Abstract Ectopic hepatocellular carcinoma (EHCC) is an extremely rare neoplasm, especially in the mediastinum, which shares morphologic characteristics with intrahepatic hepatocellular carcinoma (HCC). Its clinical features remain unclear, posing significant diagnostic and therapeutic challenges. The prognosis is also unclear due to its rarity and potential variability. This study reports the first case of EHCC in the mediastinum with subsequent brain metastasis. A 50-year-old man presented with shoulder and chest discomfort persisting for 5 months, accompanied by progressive weight loss and fatigue over the preceding 2 years. Imaging showed a mediastinal mass initially suspected to be lymphoma due to its malignant characteristics. However, histopathological examination identified the lesion as HCC, supported by characteristic immunohistochemical markers, despite normal abdominal imaging. Two months later, the tumor progressed despite intensive radiotherapy, and the patient experienced recurrent seizures. Subsequent brain imaging confirmed multiple intracranial metastases. Unfortunately, the patient died 6 months after diagnosis. The ectopic liver is more susceptible to hepatocarcinogenesis than the main liver; this is attributed to its incomplete functional structure. EHCC can be considered as differential diagnosis of mediastinal masses, even when no intrahepatic HCC is found. The rarity of EHCC in the mediastinum poses difficulties in developing treatment protocols. This case emphasizes the diagnostic challenges and aggressive nature of ectopic HCC and the need for comprehensive management strategies. There are currently no definite guidelines regarding the diagnosis, treatment, and prognosis of EHCC.
ectopic hepatocellular carcinoma ; mediastinum ; metastasis

Acquisition of resistance to anti-cancer drugs is a significant obstacle to effective cancer treatment. Although several efforts have been made to overcome drug resistance in cancer cells, the detailed mechanisms have not been fully elucidated. Here, we investigated whether microRNAs (miRNAs) function as pivotal regulators in the acquisition of anti-cancer drug resistance to 5-fluorouracil (5-FU). A survey using a lentivirus library containing 572 precursor miRNAs revealed that five miRNAs promoted cell survival after 5-FU treatment in human hepatocellular carcinoma Hep3B cells. Among the five different clones, the clone expressing miR-200a-3p (Hep3B-miR-200a-3p) was further characterized as a 5-FU-resistant cell line. The cell viability and growth rate of Hep3B-miR-200a-3p cells were higher than those of control cells after 5-FU treatment. Ectopic expression of a miR-200a-3p mimic increased, while inhibition of miR-200a-3p downregulated, cell viability in response to 5-FU, doxorubicin, and CDDP (cisplatin). We also showed that dual-specificity phosphatase 6 (DUSP6) is a novel target of miR-200a-3p and regulates resistance to 5-FU. Ectopic expression of DUSP6 mitigated the pro-survival effects of miR-200a-3p. Taken together, these results lead us to propose that miR-200a-3p enhances anti-cancer drug resistance by decreasing DUSP6 expression.
Carcinoma, Hepatocellular ; Cell Line ; Cell Survival ; Clone Cells ; Doxorubicin ; Drug Resistance ; Dual Specificity Phosphatase 6* ; Dual-Specificity Phosphatases* ; Ectopic Gene Expression ; Fluorouracil* ; Humans ; Lentivirus ; MicroRNAs

MicroRNAs (miRNAs) are negative regulators of gene expression, and miRNA deregulation is found in various tumors. We previously reported that suppression of adenine nucleotide translocase 2 (ANT2) by short hairpin RNA (shRNA) inhibits hepatocellular carcinoma (HCC) development by rescuing miR-636 expression. However, the tumor-suppressive mechanisms of ANT2 shRNA are still poorly understood in HCC. Here, we hypothesized that miRNAs that are specifically downregulated by ANT2 shRNA might function as oncomiRs, and we investigated the roles of ANT2 shRNA-regulated miRNAs in the pathogenesis of HCC. Our data show that miR-19a and miR-96, whose expression is regulated by ANT2 suppression, were markedly upregulated in HCC cell lines and clinical samples. Ectopic expression of miR-19a and miR-96 dramatically induced the proliferation and colony formation of hepatoma cells in vitro, whereas inhibition of miR-19a and miR-96 reduced these effects. To investigate the in vivo function, we implanted miR-96-overexpressing HepG2 cells in a xenograft model and demonstrated that the increase in miR-96 promoted tumor growth. We also found that miR-19a and miR-96 inhibited expression of tissue inhibitor of metalloproteinase-2. Taken together, our results suggest that ANT2-regulated miR-19a and miR-96 play an important role in promoting the proliferation of human HCC cells, and the knockdown of ANT2 directly downregulates miR-19a and miR-96, ultimately resulting in the suppression of tumor growth.
Carcinoma, Hepatocellular* ; Cell Line ; Ectopic Gene Expression ; Gene Expression ; Hep G2 Cells ; Heterografts ; Humans ; In Vitro Techniques ; MicroRNAs ; Mitochondrial ADP, ATP Translocases ; RNA, Small Interfering* ; Tissue Inhibitor of Metalloproteinase-2