Frequency and Prognostic Value of IDH Mutations in Korean Patients With Cholangiocarcinoma

Differential isocitrate dehydrogenase 1 and isocitrate dehydrogenase 2 mutation-related landscape in intrahepatic cholangiocarcinoma

BACKGROUND

Patients with intrahepatic cholangiocarcinoma (ICC) are prone to recurrence and poor survival. Targeted therapy related to isocitrate dehydrogenase (IDH) is an extremely important treatment. IDH1 and IDH2 mutations are generally thought to have similar effects on the tumor landscape. However, it is doubtful whether these 2 mutations have exactly the same effects on tumor cells and the tumor microenvironment.

METHODS

All collected tumor samples were subjected to simultaneous whole-exon sequencing and proteome sequencing.

RESULTS

IDH1 mutations accounted for 12.2%, and IDH2 mutations accounted for 5.5%, all missense mutations. Tumors with IDH mutations had lower proportions of KRAS and TP53 mutations. Mutated genes were obviously enriched in the kinase pathway in the tumors with IDH2 mutations. The signaling pathways were mainly enriched in the activation of cellular metabolic activities and an increase of inhibitory immune cells in the tumors with IDH mutations. Moreover, tumors had unique enrichment in DNA repair in IDH1 mutants and secretion of biological molecules in IDH2 mutants. Inhibitory immune cells might be more prominent in IDH2 mutants, and the expression of immune checkpoints PVR and HLA-DQB1 was more prominent in IDH1 mutants. IDH mutants were more related to metabolism-related and inflammation-immune response clusters, and some belonged to the DNA replication and repair cluster.

CONCLUSIONS

These results revealed the differential IDH1 and IDH2 mutation-related landscapes, and we have provided an important reference database to guide ICC treatment.

How to incorporate new agents into precise medicine for cholangiocarcinoma?

Cholangiocarcinoma, a rare and aggressive form of cancer originating from the bile ducts in the liver, poses a significant challenge for treatment. However, the emergence of precision medicine has brought newfound hope for more effective therapies. Several precision medicine approaches have demonstrated promise in the treatment of cholangiocarcinoma. One such approach is targeted therapy, which involves utilizing drugs that specifically target the genetic mutations or alterations present in the tumor cells. In the case of cholangiocarcinoma, mutations in the IDH1 and IDH2 genes are frequently observed. Immunotherapy is another precision medicine approach being explored for the treatment of cholangiocarcinoma. Immune checkpoint inhibitors like pembrolizumab and nivolumab can be used to bolster the body's immune response against cancer cells. While the response to immunotherapy can vary among individuals, studies have shown promising results, particularly in patients with high levels of tumor-infiltrating lymphocytes or microsatellite instability. Moreover, molecular profiling of cholangiocarcinoma tumors can play a crucial role in identifying potential targets for precision medicine. Through advanced next-generation sequencing techniques, specific gene alterations or dysregulations in pathways can be identified, potentially guiding treatment decisions. This personalized approach enables tailored treatment plans based on the unique genetic characteristics of each patient's tumor. In conclusion, the advent of precision medicine has opened up new avenues for the treatment of cholangiocarcinoma. Targeted therapy and immunotherapy have exhibited promising results, and further molecular profiling is expected to uncover additional therapeutic options. Such advancements represent a significant step forward in the quest to enhance outcomes for individuals affected by cholangiocarcinoma.

The regulatory mechanisms and inhibitors of isocitrate dehydrogenase 1 in cancer

Reprogramming of energy metabolism is one of the basic characteristics of cancer and has been proved to be an important cancer treatment strategy. Isocitrate dehydrogenases (IDHs) are a class of key proteins in energy metabolism, including IDH1, IDH2, and IDH3, which are involved in the oxidative decarboxylation of isocitrate to yield α-ketoglutarate (α-KG). Mutants of IDH1 or IDH2 can produce d-2-hydroxyglutarate (D-2HG) with α-KG as the substrate, and then mediate the occurrence and development of cancer. At present, no IDH3 mutation has been reported. The results of pan-cancer research showed that IDH1 has a higher mutation frequency and involves more cancer types than IDH2, implying IDH1 as a promising anti-cancer target. Therefore, in this review, we summarized the regulatory mechanisms of IDH1 on cancer from four aspects: metabolic reprogramming, epigenetics, immune microenvironment, and phenotypic changes, which will provide guidance for the understanding of IDH1 and exploring leading-edge targeted treatment strategies. In addition, we also reviewed available IDH1 inhibitors so far. The detailed clinical trial results and diverse structures of preclinical candidates illustrated here will provide a deep insight into the research for the treatment of IDH1-related cancers.

