Epithelial-mesenchymal transition (EMT) is an important program in epithelial cancer cells to acquire the motility and invasion, which promotes cancer metastasis to remote organs. EMT is induced by various secreted factors, such as transforming growth factor-β (TGF-β) and epidermal growth factor (EGF). TGF-β ligand activates Smad-dependent and -independent pathways by binding to TGF-β receptors. In Smad-dependent pathway, the activated TGF-β receptor phosphorylates Smad2/3 and accelerates its association with Smad4, leading to their nuclear translocation. Smad2/3-4 complex promotes the expression of EMT-inducing transcription factors, such as Snail and Slug. In Smad-independent pathway, mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/AKT pathways are activated and required for TGF-β-induced EMT. Smad-independent pathway is similar to downstream of receptor tyrosine kinases, and therefore EGFR signaling is known to induce EMT synergize with TGF-β signaling. We explored a new mechanism of EGFR-mediated activation of TGF-β signaling and found that c-Abl kinase activates TGF-β signaling. Based on our proteomic analysis, we identified several TGF-β signaling molecules as nuclear c-Abl substrates, including transcriptional intermediary factor 1-γ (TIF1γ/TRIM33/Ectodermin), a suppressor of TGF-β signaling. c-Abl-mediated phosphorylation of TIF1γ inhibits its binding to Smad3, thereby increasing Smad3's transcriptional activity and promoting EMT. TIF1γ phosphorylation is also involved in the EGFR-caused aberrant activation of TGF-β signaling, suggesting that EGFR/c-Abl pathway activates TGF-β signaling through phosphorylation of nuclear substrates and promotes EMT. Our findings provide new insights into the activation machinery of TGF-β signaling, and further studies are required to clarify the clinical significance of the EGFR/c-Abl pathway in cancer metastasis.

With increasing treatment options for metastatic prostate cancer(mPC), there is a growing attention to circulating tumor cells(CTC)and circulating tumor DNA(ctDNA)as minimally invasive biomarkers to facilitate precision medicine. CTC count and ctDNA abundance have been reported to be prognostic factors. In addition, on-treatment changes in these values might also be associated with the treatment response. Androgen receptor gene alterations, including ligand-binding domain mutations, copy number amplification, or structural rearrangements, are identified in most metastatic castration-resistant prostate cancer(mCRPC)and associated with treatment response to androgen receptor pathway inhibitors. Alterations in different DNA damage repair genes, including BRCA2, ATM, CDK12, or mismatch repair genes, are linked to favorable response to targeted therapies such as poly(adenosine diphosphate-ribose)polymerase(PARP)inhibitors or immune checkpoint inhibitors. Overactivation of the PI3K signaling pathway is mainly caused by PTEN loss, and several clinical trials are underway to assess the treatment effect of the targeted therapies such as Akt inhibitors. To disseminate treatment strategies using CTC and ctDNA in clinical practice, we will require prospective biomarker-driven clinical trials, development of novel targeted therapies, and exploration of other molecular characteristics such as epigenome.

With the development of cancer biology and treatment, it has become essential to search not only for basic information such as histology but also for biomarkers that represent the characteristics of tumors when deciding on a treatment strategy. Circulating tumor cells(CTCs), circulating tumor DNA(ctDNA), exosomes, and microRNAs are present in the blood or other body fluid and reflect the tumor status in real-time. Since liquid biopsy is less invasive and easier to collect, it is almost ready to be applied not only for diagnosis but also for monitoring the acquisition of resistance to treatment in real-time. The number of CTCs has been shown to be a prognostic factor in itself for breast cancer, and ctDNA with whole-genome sequencing of tissue specimens is developed to monitor recurrence using the individualized ctDNA set for each patient. Furthermore, cancer genome profiling tests using ctDNA have been commercialized and can now be used with an insurance reimbursement. The possibility of early diagnosis using blood microRNA has already been reported, and the sensitivity and specificity are currently being verified in a prospective observational with a screening cohort. The liquid biopsy will be essential for future breast cancer treatment.

