Interferon-γ/IRF-1 pathway regulatory mechanisms of PD-L1 expression and relevance for immune checkpoint blockade in hepatocellular carcinoma (HCC)

Roles of Interferon Regulatory Factor 1 in Tumor Progression and Regression: Two Sides of a Coin

IRF1 is a transcription factor well known for its role in IFN signaling. Although IRF1 was initially identified for its involvement in inflammatory processes, there is now evidence that it provides a function in carcinogenesis as well. IRF1 has been shown to affect several important antitumor mechanisms, such as induction of apoptosis, cell cycle arrest, remodeling of tumor immune microenvironment, suppression of telomerase activity, suppression of angiogenesis and others. Nevertheless, the opposite effects of IRF1 on tumor growth have also been demonstrated. In particular, the "immune checkpoint" molecule PD-L1, which is responsible for tumor immune evasion, has IRF1 as a major transcriptional regulator. These and several other properties of IRF1, including its proposed association with response and resistance to immunotherapy and several chemotherapeutic drugs, make it a promising object for further research. Numerous mechanisms of IRF1 regulation in cancer have been identified, including genetic, epigenetic, transcriptional, post-transcriptional, and post-translational mechanisms, although their significance for tumor progression remains to be explored. This review will focus on the established tumor-suppressive and tumor-promoting functions of IRF1, as well as the molecular mechanisms of IRF1 regulation identified in various cancers.

Targeting ALK averts ribonuclease 1-induced immunosuppression and enhances antitumor immunity in hepatocellular carcinoma

Tumor-secreted factors contribute to the development of a microenvironment that facilitates the escape of cancer cells from immunotherapy. In this study, we conduct a retrospective comparison of the proteins secreted by hepatocellular carcinoma (HCC) cells in responders and non-responders among a cohort of ten patients who received Nivolumab (anti-PD-1 antibody). Our findings indicate that non-responders have a high abundance of secreted RNase1, which is associated with a poor prognosis in various cancer types. Furthermore, mice implanted with HCC cells that overexpress RNase1 exhibit immunosuppressive tumor microenvironments and diminished response to anti-PD-1 therapy. RNase1 induces the polarization of macrophages towards a tumor growth-promoting phenotype through activation of the anaplastic lymphoma kinase (ALK) signaling pathway. Targeting the RNase1/ALK axis reprograms the macrophage polarization, with increased CD8+ T- and Th1- cell recruitment. Moreover, simultaneous targeting of the checkpoint protein PD-1 unleashes cytotoxic CD8+ T-cell responses. Treatment utilizing both an ALK inhibitor and an anti-PD-1 antibody exhibits enhanced tumor regression and facilitates long-term immunity. Our study elucidates the role of RNase1 in mediating tumor resistance to immunotherapy and reveals an RNase1-mediated immunosuppressive tumor microenvironment, highlighting the potential of targeting RNase1 as a promising strategy for cancer immunotherapy in HCC.

Expression of programmed death-ligand 1, IRF1 and CD8 T lymphocyte infiltration in a primary subset of breast cancer patients in Sudan

Objectives

This study aimed to investigate the protein expression of programmed death ligand 1 (PD-L1) in breast cancer (BC) tissues and link this data with estrogen status, the expression of interferon regulatory factor1 (IRF-1), and CD8+T lymphocyte infiltration by immunohistochemistry (IHC). We also attempted to identify the association between PD-L1 expression, the cell proliferation index marker (Ki67), and lymph node involvement.

Methods

One hundred and fifty formalin-fixed and paraffin-embedded (FFPE) blocks of breast tissue were acquired from Sudanese females via The National Public Health Laboratory. FFPE blocks were subjected to antigen/antibody detection by IHC with antibodies raised against PD-L1, IRF1, and CD8. These data were analyzed alongside data extracted from medical records relating to estrogen receptor (ER) status, Ki67 index, and lymph node (LN) status.

Results

IHC analysis revealed a significant association between PD-L1 and CD8 (p = 0.010). In addition, regression analysis indicated the ability of IRF1 to induce PD-L1 expression levels in IRF1-positive cases that were two-fold higher than IRF1-deficient cases (odds ratio [OR]: 2.441 p = 0.035). Analysis also suggested that PD-L1 exerts impact on cell proliferation, as reflected by the Ki67 index. An independent t test showed that higher Ki67 scores were more frequent among PD-L1-positive patients than in PD-L1-negative patients (t = 2.608 p = 0.014). There was an inverse association between PD-L1 and ER status; ER-positive tumors exhibited negative PD-L1 expression and vice versa (p = 0.04). Furthermore, we investigated the prognostic value of PD-L1 by evaluating the association between PD-L1 and LNs dispersed variably with tumor cells; there was no statistically significant relationship between these factors (p > 0.05).

Conclusion

The expression of PD-L1 and IRF-1, along with the infiltration of CD8, represents a potent panel of biomarkers with which to identify BC patients with the highest probabilities of achieving an excellent response to immune therapy, particularly when taking ER status into account, as ER expression levels are known to be high when immune checkpoint blockers (ICBs) generate a poor response.

A Single Nucleotide Mixture Enhances the Antitumor Activity of Molecular-Targeted Drugs Against Hepatocellular Carcinoma

New strategies for molecular-targeted drug therapy for advanced hepatocellular carcinoma (HCC) ignore the contribution of the nutritional status of patients and nutritional support to improve physical status and immunity. We aimed to elucidate the role of a single nucleotide mixture (SNM) in the anti-tumor therapy of HCC, and to explore the importance of a SNM as adjuvant therapy for HCC. Compared with a lipid emulsion (commonly used nutritional supplement for HCC patients), the SNM could not induce metabolic abnormalities in HCC cells (Warburg effect), and did not affect expression of metabolic abnormality-related factors in HCC cells. The SNM could also attenuate the lymphocyte injury induced by antitumor drugs in vitro and in vivo, and promote the recruitment and survival of lymphocytes in HCC tissues. Using HCC models in SCID (server combined immune-deficiency) mice or BalB/c mice, the SNM had anti-tumor activity, and could significantly upregulate the antitumor activity of molecular-targeted drugs (tyrosine-kinase inhibitors [TKI] and immune-checkpoint inhibitors [ICI]) against HCC. We employed research models in vivo and in vitro to reveal the anti-tumor activity of the SNM on HCC. Our findings expand understanding of the SNM and contribute to HCC (especially nutritional support) therapy.