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Chronic infection is one of the major causes of cancer, and there are several mechanisms for infection‐mediated oncogenesis. Some pathogens encode gene products that behave like oncogenic factors, hijacking cellular pathways to promote the survival and proliferation of infected cells in vivo. Some of these viral oncoproteins trigger a cellular damage defense response leading to senescence; however, other viral factors hinder this suppressive effect, suggesting that cooperation of those viral factors is important for malignant transformation. Coinfection with multiple agents is known to accelerate cancer development in certain cases. For example, parasitic or bacterial infection is a risk factor for adult T‐cell leukemia‐lymphoma induced by human T‐cell leukemia virus type 1, and Epstein‐Barr virus and malaria are closely associated with endemic Burkitt lymphoma. Human immunodeficiency virus type 1 infection is accompanied by various types of infection‐related cancer. These findings indicate that these oncogenic pathogens can cooperate to overcome host barriers against cancer development. In this review, the authors focus on the collaborative strategies of pathogens for oncogenesis from two different points of view: (i) the cooperation of two or more different factors encoded by a single pathogen; and (ii) the acceleration of oncogenesis by coinfection with multiple agents. Oncogenic pathogens have collaborative strategies to overcome host barriers against cancer development.

Human T cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus responsible for the development of adult T-cell leukemia (ATL). Although HTLV-1 harbors an oncogene, tax , that transforms T cells in vitro and induces leukemia in transgenic mice, tax expression is frequently disrupted in ATL, making the oncogenesis of ATL a bit mysterious. The HTLV-1 bZIP factor (HBZ) gene was discovered in 2002 and has been found to promote T-cell proliferation and cause lymphoma in transgenic mice. Thus HBZ has become a novel hotspot of HTLV-1 research. This review summarizes the current findings on HBZ with a special focus on its potential links to the oncogenesis of ATL. We propose viewing HBZ as a critical contributing factor in ATL development.

Human T‐cell leukemia virus type 1 (HTLV‐1) establishes chronic infection in humans and induces a T‐cell malignancy called adult T‐cell leukemia‐lymphoma (ATL) and several inflammatory diseases such as HTLV‐1‐associated myelopathy/tropical spastic paraparesis (HAM/TSP). Persistent HTLV‐1 infection is established under the pressure of host immunity, and therefore the immune response against HTLV‐1 is thought to reflect the status of the disease it causes. Indeed, it is known that cellular immunity against viral antigens is suppressed in ATL patients compared to HAM/TSP patients. In this study, we show that profiling the humoral immunity to several HTLV‐1 antigens, such as Gag, Env, and Tax, and measuring proviral load are useful tools for classifying disease status and predicting disease development. Using targeted sequencing, we found that several carriers whom this profiling method predicted to be at high risk for developing ATL indeed harbored driver mutations of ATL. The clonality of HTLV‐1‐infected cells in those carriers was still polyclonal; it is consistent with an early stage of leukemogenesis. Furthermore, this study revealed significance of anti‐Gag proteins to predict high risk group in HTLV‐1 carriers. Consistent with this finding, anti‐Gag cytotoxic T lymphocytes (CTLs) were increased in patients who received hematopoietic stem cell transplantation and achieved remission state, indicating the significance of anti‐Gag CTLs for disease control. Our findings suggest that our strategy that combines anti‐HTLV‐1 antibodies and proviral load may be useful for prediction of the development of HTLV‐1‐associated diseases. Combined analysis of anti‐HTLV‐1 antibodies and proviral load can efficiently divide ATL and HAM cases into different groups. This strategy may be useful for prediction of the development of HTLV‐1‐associated diseases.

