BCL6 promotes a stem-like CD8+ T cell program in cancer via antagonizing BLIMP1.

Overcoming CD8+ T cell exhaustion is critical in cancer immunotherapy. Recently, an intratumor stem/progenitor-like CD8+ T cell (Tprog cell) population that mediates the persistence of antitumor responses has been defined, which can further develop into a terminally differentiated CD8+ T cell (Tterm cell) subpopulation with potent cytotoxic functions. Tprog cells are the main responders to immune checkpoint blockade therapies, yet how extrinsic signals via transcription factors control Tprog cell generation and persistence in tumors is unclear. Here, we found that BCL6 inhibits tumor-specific Tterm cell generation from Tprog cell downstream of TCF1. We show that Bcl6 deficiency reduced the persistence of Tprog cells, without affecting their generation, thus abrogating long-term tumor control. High-level BCL6 expression was observed in tumor-specific T cells in draining lymph nodes (LNs) and was associated with T cell exhaustion. This was observed in TOX+TCF1+ Tprog cells in both LNs and tumors. BCL6 expression in CD8+ T cells was up-regulated by TGF-ß-SMAD2 signaling but down-regulated by the IL-2-STAT5 pathway. Mechanistically, BCL6 transcriptionally repressed the expression of Tterm cell-associated genes and induced those of Tprog cell-related genes, in a manner antagonistic to BLIMP1. Prdm1 deficiency also promoted the Tprog cell program and greatly improved the efficacy of anti-PD-1 therapy. Thus, we identified the TGF-ß-BCL6 and IL-2-BLIMP1 antagonistic pathways in regulation of antitumor CD8+ T cells, which may benefit the development of long-lasting and effective cancer immunotherapy.

STAT3 regulates CD8+ T cell differentiation and functions in cancer and acute infection.

In cancer, persistent antigens drive CD8+ T cell differentiation into exhausted progenitor (Texprog) and terminally exhausted (Texterm) cells. However, how the extrinsic and intrinsic regulatory mechanisms cooperate during this process still remains not well understood. Here, we found that STAT3 signaling plays essential roles in promoting intratumor Texterm cell development by enhancing their effector functions and survival, which results in better tumor control. In tumor microenvironments, STAT3 is predominantly activated by IL-10 and IL-21, but not IL-6. Besides, STAT3 also plays critical roles in the development and function of terminally differentiated effector CD8+ T cells in acute infection. Mechanistically, STAT3 transcriptionally promotes the expression of effector function-related genes, while it suppresses those expressed by the progenitor Tex subset. Moreover, STAT3 functions in collaboration with BATF and IRF4 to mediate chromatin activation at the effector gene loci. Thus, we have elucidated the roles of STAT3 signaling in terminally differentiated CD8+ T cell development, especially in cancer, which benefits the development of more effective immunotherapies against tumors.

Tumor-expressed B7-H3 mediates the inhibition of antitumor T-cell functions in ovarian cancer insensitive to PD-1 blockade therapy.

Although PD-L1/PD-1 blockade therapy has been approved to treat many types of cancers, the majority of patients with solid tumors do not respond well, but the underlying reason remains unclear. Here, we studied ovarian cancer (OvCa), a tumor type generally resistant to current immunotherapies, to investigate PD-1-independent immunosuppression. We found that PD-L1 was not highly expressed in the tumor microenvironment (TME) of human OvCa. Instead, B7-H3, another checkpoint molecule, was highly expressed by both tumor cells and tumor-infiltrating antigen-presenting cells (APCs), which correlated with T-cell exhaustion in patients. Using ID8 OvCa mouse models, we found that B7-H3 expressed on tumor cells, but not host cells, had a dominant role in suppressing antitumor immunity. Therapeutically, B7-H3 blockade, but not PD-1 blockade, prolonged the survival of ID8 tumor-bearing mice. Collectively, our results demonstrate that tumor-expressed B7-H3 inhibits the function of CD8+ T cells and suggest that B7-H3 may be a target in patients who are not responsive to PD-L1/PD-1 inhibition, particularly OvCa patients.

[Progress in epigenetic modification of mRNA and the function of m6A modification].

Messenger RNA (mRNA) can be modified by more than 100 chemical modifications. Among these modifications, N6-methyladenosine (m6A) is one of the most prevalent modifications. During the processes of cells differentiation, embryo development or stress, m6A can be modified on key mRNAs and regulate the progress of cells through modulating mRNA metabolism and translation. Other mRNA modifications, including N1-methyladenosine (m¹A), 5-methylcytosine (m5C) and pseudouridine, together with m6A form the epitranscriptome of mRNA that accurately modulate the mRNA translation. Here we review the types and characteristic of mRNA epigenetic modifications, especially the recent progresses of the function of m6A, we also expect the main research direction of m6A epigenetic modification in the future.

Nrf2 is a key factor in the reversal effect of curcumin on multidrug resistance in the HCT­8/5­Fu human colorectal cancer cell line.

Multidrug resistance (MDR) is a major concern when using chemotherapy for the treatment of patients with colorectal cancer. MDR modulators are agents that can reverse MDR and, thus, enhance the chemosensitivity of tumor cells. The development of MDR modulators can improve the therapeutic efficacies of MDR in cancer. However, few effective MDR modulators have been identified so far. Curcumin has been reported to be an effective compound in the reversal of MDR in colorectal cancer cells. However, the mechanisms associated with the reversal effect of curcumin on MDR and its regulation of target factors in MDR cells remain to be fully elucidated. 3­(4,5­dimethyl­2­thiazol)­2,5­diphenyltetrazolium bromide assays, flow cytometer apoptosis assays as well as mRNA and protein expression assays were performed in the present study, and the results confirmed the reversal effect of curcumin on HCT­8/5­Fu cells and provided evidence that activated nuclear factor erythroid 2­related factor (Nrf2) deficiency induced by the curcumin altered the B­cell lymphoma 2 (Bcl­2) associated X protein/Bcl­2 expression ratio, which led to the induction of apoptosis in HCT­8/5­Fu cells. These results indicated that Nrf2 may have a functional in the reversal effect of curcumin and contribute, at least in part, to the outcomes of chemotherapy in patients with MDR.

Ceritinib (LDK378): a potent alternative to crizotinib for ALK-rearranged non-small-cell lung cancer.

The success in identifying the chromosomal rearrangements involving the anaplastic lymphoma kinase (ALK) as an oncogenic driver has thoroughly changed the treatment of non-small-cell lung cancer. In the past decade, targeted drugs have emerged as an efficient personalized strategy for ALK-rearranged non-small-cell lung cancer. The accelerated approval of potent ALK inhibitors, such as crizotinib and more recently ceritinib (LDK378), based on the well designed phase I/II trials has been a landmark success in clinical cancer research and contributes a new era of oncogenic targeted therapy characterized by elegant clinical trial design. In this review, we aim to present the current knowledge on acquired resistance of crizotinib known as a first-in-class ALK inhibitor and potential solutions to improve the cost-effectiveness, and to review the difference between ceritinib and crizotinib; preclinical data and results of the elegant early clinical trial of ceritinib which promoted its accelerated approval, pharmacokinetics, safety profile, and tolerability, the updated results (eg, efficacy on brain metastases), and robust design of ongoing phase II/III trials, and future directions of ceritinib to be a potent alternative to crizotinib for ALK-rearranged non-small-cell lung cancer are also presented.