To implement cancer precision medicine based on genomic alterations, tumor tissue genomic profiling using next generation sequencing(NGS)has been reimbursed in 2019, resulting in simultaneous measurement of multiple biomarkers and genomic abnormalities in clinical practice in Japan. However, NGS analysis of tumor tissue has several limitations, including long turnaround time, and difficulty in capturing heterogeneity and longitudinal genotyping. Recently, liquid biopsy has been developed to assess tumor status by analyzing body fluids, such as blood and urine, without the use of tumor tissue. In particular, analysis of circulating tumor DNA(ctDNA)is one of the most advanced technique for liquid biopsy in the world. Our study demonstrated that ctDNA analysis led the shorter turnaround time and acceleration of the trial enrollment in advanced gastrointestinal cancer compared to tissue analysis. Tissue and ctDNA analysis need to be used based on the characteristics of both assays in cancer precision medicine for patients with advanced gastrointestinal cancer in the future.

The assessment of the ability of tumor cells to present antigens with major histocompatibility complex(MHC)class Ⅰ is essential for understanding the immune microenvironment of tumors and for the appropriate application of immunotherapy such as immune checkpoint inhibitors(ICIs). ICIs are very effective for microsatellite instability-high colorectal cancer(MSI-H CRC), where tumor-infiltrating lymphocytes are abundant. At the same time, decreased expression of MHC class Ⅰ is frequently observed in MSI-H CRC. It is necessary to understand the genomic and epigenomic abnormalities that lead to decreased expression of MHC class Ⅰ. In order to optimize ICI treatment, biomarker discovery is required to select patients who need combination therapy, to determine the appropriate timing of treatment discontinuation, and to identify patients who are at high risk for serious complications. Recent reports on MHC class Ⅰ abnormalities and exploration of biomarkers with a focus on MSI-H CRC will be reviewed.

Epigenetics is the study that involves understanding of the DNA sequence-independent mechanism of transcriptional regulation. The epigenetic regulation of gene expression is exerted via the alteration of chromatin structures through covalent modifications of core histone tails and methylation of CpG dinucleotides. In general, histone acetylation and DNA methylation are associated with transcriptional activation and repression, respectively. Histone methylation offers an additional layer for transcriptional regulation. Epigenetic abnormalities underlie the development of various hematological malignancies; for example, recurrent mutations of the DNA methyltransferase DNMT3A or DNA demethylase TET2 transform hematopoietic stem cells into preleukemic stem cells. Consequently, preleukemic stem cells give rise to T-cell lymphomas, such as angioimmunoblastic T-cell lymphoma and T-cell lymphoblastic lymphoma. Epigenetic alterations could be ideal therapeutic targets; indeed, HDAC inhibitors and DNA demethylating agents have already been used for the treatment of peripheral T-cell lymphomas. It is anticipated that more number of epigenetic drugs would be developed for clinical application in the near future.

Leukemia is caused by uncontrolled proliferation of immature hematopoietic progenitors. MLL fusion proteins, generated by chromosomal translocations, activate a broad range of previously transcribed genes to achieve the same expression profile as that of the parent cell in the daughter cells, thereby promoting self-renewal. Normally, replication of the expression profile only occurs in the hematopoietic stem cells (HSCs). A transactivation system comprised of MLL and AF4/ENL/P-TEFb (AEP) complexes promotes it by reactivating CpG-rich promoters. In the normal hematopoietic development, this system is tightly regulated and progressively suppressed during the course of hematopoietic differentiation so that non-HSC hematopoietic cells would not self-renew. Genetic mutations such as fusions of MLL and AEP components generate a constitutively active form of the MLL transcriptional machinery, which aberrantly promotes self-renewal even in non-HSC hematopoietic cells. In this review, I depict a molecular mechanism of MLL fusion-mediated leukemogenesis from a standpoint that leukemogenesis is driven by aberrant self-renewal that is mediated by hyper-active transcriptional machinery, and introduce several molecularly targeted therapies in the making which specifically perturb this transactivation system.