Human T-cell leukemia virus type 1 (HTLV-1) is derived from simian T-cell leukemia virus type 1 (STLV-1), and together they form a broader category known as primate T-cell leukemia virus type 1 (PTLV-1). PTLV-1 encodes multiple proteins from overlapping open reading frames (ORFs) in the pX region. This study aims to characterize the conservation of these proteins in different PTLV-1 subtypes and their role in pathogenesis. For the first time, we report the full-length proviral sequence of an STLV-1 strain isolated from chimpanzee and African green monkey. Phylogenetic analysis reveals high conservation of the accessory proteins p12, p30, and p13 in the HTLV-1a subtype. Conversely, some African PTLV-1 subtypes exhibit loss of ORFs for p12 or p13. For Asian subtypes, simian strains often lack p12, p13, or p30 proteins, whereas human strains retain the ORFs of p30 and p13 but not p12. To assess the infectivity of a simian strain of PTLV-1 lacking ORFs for p12, p13, and p30, we constructed a molecular clone from a naturally infected Japanese macaque (Mfu: Macaca fuscata ) and compared it with HTLV-1a. Using a reporter assay and ELISA, we found similar infectivity to Jurkat T cells; however, STLV-1 Mfu exhibited impaired infectivity in the monocytic cell line THP-1. Additionally, despite the conservation of the HTLV-1/STLV-1 bZIP factor (HBZ/SBZ) ORFs, HBZ/SBZ proteins derived from HTLV-1a and African PTLV-1 subtypes induce significantly higher activation of the TGF-β/Smad signaling pathway than those from Asian subtypes. Collectively, our findings suggest that the acquisition of the accessory proteins by PTLV-1 subtypes potentially confers an advantageous adaptation of PTLV-1 during infection in apes, including humans. Moreover, among PTLV-1 strains, HBZ/SBZ had varying degrees of activity on the TGF-β/Smad pathway; this fact underscores the complex interplay between viral proteins and host signaling pathways, possibly influencing the viral pathogenicity in different species.

T-cell lymphomas (TCLs) are generally associated with a poorer prognosis compared to B-cell lymphomas, and allogeneic hematopoietic cell transplantation (allo-HCT) is often considered for eligible patients. One of the primary reasons for the inferior outcomes in TCLs has been the lack of effective novel agents for many years, resulting in a continued reliance on traditional cytotoxic chemotherapy regimens. However, over the past decade, several novel agents with promising efficacy against TCLs have been developed. Notably, many of these agents not only exert direct anti-tumor effects but also modulate host immune function, raising clinical questions regarding the optimal integration of these agents with allo-HCT. In this review, we aim to summarize how the use of novel agents that are approved for the treatment of TCLs—such as mogamulizumab, brentuximab vedotin, lenalidomide, histone deacetylase inhibitors, enhancer of zeste homolog inhibitors, and immune checkpoint inhibitors—before or after allo-HCT may impact transplantation outcomes in patients with TCLs.

Serum immunofixation electrophoresis (IFE) is often performed for screening monoclonal proteins (M proteins) in immunoglobulin light-chain amyloidosis (AL amyloidosis). However, the performance of serum IFE for detecting M protein in AL amyloidosis patients is often insufficient. In this study, we examined the detection rate of serum M protein in newly diagnosed AL amyloidosis patients and analyzed differences in M protein detection between IFE methods. Among 60 patients newly diagnosed with AL amyloidosis, 22 had undetectable serum M protein by IFE with the Epalyzer2 system. Samples with undetectable M protein had significantly lower involved serum-free light-chain (iFLC) and a smaller difference between involved and uninvolved serum-free light-chain (dFLC) values than samples with IFE-detectable monoclonal light chains. When samples that tested negative for M protein by the Epalyzer2 system were retested by IFE with the HYDRASYS 2 system, 50% had IFE-detectable monoclonal light chains. The IFE system and reagents used may affect serum monoclonal immunoglobulin light-chain detection in AL amyloidosis patients, especially those with low iFLC or low dFLC samples. More attention should be paid to the performance of IFE systems, since it may affect the diagnostic and therapeutic evaluation of AL amyloidosis patients.

Human retroviruses, including human T cell leukemia virus type 1 (HTLV-1) and HIV type 1 (HIV-1), encode an antisense gene in the negative strand of the provirus. Besides coding for proteins, the messenger RNAs (mRNAs) of retroviral antisense genes have also been found to regulate transcription directly. Thus, it has been proposed that retroviruses likely localize their antisense mRNAs to the nucleus in order to regulate nuclear events; however, this opposes the coding function of retroviral antisense mRNAs that requires a cytoplasmic localization for protein translation. Here, we provide direct evidence that retroviral antisense mRNAs are localized predominantly in the nuclei of infected cells. The retroviral 3′ LTR induces inefficient polyadenylation and nuclear retention of antisense mRNA. We further reveal that retroviral antisense RNAs retained in the nucleus associate with chromatin and have transcriptional regulatory function. While HTLV-1 antisense mRNA is recruited to the promoter of C-C chemokine receptor type 4 (CCR4) and enhances transcription from it to support the proliferation of HTLV-1–infected cells, HIV-1 antisense mRNA is recruited to the viral LTR and inhibits sense mRNA expression to maintain the latency of HIV-1 infection. In summary, retroviral antisense mRNAs are retained in nucleus, act like long noncoding RNAs instead of mRNAs, and contribute to viral persistence.

