CpG Island Methylator Phenotype—A Hope for the Future or a Road to Nowhere?

The CpG island methylator phenotype (CIMP) can be regarded as the most notable emanation of epigenetic instability in cancer. Since its discovery in the late 1990s, CIMP has been extensively studied, mainly in colorectal cancers (CRC) and gliomas. Consequently, knowledge on molecular and pathological characteristics of CIMP in CRC and other tumour types has rapidly expanded. Concordant and widespread hypermethylation of multiple CpG islands observed in CIMP in multiple cancers raised hopes for future epigenetically based diagnostics and treatments of solid tumours. However, studies on CIMP in solid tumours were hampered by a lack of generalisability and reproducibility of epigenetic markers. Moreover, CIMP was not a satisfactory marker in predicting clinical outcomes. The idea of targeting epigenetic abnormalities such as CIMP for cancer therapy has not been implemented for solid tumours, either. Twenty-one years after its discovery, we aim to cover both the fundamental and new aspects of CIMP and its future application as a diagnostic marker and target in anticancer therapies.

Combinatorial therapy using RNAi and curcumin nano-architectures regresses tumors in breast and colon cancer models

This novel combination of curcumin (CU)–chitosan (CS) nanocomposites conjugated to Ephb4 shRNA encapsulated with Eudragit S-100 (ES) has been developed to combat breast and colorectal cancers murine models.

COX5B-Mediated Bioenergetic Alterations Modulate Cell Growth and Anticancer Drug Susceptibility by Orchestrating Claudin-2 Expression in Colorectal Cancers

Oxidative phosphorylation (OXPHOS) consists of four enzyme complexes and ATP synthase, and is crucial for maintaining physiological tissue and cell growth by supporting the main bioenergy pool. Cytochrome c oxidase (COX) has been implicated as a primary regulatory site of OXPHOS. Recently, COX subunit 5B (COX5B) emerged as a potential biomarker associated with unfavorable prognosis by modulating cell behaviors in specific cancer types. However, its molecular mechanism remains unclear, particularly in colorectal cancers (CRCs). To understand the role of COX5B in CRCs, the expression and postoperative outcome associations using independent in-house patient cohorts were evaluated. A higher COX5B tumor/nontumor expression ratio was associated with unfavorable clinical outcomes (p = 0.001 and 0.011 for overall and disease-free survival, respectively. In cell-based experiments, the silencing of COX5B repressed cell growth and enhanced the susceptibility of CRCs cells to anticancer drugs. Finally, downstream effectors identified by RNA sequencing followed by RT-qPCR and functional compensation experiments revealed that the tight junction protein Claudin-2 (CLDN2) acts downstream of COX5B-mediated bioenergetic alterations in controlling cell growth and the sensitivity to anticancer drugs in CRCs cells. In conclusion, it was found that COX5B promoted cell growth and attenuated anticancer drugs susceptibility in CRCs cells by orchestrating CLDN2 expression, which may contribute to unfavorable postoperative outcomes of patients with CRCs.

Recurrent Superenhancer of the Oncogene POU5F1B in Colorectal Cancers

Superenhancer usages in single cancer form such as colorectal cancer (CRC) may provide novel efficient targeting candidates. It is unclear whether CRC contains recurrent superenhancers that confer a predisposition to malignancy. We investigated the superenhancer profile of CRC cell line HCT116 and compared it to that of a healthy sigmoid colon. We found that HCT116 had lost most of the normal colon superenhancer activities but gained a new set of tumor-favoring superenhancers that facilitate tumor proliferation, growth signalling, and hypoxia resistance. Inhibiting the superenhancers by JQ-1 treatment had significantly decreased the colony formation capability of HCT116. Then, by comparing the superenhancer genes and robust CRC upregulated genes, we identified a superenhancer associated with a common CRC upregulated oncogene, POU5f1B. POU5f1B overexpression is related to the worse outcome in CRCs. Via performing ChIP-PCR in 35 clinical samples and investigating CRC anti-H3K27ac ChiP-seq public dataset consisting of 36 samples, we further identified that the superenhancer of oncogene POU5F1B is recurrently activated in CRCs, taking 62 and 72 per cent, respectively. Moreover, JQ-1 treatment successfully inhibited the POU5F1B expression in 5 out of 6 POU5F1B superenhancer-positive samples. Therefore, we concluded that the superenhancer activation of POU5F1B contributes partially to its high expression in CRCs, in addition to the well-known gene amplification aetiology.