Direct and Natural Killer Cell-Mediated Antitumor Effects of Low-Dose Bortezomib in Hepatocellular Carcinoma

Abstract

Purpose: Hepatocellular carcinoma (HCC) displays particular resistance to conventional cytostatic agents. Alternative treatment strategies focus on novel substances exhibiting antineoplastic and/or immunomodulatory activity enhancing for example natural killer (NK) cell antitumor reactivity. However, tumor-associated ligands engaging activating NK cell receptors are largely unknown. Exceptions are NKG2D ligands (NKG2DL) of the MHC class I-related chain and UL16-binding protein families, which potently stimulate NK cell responses. We studied the consequences of proteasome inhibition with regard to direct and NK cell^mediated effects against HCC. Experimental Design: Primary human hepatocytes (PHH) from different donors, hepatoma cell lines, and NK cells were exposed to Bortezomib. Growth and viability of the different cells, and immunomodulatory effects including alterations of NKG2DL expression on hepatoma cells, specific induction of NK cell cytotoxicity and IFN-g production were investigated. Results: Bortezomib treatment inhibited hepatoma cell growth with IC 50 values between 2.4 and 7.7 nmol/L. These low doses increased MICA/B mRNA levels, resulting in an increase of total and cell surface protein expression in hepatoma cells, thus stimulating cytotoxicity and IFN-g production of cocultured NK cells. Importantly, although NK cell IFN-g production was concentration-dependently reduced, low-dose Bortezomib neither induced NKG2DL expression or cell death in PHH nor altered NK cell cytotoxicity. Conclusions: Low-dose Bortezomib mediates a specific dual antitumor effect in HCC by inhibiting tumor cell proliferation and priming hepatoma cells for NK cell antitumor reactivity. Our data suggest that patients with HCC may benefit from Bortezomib treatment combined with immunotherapeutic approaches such as adoptive NK cell transfer taking advantage of enhanced NKG2D-mediated antitumor immunity.

Clinical Value of Absolute Lymphocyte Counts before Bortezomib-Dexamethasone Therapy in Relapsed Multiple Myeloma Patients

“…Lundqvist et al [6 ]also demonstrated that bortezomib could sensitize murine tumor cells to perforin/granzyme as well as tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis. Another recent study demonstrated that bortezomib can downregulate MHC class I molecules and enhance the sensitivity of myeloma to NK cell-mediated lysis [8], and that bortezomib can also promote upregulation of NKG2D, thereby enhancing NK cell cytotoxicity [24,25]. …”

Resveratrol sensitized leukemia stem cell-like KG-1a cells to cytokine-induced killer cells-mediated cytolysis through NKG2D ligands and TRAIL receptors

“…34 Sodium butyrate, a potent repressor of histone deacetylase (HDAC), could upregulate expression of NKG2D ligand MICA/MICB in HeLa and HepG2 cell lines and increase their susceptibility to NK lysis. 35 Low-dose Bortezomib mediated a specific dual antitumor effect in hepatocellular carcinoma by inhibiting tumor cell proliferation and increasing MICA/B protein expression levels on the surface of hepatoma cells, thus stimulating cytotoxicity of cocultured NK cells, 36 similarly to our findings that RES could improve CIKs-mediated cytolysis by upregulating the cell-surface expression of NKG2D ligands ULBP1-3 in KG-1a cells because after expressions of cell-surface ULBP1-3 were all blocked, cytolysis of CIKs against KG-1a/RES cells decreased. Additionally, our data showed that RES could significantly upregulate the mRNA of MICA/MICB and ULBP1-3 in the KG-1a cells, different from the protein distributions on cell surface.…”

Hepatitis B Virus X Protein (HBx) Is Responsible for Resistance to Targeted Therapies in Hepatocellular Carcinoma: Ex Vivo Culture Evidence

“…20). Bortezomib was also shown to differentially affect the expression of E2F1, p21, and p27 (21) and to mediate a specific dual antitumor effect via natural killer (NK) cell antitumor reactivity (22). An international, multicenter phase II trial (23) and several preclinical studies (24)(25)(26) of bortezomib in HCC patients have been reported.…”