Exophiala dermatitidis ( E. dermatitidis ), which causes skin or respiratory disease, is occasionally fatal in immunocompromised patients. Here, we report the unique antifungal potency of terbinafine (TRB), which targets squalene epoxidase, against E. dermatitidis (SQLE ED ) using various in vitro approaches. The versatile antifungal activities, including fungicidal activity, biofilm formation inhibition, biofilm eradication activity, and the combination effect of TRB, posaconazole (PSC), and amphotericin B (AmB) with great antifungal potency against E. dermatitidis were evaluated using crystal violet and cell viability assay. TRB formed an H-bond through Y102 in SQLE ED in the binding model. E. dermatitidis hyphae elongated and attached to a cell scaffold, forming a membrane-like biofilm. TRB and PSC showed more potent antibiofilm activities than AmB, and exhibited post-antifungal effects without incubation against E. dermatitidis conidia, reducing growth at lower concentrations. In contrast, AmB exhibited strong dose- and time-dependent killing and biofilm-eradication activities. The combination of TRB and PSC was more effective than that of TRB and AmB or PSC and AmB. Although the tissue migration of TRB must be considered, these data suggest that TRB and PSC may be useful agents and a potent combination in severely immunocompromised patients with refractory and systemic E. dermatitidis infection.

Diffuse large B‐cell lymphoma (DLBCL) is the most common subtype of lymphoma, accounting for 30% of non‐Hodgkin lymphomas. Although comprehensive analysis of genetic abnormalities has led to the classification of lymphomas, the exact mechanism of lymphomagenesis remains elusive. The Ets family transcription factor, PU.1, encoded by Spi1, is essential for the development of myeloid and lymphoid cells. Our previous research illustrated the tumor suppressor function of PU.1 in classical Hodgkin lymphoma and myeloma cells. In the current study, we found that patients with DLBCL exhibited notably reduced PU.1 expression in their lymphoma cells, particularly in the non‐germinal center B‐cell‐like (GCB) subtype. This observation suggests that downregulation of PU.1 may be implicated in DLBCL tumor growth. To further assess PU.1's role in mature B cells in vivo, we generated conditional Spi1 knockout mice using Cγ1‐Cre mice. Remarkably, 13 of the 23 knockout mice (56%) showed splenomegaly, lymphadenopathy, or masses, with some having histologically confirmed B‐cell lymphomas. In contrast, no wild‐type mice developed B‐cell lymphoma. In addition, RNA‐seq analysis of lymphoma cells from Cγ1‐Cre Spi1F/F mice showed high frequency of each monoclonal CDR3 sequence, indicating that these lymphoma cells were monoclonal tumor cells. When these B lymphoma cells were transplanted into immunodeficient recipient mice, all mice died within 3 weeks. Lentiviral‐transduced Spi1 rescued 60% of the recipient mice, suggesting that PU.1 has a tumor suppressor function in vivo. Collectively, PU.1 is a tumor suppressor in mature B cells, and decreased PU.1 results in mature B‐cell lymphoma development. PU.1, particularly the non‐germinal center B‐cell‐like (GCB) type, is downregulated in human lymphoma cells. Conditional knockout of Spi1 in mature B cells induces B cell lymphoma in mice.

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy (HAM) after a long latent period in a fraction of infected individuals. These HTLV-1-infected cells typically have phenotypes similar to that of CD4 + T cells, but the cell status is not well understood. To extract the inherent information of HTLV-1-infected CD4 + cells, we integratively analyzed the ATAC-seq and RNA-seq data of the infected cells. Compared to CD4 + T cells from healthy donors, we found anomalous chromatin accessibility in HTLV-1infected CD4 + cells derived from ATL cases in terms of location and sample-to-sample fluctuations in open chromatin regions. Further, by focusing on systematically selected genes near the open chromatin regions, we quantified the difference between the infected CD4 + cells in ATL cases and healthy CD4 + T cells in terms of the correlation between the chromatin structures and the gene expressions. Based on a further analysis of chromatin accessibility, we detected TLL1 (Tolloid Like 1) as one of the key genes that exhibit unique gene expressions in ATL cases. A luciferase assay indicated that TLL1 has an isoform-dependent regulatory effect on TGF- β . Overall, this study provides results about the status of HTLV-1-infected cells, which are qualitatively consistent across the different scales of chromatin accessibility, transcription, and immunophenotype.