Recent advances of IDH1 mutant inhibitor in cancer therapy

Isocitrate dehydrogenase (IDH) is the key metabolic enzyme that catalyzes the conversion of isocitrate to α-ketoglutarate (α-KG). Two main types of IDH1 and IDH2 are present in humans. In recent years, mutations in IDH have been observed in several tumors, including glioma, acute myeloid leukemia, and chondrosarcoma. Among them, the frequency of IDH1 mutations is higher than IDH2. IDH1 mutations have been shown to increase the conversion of α-KG to 2-hydroxyglutarate (2-HG). IDH1 mutation-mediated accumulation of 2-HG leads to epigenetic dysregulation, altering gene expression, and impairing cell differentiation. A rapidly emerging therapeutic approach is through the development of small molecule inhibitors targeting mutant IDH1 (mIDH1), as evidenced by the recently approved of the first selective IDH1 mutant inhibitor AG-120 (ivosidenib) for the treatment of IDH1-mutated AML. This review will focus on mIDH1 as a therapeutic target and provide an update on IDH1 mutant inhibitors in development and clinical trials.

Biology of IDH mutant cholangiocarcinoma

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) are the most frequently mutated metabolic genes across human cancers. These hotspot gain-of-function mutations cause the IDH enzyme to aberrantly generate high levels of the oncometabolite, R-2-hydroxyglutarate, which competitively inhibits enzymes that regulate epigenetics, DNA repair, metabolism, and other processes. Among epithelial malignancies, IDH mutations are particularly common in intrahepatic cholangiocarcinoma (iCCA). Importantly, pharmacological inhibition of mutant IDH (mIDH) 1 delays progression of mIDH1 iCCA, indicating a role for this oncogene in tumor maintenance. However, not all patients receive clinical benefit, and those who do typically show stable disease rather than significant tumor regressions. The elucidation of the oncogenic functions of mIDH is needed to inform strategies that can more effectively harness mIDH as a therapeutic target. This review will discuss the biology of mIDH iCCA, including roles of mIDH in blocking cell differentiation programs and suppressing antitumor immunity, and the potential relevance of these effects to mIDH1-targeted therapy. We also cover opportunities for synthetic lethal therapeutic interactions that harness the altered cell state provoked by mIDH1 rather than inhibiting the mutant enzyme. Finally, we highlight key outstanding questions in the biology of this fascinating and incompletely understood oncogene.

Clinicopathologic features and prognosis of olfactory neuroblastoma with isocitrate dehydrogenase 2(IDH2) mutations

OBJECTIVE

Because of their rarity, it is not known whether isocitrate dehydrogenase 2 (IDH2) mutations are related to olfactory neuroblastoma. We investigated relationships between IDH2 mutations, clinicopathological parameters, and prognosis for olfactory neuroblastoma to establish a molecular classification based on IDH2 mutations.

MATERIALS AND METHODS

An 82-patient cohort was retrospectively screened by immunohistochemistry using a mutation-specific IDH2 antibody and by real-time PCR for IDH2 mutations. We also determined immunohistochemically the expression of chromogranin A, synaptophysin, neuron-specific enolase, CD56, S100, and Ki67.

RESULTS

The two methods for detection of IDH2 mutations had high consistency. Mutation of IDH2 detected by real-time PCR was correlated with higher Kadish stage, Hyams grade, and Ki67 proliferation index. Mutation of IDH2 was negatively correlated with expression of chromogranin A, synaptophysin, CD56, and S100. Kaplan-Meier analysis showed that an IDH2 mutation, high Hyams grade, and Ki67 index were associated with poor overall survival. Hyams grade and IDH2 mutation were independent prognostic factors in multivariable analysis.

CONCLUSIONS

Immunohistochemistry was a reliable method to assess the mutation status of IDH2. Tumors with IDH2 mutations represented a distinct subset with aggressive behavior and poor prognosis. The gene status of IDH2 can be a major molecular classification criterion in olfactory neuroblastoma.

Novel biomarkers for cholangiocarcinoma: how can it enhance diagnosis, prognostication, and investigational drugs? Part-1

INTRODUCTION

The development of novel biomarkers for cancer has exploded over the last decade with advances in novel technologies. Cholangiocarcinoma (CCA), a cancer of the bile ducts, has a dearth of strong disease and pathophysiology biomarkers, making early detection and prognostication a difficult task.

AREAS COVERED

In this comprehensive review, we discuss the spectrum of biomarkers for CCA diagnosis and prognostication. We elaborate on novel biomarker discovery through a comprehensive multi-omics approach. We also cover, how certain biomarkers may also serve as unique and potent targets for therapeutic development.

EXPERT OPINION

Despite the relatively poor diagnostic and prognostic performance of existing biomarkers for CCA, there is a vast range of novel biomarkers with exquisite diagnostic and prognostic performance for CCA in the pipeline. Moreover, these biomarkers may serve as potential targets for precision medicine. Existing strategies to target unique biomolecular classes are discussed, within the context of an overall 'omics' focused profiling strategy. Omics profiling will simultaneously allow for enhanced biomarker development and identification of unique subtypes of cholangiocarcinoma and how they are influenced by an individual's unique context. In this manner, patient management strategy and clinical trial design can be optimized to the individual.