Evaluating the recent developments in palliative chemotherapy for metastatic colorectal cancer

Exosomal transfer of circ_0006174 contributes to the chemoresistance of doxorubicin in colorectal cancer by depending on the miR-1205/CCND2 axis

Exosomes are the mediators of intercellular signal transduction, and they have been involved in the carcinogenesis and chemoresistance of tumor cells. Herein, we intended to investigate whether circular RNA (circRNA) circ_0006174 can regulate chemoresistance of doxorubicin (DOX) in colorectal cancer via exosomes. Forty-one pairs of normal and CRC (DOX sensitive, n = 16; DOX resistant, n = 25) samples were collected. The resistant cell lines (LoVo/DOX and HCT116/DOX) were constructed by exposure of parental cell lines (LoVo and HCT116) to DOX. The detection of circ_0006174, microRNA-1205 (miR-1205), and cyclin D2 (CCND2) was performed by quantitative real-time polymerase chain reaction (qRT-PCR). Cell Counting Kit-8(CCK-8) was applied for determining the half of inhibitory concentration (IC50) of DOX and cell proliferation. The migration and invasion capacities were analyzed via transwell assay. Exosomes were extracted using ultracentrifugation. Protein levels were determined using western blot. Dual-luciferase reporter assay was used for affirming target interaction. In vivo experiment was performed by establishing xenograft models in mice. Circ_0006174 level was upregulated in DOX-resistant CRC tissues and cells. The downregulation of circ_0006174 inhibited DOX resistance, cell proliferation, migration, and invasion in DOX-resistant CRC cells. Interestingly, the abundant circ_0006174 was enriched in exosomes derived from DOX-resistant CRC cells. Furthermore, circ_0006174 could enhance DOX resistance via the exosomal intercellular transfer. Moreover, we validated the target relation of circ_0006174/miR-1205 or miR-1205/CCND2. The effect of exosomal circ_0006174 on DOX resistance was achieved by upregulating the miR-1205-mediated CCND2. In vivo, knockdown of circ_0006174 also enhanced tumor sensitivity to DOX by targeting miR-1205/CCND2 axis. Altogether, these findings unraveled that circ_0006174-enriched exosomes elevated DOX chemoresistance in CRC by the miR-1205/CCND2 axis. The exosomal circ_0006174 can be used as an available biomarker for the diagnosis of chemoresistance in CRC.

Emerging Role of Immunotherapy for Colorectal Cancer with Liver Metastasis

Colorectal cancer (CRC) is the third most common malignant tumor in the world and the second leading cause of cancer-related deaths, with the liver as the most common site of distant metastasis. The prognosis of CRC with liver metastasis is poor, and most patients cannot undergo surgery. In addition, conventional antitumor approaches such as chemotherapy, radiotherapy, targeted therapy, and surgery result in unsatisfactory outcomes. In recent years, immunotherapy has shown good prospects in the treatment of assorted tumors by enhancing the host's antitumor immune function, and it may become a new effective treatment for liver metastasis of CRC. However, challenges remain in applying immunotherapy to CRC with liver metastasis. This review examines how the microenvironment and immunosuppressive landscape of the liver favor tumor progression. It also highlights the latest research advances in immunotherapy for colorectal liver metastasis and identifies immunotherapy as a treatment regimen with a promising future in clinical applications.