Cabozantinib-based combination therapy for the treatment of hepatocellular carcinoma

Cabozantinib: An evolving therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is rising in incidence and remains a leading cause of cancer-related death. After a decade of disappointing trials following the approval of sorafenib for patients with advanced HCC, a number of tyrosine kinase inhibitors (TKIs) and monoclonal antibodies targeting angiogenesis and immune checkpoints have recently been approved. The phase 3 CELESTIAL trial demonstrated improved progression-free and overall survival with the TKI cabozantinib compared to placebo, supporting it as a treatment option for patients with advanced HCC previously treated with sorafenib. Cabozantinib blocks multiple key pathways of HCC pathogenesis, including VEGFR, MET, and the TAM (TYRO3, AXL, MER) family of receptor kinases, and promotes an immune-permissive tumor microenvironment. Here, we review the mechanisms of action of cabozantinib, including effects on tumor growth and its immunomodulatory properties, providing pre-clinical rationale for combination strategies with checkpoint inhibitors. We discuss the design and outcomes of CELESTIAL including improved survival across subgroups defined by age, disease etiology, baseline AFP level, prior therapies (including duration of prior sorafenib), and tumor burden. Cabozantinib had a manageable safety profile with dose modification. Studies combining cabozantinib with atezolizumab (COSMIC-312) and durvalumab (CAMILLA) in the first and second-line settings are ongoing, as well as a neoadjuvant study of cabozantinib with nivolumab. Future investigations are warranted to define the use of cabozantinib in patients with Child-Pugh B liver function and identify markers predictive of clinical benefit. The role of cabozantinib in HCC continues to evolve with an anticipated role in immunotherapy combinations.

Distinct functions of transforming growth factor-β signaling in c-MYC driven hepatocellular carcinoma initiation and progression

Dysregulation of transforming growth factor-beta (TGFβ) signaling has been implicated in liver carcinogenesis with both tumor promoting and inhibiting activities. Activation of the c-MYC protooncogene is another critical genetic event in hepatocellular carcinoma (HCC). However, the precise functional crosstalk between c-MYC and TGFβ signaling pathways remains unclear. In the present investigation, we investigated the expression of TGFβ signaling in c-MYC amplified human HCC samples as well as the mechanisms whereby TGFβ modulates c-Myc driven hepatocarcinogenesis during initiation and progression. We found that several TGFβ target genes are overexpressed in human HCCs with c-MYC amplification. In vivo, activation of TGFβ1 impaired c-Myc murine HCC initiation, whereas inhibition of TGFβ pathway accelerated this process. In contrast, overexpression of TGFβ1 enhanced c-Myc HCC progression by promoting tumor cell metastasis. Mechanistically, activation of TGFβ promoted tumor microenvironment reprogramming rather than inducing epithelial-to-mesenchymal transition during HCC progression. Moreover, we identified PMEPA1 as a potential TGFβ1 target. Altogether, our data underline the divergent roles of TGFβ signaling during c-MYC induced HCC initiation and progression.

Loss of Apc Cooperates with Activated Oncogenes to Induce Liver Tumor Formation in Mice

Hepatocellular carcinoma (HCC) and hepatoblastoma are the major types of primary liver cancer in adulthood and childhood, respectively. Wnt/β-catenin signaling deregulation is one of the most frequent genetic events in hepatocarcinogenesis. APC regulator of WNT signaling pathway (APC) encodes an inhibitor of the Wnt cascade and acts as a tumor suppressor. Germline defects of the APC gene lead to familial adenomatous polyposis, and its somatic mutations occur in multiple tumor types. However, the contribution of APC in hepatocarcinogenesis remains unclear. Therefore, APC mutations and expression patterns were examined in human HCC and hepatoblastoma samples. Whether loss of Apc alone or in cooperation with other oncogenes triggers liver tumor development in vivo was also investigated. sgApc alone could not drive liver tumor formation, but synergized with activated oncogenes (YapS127A, TazS89A, and c-Met) to induce hepatocarcinogenesis. Mechanistically, Apc deletion induced the activation of β-catenin and its downstream targets in mouse liver tumors. Furthermore, Ctnnb1 ablation or TCF4-mediated transcription blockade completely prevented liver tumor formation, indicating the requirement of a functional β-catenin pathway for loss of Apc-driven hepatocarcinogenesis. This study shows that a subset of HCC patients with loss-of-function APC mutations might benefit from therapeutic strategies targeting the Wnt/β-catenin pathway.