seen. Median PFS was 1.9 months (95% CI 1.8–3.7 months) and median overall survival was 6.3 months (95% CI 2.2–12.6 months). Fifty-eight percent of patients had grade ≥3 hematologic toxicity. There were no CDKN2A alterations found and no correlation of Rb pathway alterations with clinical outcome.

Conclusions

Palbociclib did not demonstrate meaningful activity in selected patients with platinum-refractory metastatic UC. Further development of palbociclib should only be considered with improved integral biomarker selection or in rational combination with other therapies.

Oncogenic c-terminal cyclin D1 (CCND1) mutations are enriched in endometrioid endometrial adenocarcinomas

Cyclin D1 (CCND1) is a core cell cycle regulator and is frequently overexpressed in human cancers, often via amplification, translocation or post-transcription regulation. Accumulating evidence suggests that mutations of the CCND1 gene that result in nuclear retention and constitutive activation of CDK4/6 kinases are oncogenic drivers in cancer. However, the spectrum of CCND1 mutations across human cancers has not been systematically investigated. Here, we retrospectively mined whole-exome sequencing data from 124 published studies representing up to 29,432 cases from diverse cancer types and sites of origin, including carcinoma, melanoma, sarcoma and lymphoma/leukemia, via online tools to determine the frequency and spectrum of CCND1 mutations in human cancers and their associated clinico-pathological characteristics. Overall, in contrast to gene amplification, which occurred at a frequency of 4.8% (1,419 of 28,769 cases), CCND1 mutations were of very low frequency (0.5%, 151 of 29,432 cases) across all cancers, but were predominantly enriched in uterine endometrioid-type adenocarcinoma (6.5%, 30 of 458 cases) in both primary tumors and in advanced, metastatic endometrial cancer samples. CCND1 mutations in endometrial endometrioid adenocarcinoma occurred most commonly in the c-terminus of cyclin D1, as putative driver mutations, in a region thought to result in oncogenic activation of cyclin D1 via inhibition of Thr-286 phosphorylation and nuclear export, thereby resulting in nuclear retention and protein overexpression. Our findings implicate oncogenic c-terminal mutations of CCND1 in the pathogenesis of a subset of human cancers and provide a key resource to guide future preclinical and clinical investigations.

Palbociclib-The First of a New Class of Cell Cycle Inhibitors

During the last decades, much has been learned about with cyclin-dependent kinases (CDK) playing a pivotal role in the cell cycle regulation. CDK4/6 is the key regulator of the G1-S transition. Palbociclib (PD 0332991, Ibrance®) is the first oral CDK4/6 inhibitor showing a substantially improved median progression-free survival (PFS) in advanced estrogen receptor (ER) positive and human epidermal growth factor receptor 2 (HER2) negative breast cancer. This PFS prolongation was seen both with letrozole as first-line therapy (24.8 vs. 14.5 months [PALOMA 2]) and with fulvestrant in endocrine pretreated patients (9.2 vs. 3.8 months [PALOMA-3]). The main toxicity is neutropenia due to cell cycle arrest which can be easily managed with dose interruption or dose reduction leading to a favorable safety profile with delayed deterioration of global quality of life (QoL). Palbociclib is approved by the Federal Drug Administration (FDA) and the European Medicines Agency (EMA) for ER-positive/HER2-negative advanced breast cancer. Despite the well-understood mode of action of palbociclib, predictive biomarkers are not yet defined. In conclusion, inhibition of CDK4/6 using palbociclib in combination with endocrine therapy is an efficient and well-tolerated treatment option in ER-positive/HER2-negative advanced breast cancer. Ongoing clinical trials are investigating the role of palbociclib in early breast cancer as well as in other types of cancer.