Chimeric antigen receptor T cells targeting HERV-K inhibit breast cancer and its metastasis through downregulation of Ras

Abstract

We have previously reported that human endogenous retrovirus-K (HERV-K) envelope () protein is a tumor-associated antigen (TAA) for cancer vaccines, and that its antibodies (mAbs) possess antitumor activity against cancer. In this study, a chimeric antigen receptor (CAR) specific for HERV-K env protein (K-CAR) was generated using anti-HERV-K mAb. K-CAR T cells from peripheral blood mononuclear cells (PBMCs) of 9 breast cancer (BC) patients and 12 normal donors were able to inhibit growth of, and to exhibit significant cytotoxicity toward, BC cells but not MCF-10A normal breast cells. The antitumor effects in cancer cells were significantly reduced when control T cells were used, or the expression of HERV-K was knocked down by an shRNA. Secretion of multiple cytokines, including IFNγ, TNF-α, and IL-2, was significantly enhanced in culture media of BC cells treated with K-CARs. Significantly reduced tumor growth and tumor weight was observed in xenograft models bearing MDA-MB-231 or MDA-MB-435.eB1 BC cells. Importantly, the K-CAR prevented tumor metastasis to other organs. Furthermore, downregulation of HERV-K expression in tumors of mice treated with K-CAR correlated with upregulation of p53 and downregulation of MDM2 and p-ERK. Importantly, the expression of HERV-K env protein in metastatic tumor tissues treated with K-CAR T cells correlated with the expression of Ras. Our results indicate that HERV-K env protein is an oncoprotein and may play an important role in tumorigenesis related to p53 and Ras signaling pathways. Anti-HERV-K treatment, including K-CAR treatment, shows potential for immunotherapy of BC.

Downregulation of Human Endogenous Retrovirus Type K (HERV-K) Viral env RNA in Pancreatic Cancer Cells Decreases Cell Proliferation and Tumor Growth

“…KRAS expression led to activation of JNK in pancreatic cancer cell lines (71). HERV-K control of RAS expression has been reported by us in breast cancer (41,42), and our results in the current study using KRAS mutant Panc-1 cells suggest that HERV-K may induce JNK activation in PCs with KRAS mutation.…”

“…Although HERV-K is the most complete and biologically active family of HERVs, the precise mechanism leading to abnormal HERV gene expression has yet to be clearly understood. Our results below and recent publications [ours (42) (39,41) and others (43)] provide strong evidence that abnormal expression of HERV-K triggers pathological processes leading to cancer onset, and also contributes to the morphological and functional cellular modifications implicated in cancer progression (2–9). HERV-K can express two accessory viral proteins, Rec and NP9, which are believed to have oncogenic potential (44).…”

“…Our laboratory showed that the HERV-K family is active and overexpressed in breast cancer (2,23,37–40): HERV-K expression was detected in 45% to 93% of primary breast tumors (N=479), and a higher rate of lymph node metastasis was associated with HERV-K-positive compared with HERV-K-negative tumors. (23,37,39–41). Although HERV-K is the most complete and biologically active family of HERVs, the precise mechanism leading to abnormal HERV gene expression has yet to be clearly understood.…”

Activation of HERV-K Env protein is essential for tumorigenesis and metastasis of breast cancer cells

“…The overexpression of HERV-K in various breast cancer cell lines has been demonstrated previously [5, 6, 8]. Higher percentages of HERV-K Env protein expression were demonstrated in BC cell lines (Hs578T, MDA-MB-231, MCF-7, MDA-IBC-3, and BT549) than in HEK293 or HEK293T cells by flow cytometry (FACS), cell enzyme-linked immunosorbent assay (ELISA), immunofluorescence staining (IFS), immunohistochemistry (IHC), and immunoblot (data not shown).…”

Human endogenous retroviruses and cancer

“…Other cellular vaccines are prepared using HERV-K Env-specific chimeric antigen receptor (CAR) T-cell vaccines using the Sleeping Beauty system for introducing HERV-K Env-specific CAR derived from mouse monoclonal antibody into T cells 48 . Recombinant cellular vaccines using the modified vaccine virus Ankara expressing HERV-K Env glycoprotein (MVA-HERV-K Env) 49 were also developed, and activity is demonstrated in vitro and in animal models.…”