Background
Perturbed lipid metabolism, as observed in non-alcoholic steatohepatitis (NASH), has been linked to the development of hepatocellular carcinoma (HCC). In particular, increased production of oxidized low-density lipoprotein (oxLDL) has been associated with metabolic disturbances and inflammation. Previously, we have demonstrated that immunization with heat-inactivated pneumococci increased the production of anti-oxLDL antibodies, due to molecular mimicry with oxLDL, thereby leading to reduced hepatic inflammation in NASH. However, the effect of anti-oxLDL immunization on the occurrence and progression of NASH to HCC, is currently unexplored.

Methods
In this study, we used a non-alcoholic steatohepatitis (NASH) induced HCC mouse model, in which neonatal male mice were exposed to a low dose streptozotocin (STZ), followed by a high fat diet (HFD) after which all mice developed HCC. To test the effect of immunization against oxLDL on HCC occurrence and progression, mice (n=20) were split into 2 groups either receiving a subcutaneous injection with heat-inactivated Streptococcus pneumonia (10⁸ CFU) or control-injection (0,9% NaCl). Plasma anti-oxLDL titers were measured and tumor growth rate and number of tumors were assessed through CT imaging. Additionally, apoptosis was quantified with TUNEL staining.

Results
Immunization with heat-inactivated Streptococcus pneumonia resulted in increased plasma titers of anti-oxLDL IgM compared to control mice. Immunization reduced both the number of tumors and tumor growth rate compared to control injection. Hepatic TUNEL staining showed increased apoptosis in immunized versus control mice.

Conclusion
Immunization with heat-inactivated Streptococcus pneumonia could potentially be a viable strategy to inhibit progression of NASH-derived HCC.