Preclinical Studies Help to Illuminate Immunotherapy's Role in HCC

Tim F. Greten, MD

Following on their impressive success in the treatment of several other tumor types, immune-based therapies are being studied in clinical trials for hepatocellular carcinoma (HCC) and are showing promising signals of efficacy.

“Very early results from clinical trials indeed suggest a possible role for immunotherapy in the treatment of HCC," said Tim Greten, discussing research being conducted under the auspices of the National Cancer Institute (NCI). Greten, a senior investigator at the NCI’s Center for Cancer Research, Thoracic and Gastrointestinal Branch, reported these findings at the 2016 Annual Liver Meeting of the American Association for the Study of Liver Diseases.

Nonalcoholic fatty liver disease (NAFLD) has been shown to be a precursor to HCC, providing a rationale for a laboratory study examining the effects of diet on NAFLD disease. It is understood that tumor microenvironment and tumor suppressive mechanisms affect tumor growth by suppressing antitumor immunity. NAFLD is considered to play a role in metabolic predisposition to liver cancer by causing selective CD4 T lymphocyte loss. High fat diets cause hepatic C18:2 accumulation that starts the secretion of cytokines, leading to apoptosis of tumor growth and hepatocellular carcinoma.

In 1 study reviewed by Greten, mice overexpressing the MYC oncogene were split into 2 cohorts, one placed on a methionine/choline-deficient (MCD) diet which is rich in fatty acids, and the second group was given a controlled diet.

Investigators found that the percentage of CD4 T cells was lower in mice on the MCD diet versus controls; CD8 T cells remained the same in both cohorts. These findings suggest that patients with NAFLD who eat an MCD diet may “rescue” the tumor, and a controlled diet may be beneficial in tumor control, Greten reported.

In another preclinical study, in vitro and in vivo testing was performed on CD4 and CD8 T cells to examine the effects of N-acetyl cytein (NAC, also known as acetylcysteine) treatment. NAC has multiple uses, including treatment for acetaminophen overdose and to loosen thick mucus in cystic fibrosis and chronic obstructive pulmonary disease. This study had 1 control and 3 mice cohorts: MCD diet only, MCD and NAC, and an anti-CD4 group with MCD and NAC. Results indicated that NAC treatment may prevent CD4 T cell loss and increase the percentage of necrotic 7AAD+ cells.

This research suggests that in mouse models, as well as human blood and tissue samples, dysregulation of lipid metabolism in NAFLD causes a selective loss of intrahepatic CD4+, but not CD8+ T lymphocytes, leading to accelerated hepatocarcinogenesis.

Myeloid derived suppressor cells (MDSC) also were analyzed in patients, and CD14 increases were observed in patients with HCC. MDSC also inhibited natural killer (NK) cell function which was discovered through evaluating lysis and interferon-γ release. NK cells are important effectors of innate immunity, according to Greten, and the evidence from this study suggest a critical role for NK cells in the immune responses that can be measured and detected in patients with HCC.

Greten noted that these laboratory studies using mice models and patient blood at NCI provide an important foundation and will continue alongside trials exploring the clinical experience of patients with HCC.

A phase I/II proof-of-concept study is evaluating combined locoregional therapy and the anti—CTLA4 monoclonal antibody tremelimumab in HCC. The study enrolled 32 patients with biopsy-confirmed HCC with Childs Pugh A/B7 scores and Barcelona Clinical Liver Cancer stage B or C scores. Most of the participants had already received prior sorafenib (Nexavar); other previous interventions included transarterial chemoembolization (TACE; n = 11), surgery (n = 5), and ablation (n = 5). The group had a median age of 61 years (range, 36-76).

Among 23 patients treated with 10 mg/kg of tremelimumab, the combination therapy demonstrated a median time to progression of 7.4 months and median overall survival (OS) of 13.6 months, Greten said. The OS benefit was more pronounced among patients who received TACE (n = 11); the median OS was not reached, as opposed to a median OS of 10.1 months for participants who were given radiofrequency ablation (n = 12).

Additionally, 3 studies of immunotherapies in HCC all have shown positive responses and promising survival outcomes. “All 3 studies [two involving tremelimumab and 1 nivolumab] demonstrated early signals of efficacy which is a key point,” Greten stressed, in further immunotherapy development.

These results from both the laboratory and the clinic, he concluded, indicate that onco-immunotherapy is promising in HCC. Further research will focus on personalization of immunotherapy, because, as Greten stated “personalization of HCC immunotherapy will decrease expenses and prevent time lapse between diagnosis and effective treatment.”

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Greten also explained how senescence is a tumor-suppressive mechanism that arrests cells at risk for malignant transformation. The NRAS biomarker is stimulated by senescence cells that release cytokines and can have destructive effects on the tissue microenvironment. The most significant of these effects is the acquisition of a senescence-associated secretory phenotype (SASP)—induced immune cells that accumulate in the liver and release CC chemokine receptor (CCR2) and immature mast cells. Senescent fibroblasts become proinflammatory cells that have the ability to promote tumor progression. The survival rate with peritumoral senescence is associated with poor survival.