AR-A014418 regulates intronic polyadenylation and transcription of PD-L1 through inhibiting CDK12 and CDK13 in tumor cells

BACKGROUND

Immune checkpoint molecules, especially programmed death 1 (PD-1) and its ligand, programmed death ligand 1 (PD-L1), protect tumor cells from T cell-mediated killing. Immune checkpoint inhibitors, designed to restore the antitumor immunosurveillance, have exhibited significant clinical benefits for patients with certain cancer types. Nevertheless, the relatively low response rate and acquisition of resistance greatly limit their clinical applications. A deeper understanding of the regulatory mechanisms of PD-L1 protein expression and activity will help to develop more effective therapeutic strategies.

METHODS

The effects of AR-A014418 and THZ531 on PD-L1 expression were detected by western blot, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and flow cytometry. In vitro kinase assays with recombinant proteins were performed to confirm that AR-A014418 functioned as a CDK12 and CDK13 dual inhibitor. The roles of CDK12 and CDK13 in intronic polyadenylation (IPA) and transcription of PD-L1 were determined via RNA interference or protein overexpression. T-cell cytotoxicity assays were used to validate the activation of antitumor immunity by AR-A014418 and THZ531.

RESULTS

AR-A014418 inhibits CDK12 to enhance the IPA, and inhibits CDK13 to repress the transcription of PD-L1. IPA generates a secreted PD-L1 isoform (PD-L1-v4). The extent of IPA was not enough to reduce full-length PD-L1 expression obviously. Only the superposition of enhancing IPA and repressing transcription (dual inhibition of CDK12 and CDK13) dramatically suppresses full-length PD-L1 induction by interferon-γ. AR-A014418 and THZ531 could potentiate T-cell cytotoxicity against tumor cells.

CONCLUSIONS

Our work identifies a new regulatory pathway for PD-L1 expression and discovers CDK12 and CDK13 as promising drug targets for immune modulation and combined therapeutic strategies.

Ipilimumab plus nivolumab in avelumab-refractory Merkel cell carcinoma: a multicenter study of the prospective skin cancer registry ADOREG

Merkel cell carcinoma is a rare, highly aggressive skin cancer with neuroendocrine differentiation. Immune checkpoint inhibition has significantly improved treatment outcomes in metastatic disease with response rates to programmed cell death protein 1/programmed cell death 1 ligand 1 (PD-1/PD-L1) inhibition of up to 62%. However, primary and secondary resistance to PD-1/PD-L1 inhibition remains a so far unsolved clinical challenge since effective and safe treatment options for these patients are lacking.Fourteen patients with advanced (non-resectable stage III or stage IV, Union international contre le cancer 2017) Merkel cell carcinoma with primary resistance to the PD-L1 inhibitor avelumab receiving subsequent therapy (second or later line) with ipilimumab plus nivolumab (IPI/NIVO) were identified in the prospective multicenter skin cancer registry ADOREG. Five of these 14 patients were reported previously and were included in this analysis with additional follow-up. Overall response rate, progression-free survival (PFS), overall survival (OS) and adverse events were analyzed.All 14 patients received avelumab as first-line treatment. Thereof, 12 patients had shown primary resistance with progressive disease in the first tumor assessment, while two patients had initially experienced a short-lived stabilization (stable disease). Six patients had at least one systemic treatment in between avelumab and IPI/NIVO. In total, 7 patients responded to IPI/NIVO (overall response rate 50%), and response was ongoing in 4 responders at last follow-up. After a median follow-up of 18.85 months, median PFS was 5.07 months (95% CI 2.43-not available (NA)), and median OS was not reached. PFS rates at 12 months and 24 months were 42.9% and 26.8 %, respectively. The OS rate at 36 months was 64.3%. Only 3 (21%) patients did not receive all 4 cycles of IPI/NIVO due to immune-related adverse events.In this multicenter evaluation, we observed high response rates, a durable benefit and promising OS rates after treatment with later-line combined IPI/NIVO. In conclusion, our patient cohort supports our prior findings with an encouraging activity of second-line or later-line IPI/NIVO in patients with anti-PD-L1-refractory Merkel cell carcinoma.

Human Rhinovirus Infection Enhances the Th2 Environment in Allergic and Non-allergic Patients with Chronic Rhinosinusitis

Objectives.

This study was conducted to determine whether patients with allergic rhinitis might be more susceptible to human rhinovirus (HRV) infection and whether the effects of infection on the elicited immune responses are different in allergic and non-allergic patients with chronic rhinosinusitis (CRS).

Methods.

Uncinate process tissues were obtained from 61 CRS patients (of whom 39 had allergies and 22 did not) and were infected with HRV-16 using an air-liquid interface organ culture system. The expression levels of programmed cell death-ligand (PD-L)1, PD-L2, intracellular adhesion molecule 1, interferon-gamma (IFN-γ), interleukin (IL)-4, IL-5, and IL-10 were evaluated in the infected nasal mucosa.

Results.

The HRV infection rates were not significantly different between the allergy (74.4%) and non-allergy (72.7%) groups. In the allergy group, the expression of PD-L1 (P=0.013) and IL-10 (P=0.040) was significantly elevated in the HRV-infected tissues, and there was a strong correlation between PD-L1 and IL-10 (r=0.868, P<0.001). In contrast, infected tissues from the non-allergy group displayed increased levels of IL-4 (P=0.039), IL-5 (P=0.023), and IFN-γ (P=0.031), as well as an increased IL-4/IFN-γ ratio, after HRV infection (P=0.043).

Conclusion.

This study showed that HRV infection rates were similar in the nasal mucosa of patients with CRS regardless of the presence of allergic rhinitis. HRV infection enhanced the Th2 environment by modulating PD-L1 and PD-L2 expression levels in allergic mucosa and by increasing the IL-4/IFN-γ ratio in non-allergic mucosa.

Significance of PD-L1 expression in carbon-ion radiotherapy for uterine cervical adeno/adenosquamous carcinoma

OBJECTIVE

Programmed cell death-ligand 1 (PD-L1) is expressed in tumor cells and has been shown to predict clinical outcomes of several types of malignancies. The aim of this study was to investigate the effects of carbon-ion (C-ion) beam irradiation on PD-L1 expression in human uterine cervical adeno/adenosquamous carcinoma (UCAA) cells and clinical samples and to identify the prognostic factors for outcomes after C-ion radiotherapy (CIRT).

METHODS

The effects of C-ion irradiation on PD-L1 expression in human UCAA and cervical squamous cell carcinoma cells were examined by flow cytometry. We examined PD-L1 expression in UCAA biopsy specimens from 33 patients before CIRT started (pre-CIRT) and after 12 Gy (relative biological effectiveness [RBE]) irradiation (post-12Gy-C) in 4 fractions of CIRT to investigate the correlation between PD-L1 status and clinical outcomes.

RESULTS

The PD-L1 expression was upregulated by C-ion beam in a dose-dependent manner in HeLa and SiHa cells through phosphorylated Chk1. The overall frequencies of pre-CIRT and post-12Gy-C PD-L1 positivity were 45% (15/33) and 67% (22/33), respectively. The post-12Gy-C PD-L1 expression was significantly elevated compared to the pre-CIRT PD-L1 expression. There was no significant relationship between the pre-CIRT PD-L1 status and clinical outcomes, such as local control (LC), progression-free survival (PFS), and overall survival (OS). However, the post-12Gy-C PD-L1 expression had better correlation with PFS, but not with LC and OS.

CONCLUSION

CIRT can induce PD-L1 expression in UCAA and we propose that PD-L1 expression after starting CIRT may become as a predictive prognostic marker in CIRT for UCAA.