The etiology and pathogenesis of acute myeloid leukemia (AML) have been elucidated at chromosomal and genetic levels. The classification and prognosis for its treatment has clearly involved specific chromosomal aberrations and genetic mutations. The recent comprehensive genomic analysis represented by next-generation sequencers has led to discovering new genetic mutations in AML. These findings have not only been applied clinically as prognostic factors and MRD markers but also contributed to the development of new molecular-targeting drugs. Many new drugs have already been approved in the USA and Europe, and new stratified treatments have tried to incorporate them. With the advent of venetoclax, treatment strategies, especially for patients with poor prognosis and who are unfit, have been substantially revised, and the maintenance therapy for AML is also being reevaluated in accordance to the National Comprehensive Cancer Network guidelines. This article will review the current status of AML treatment in Japan and according to Western guidelines.

Mutations in the FMS-like tyrosine kinase 3 (FLT3) gene represent the most common genetic alteration in acute myeloid leukemia (AML), identified in approximately one third of patients newly diagnosed with AML. FLT3 internal tandem duplication mutations (FLT3-ITD) are associated with increased relapse and inferior overall survival. Multiple inhibitors of FLT3 signaling have been developed in the last few years with variable kinase-inhibitory properties, pharmacokinetics, and toxicity profiles. At present, two FLT3 inhibitors (gilteritinib and quizartinib) have been approved as monotherapies for relapsed/refractory FLT3-mutated AML in Japan, and many more drugs are currently being researched in clinical trials as monotherapies or in combination with conventional chemotherapy or hypomethylating agents and in various settings, including front line, relapsed/refractory disease, and maintenance therapy after consolidation chemotherapy or allogeneic stem cell transplantation. Despite significant advances, some issues need to be overcome, including the resistance to FLT3 inhibitors and controversies regarding the role of FLT3 inhibitors in maintenance therapies and the role of allogeneic stem cell transplantation in FLT3-mutated AML.

Clonal hematopoiesis (CH) harboring a leukemia-related mutation has been recently found in about 10% of healthy elderly individuals, which has been attracting attention. Although most people with CH do not develop hematological malignancies, some may develop hematological malignancies 10 times more frequently than age-matched controls. On the other hand, compared to age-matched controls, the probability of developing cardiovascular diseases in people with CH is 2-fold, which is thought to shorten the life expectancy. Moreover, one out of four patients with solid cancer and one out of two patients with aplastic anemia, whose mutation profiles overlap with but are distinct from common mutations identified with CH of elderly people, harbor CH. The study of CH has just begun, and there are many unknowns. In an aging society of unprecedented proportions, which is also attracting attention from the society, the establishment of a new research field that investigates CH in the near future is likely.

Almost all genetic abnormalities involved in the occurrence and progression of myelodysplastic syndromes (MDS) and acute myeloid leukemia have been reported within the last decade. The molecular mechanisms of these genetic changes involved in causing dysfunctions in hematopoietic cells have also been clarified in recent years. For MDS, gene mutations of RNA splicing factors and cohesin complex have been shown to trigger not only aberrant RNA splicing or decreased chromatin insulation but also DNA damage response and transcriptional dysregulation through inefficient interaction between promoters and enhancers. Consequently, these newly identified disease-causing mechanisms may be considered potential therapeutic targets.

Leukemias diagnosed in <1-year-old infants generally have an aggressive clinical nature and unique biological characteristics. Acute lymphoblastic leukemia (ALL) in infants is still intractable and difficult to treat as compared with other pediatric ALLs, for which considerable progress in treatment outcomes has been recently achieved. Infant leukemia cells frequently carry chromosome translocations involving the 11q23 locus, resulting in the rearrangement and fusion of the KMT2A (MLL) gene. Among several KMT2A fusion genes, KMT2A-AFF1 (MLL-AF4) fusion is characteristically observed in neonatal and infant ALL, representing a hallmark of poor prognosis. The cytogenetic/molecular abnormalities t (1;22)(p13.3;q13.1)/RBM15-MKL1 and t (8;16)(p11.2;p13.3)/KAT6A-CREBBP (MOZ-CBP) are also well-known in acute myeloblastic leukemia in this population. Although many neonatal leukemias occurring within the first 28 days of birth are refractory, spontaneous remissions are occasionally observed, especially in the case of t (8;16). Therefore, international collaborative studies are necessary to improve understanding and facilitate the development of better treatment for this rare disease. Thus, this study summarizes the recently reported clinical, cytogenetic, and molecular biology aspects of neonatal and infant leukemias.

Waldenström's macroglobulinemia or lymphoplasmacytic lymphoma (WM/LPL) is a rare subtype of indolent B-cell lymphoma with plasmacytic differentiation. Owing to its rarity, the pathogenesis, biology, and standard of care have not been established. In 2012 the MYD88 L265P mutation is proven as the major oncogenesis in WM/LPL; therefore, the pathogenesis and underlying biology of WM/LPL have been drastically explored. Furthermore, treatment options have also been developed, and Bruton's tyrosine kinase (BTK) inhibitor has been recently approved for untreated and relapsed/refractory WM/LPL in August 2020 in Japan. In this article, after a brief review of the clinical and biological characteristics of WM/LPL, we discuss the ideal therapeutic algorithm, including novel BTK inhibitor.

Ph-like acute lymphocytic leukemia (ALL) is a subtype of Ph-negative B precursor ALL, and its gene expression profile is similar to that of Ph+ALL. In recent decades, comprehensive genomic analyses have revealed that Ph-like ALL has two types. The first type is associated with the ABL-class tyrosine kinase fusion gene, and the second type with fusion genes involving cytokine receptors or molecules, including CRLF2, which are correlated with the activation of the JAK/STAT pathway. Based on these findings, tyrosine kinase or JAK inhibitors were found to be effective for Ph-like ALL. Genetic abnormalities identified in Ph-like ALL, except for CRLF2 rearrangement, are quite rare. Thus, functional studies regarding each genomic abnormality are relevant for establishing targeted therapies for Ph-like ALL. To develop a targeted molecular therapy, a functional study of NCOR1-LYN, which is a novel ABL-class fusion gene, was conducted on pediatric patients with Ph-like ALL.

Lymphoma comprises a group of diseases characterized by neoplastic proliferation of mature B, T, and NK cells. This disease entity is widely recognized to be clinically, pathologically, molecularly, and genetically heterogeneous. The classification of lymphomas was classically based on morphology and immunology, but recent dramatic advances in next-generation sequencing technology have revealed various genetic alterations in lymphomas, which influenced the revision of the WHO classification in 2017. Accumulating evidence on genetic alterations has enabled the development of more accurate diagnostic strategies and prognostic markers. Moreover, these findings provide opportunities to exploit new therapeutics that target genetic alterations, which would facilitate the use of precision medicine in lymphomas. Here, we briefly review the fundamental methods of genetic analysis using next-generation sequencing technology and describe the entire scenario of genetic alterations, focusing on the recent major studies that have revealed various genetic alterations in each lymphoma subtype and present a detailed discussion of the results and methods.

Chronic lymphocytic leukemia (CLL) is a rare type of lymphoid malignancy among Japanese. Its clinical course is indolent, and the prognosis is good. The two types of CLL based on the mutation status of the IgH gene V segment have been documented in the literature. Then, the del (17p)/TP53 subtype is emphasized, and the treatment strategy for the three subtypes differs. Recent knowledge on molecular pathogenesis facilitated the usage of Bruton's tyrosine kinase (BTK) and BCL2 inhibitors for the treatment of CLL. A better response can be obtained with the use of these novel agents, resulting in a higher rate of negativity for measurable residual disease (MRD). The treatment strategy based on MRD negativity and the treatment outcomes of CLL will improve in future.

An 89-year-old female who had been clinically diagnosed with primary lung cancer underwent right upper lobectomy and lymph node dissection(ND2a-2). Postoperative pathological staging revealed a stage ⅡA(pT1bN1M0)adenocarcinoma that was negative for an EGFR mutation. Nineteen months after surgery, the patient developed a mediastinal lymph node metastasis, and radiotherapy was prescribed. Thirty-eight months later, she developed new mediastinal/hilar lymph node metastases and was prescribed pemetrexed(500 mg on day 1 of each of 3 weeks)as the first-line therapy. A complete response was evident after 10 courses. However, she developed grade 3 nausea, and pemetrexed was discontinued. During 10 months of follow-up, no new lesion appeared; therefore, follow-up was discontinued. Ninety-three months after surgery, she was referred to our hospital because an abnormal shadow was apparent on chest roentgenography. A thorough examination revealed pleural dissemination, pulmonary metastases, mediastinal/hilar lymph node metastases, an adrenal metastasis, and bone metastases. Although her performance status(PS)was poor(grade 4), as the diagnosis was ALK fusion gene-positive adenocarcinoma, alectinib(600 mg once daily)was commenced as the second-line therapy. Complete response was achieved 14 months later(ie, 108 months after surgery and 89 months after postoperative recurrence). Thus, an octogenarian patient with poor PS and ALK fusion gene-positive adenocarcinoma exhibited a complete response after treatment with alectinib.

Diffuse midline glioma, H3K27M mutant is a glioma located in the thalamus, brainstem, or spine with the H3K27M mutation, which is a new entity in the 2016 revised WHO classification. The treatment of thalamic glioma(TG)and brainstem glioma(BSG), which includes diffuse midline gliomas, the H3K27M mutant is challenging, and there are no standard therapeutic strategies. It is important to determine the characteristics of these brain tumors. Here, we retrospectively reviewed 31 consecutive patients with TG and BSG who were treated at our institute between January 1994 and May 2018, including methionine-positron emission tomography(MET-PET)data.

Acute lymphoblastic leukemia (ALL) in infants remains an intractable and difficult-to-treat leukemia as compared to other pediatric ALLs, for which considerable progress has been achieved in terms of treatment outcomes in recent years. The leukemic cells in infants with ALL frequently carry chromosome translocations involving 11q23, resulting in the rearrangement and fusion of the MLL (KMT2A) gene. Among many MLL fusion genes, MLL-AF4 (KMT2A-AFF1) fusion is characteristically observed in infants with ALL, representing a hallmark of poor prognosis. In MLL-AF4-positive infants with ALL, first leukemic cells with MLL-AF4 were generated in utero. Analysis of several murine and human leukemia models revealed that the target cells for tumorigenesis by MLL-AF4 were not the hematopoietic progenitor cells of the bone marrow, but the early hematopoietic progenitor cells present in the fetal liver during the embryonic period and possibly the undifferentiated cells prior to the commitment to hematopoietic cells in the fetus. Elucidation of the leukemogenic process of infant ALL with MLL-AF4 may lead to early, pre-symptomatic diagnosis of leukemia, resulting in the improvement of prognosis and prevention of the onset of ALL in infants.

Genetic complexity and heterogeneity have made drug discovery difficult in human malignancies. In the past few years, we aimed to find vulnerabilities in therapy-resistant and refractory acute myeloid leukemia (AML) through integrative analyses of genomic data, clinical information, and results from in vivo/in vitro cell biological assays. Through analyses, we found that the cells of patients with AML show distinct sensitivity/resistance to small inhibiting molecules for anti-apoptosis and cell cycle/division. In particular, AML cells harboring the IDH1/2 mutations were highly sensitive to BCL-2 inhibition, while inhibition of IAP proteins resulted in efficient elimination of AML cells with varied FLT3, NRAS, and CBL mutations. Linking AML-initiating events with appropriate therapeutic strategies through cellular and genomic analyses might be further translated into nonmyeloid malignancies and solid tumors in the future.