Cancer cells engineered to secrete granulocyte-macrophage colony-stimulating factor using ex vivo gene transfer as vaccines for the treatment of genitourinary malignancies

Abstract

When irradiated and administered intradermally as vaccines, cancer cells engineered to secrete high levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) by gene transfer elicit potent anticancer immune responses in a variety of animal tumor models. Upon vaccination, antigens present in the cancer cells are phagocytosed and processed by skin dendritic cells. These dendritic cells then prime anticancer immune responses by presenting antigenic peptides to T cells. The immune responses generated are capable of eradicating small but lethal cancer cell inocula with minimal toxicity in preclinical animal tumor studies. To develop this vaccination strategy for the treatment of human genitourinary cancers, we have conducted phase I clinical trials using human genitourinary cancer cells as sources of cancer cell antigens. In the first human clinical trial of genetically engineered cancer cell vaccines, a phase I clinical trial of kidney cancer cell vaccines (n = 18), kidney cancer cells were removed at surgery, propagated briefly in vitro, and then genetically modified to secrete high levels of GM-CSF via ex vivo transduction with the retrovirus MFG-GM-CSF. After irradiation, the kidney cancer cells were administered as vaccines to 18 patients with advanced kidney cancers. Vaccine treatment, which caused few side effects, nonetheless appeared to trigger anticancer immune responses manifest as conversion of delayed-type hypersensitivity (DTH) skin responses against irradiated autologous cancer cells after vaccination. Biopsies of vaccine sites yielded findings reminiscent of biopsies from preclinical animal model studies, with evidence of vaccine cell recruitment of dendritic cells, T cells, and eosinophils. One patient with measurable kidney cancer metastases treated at the highest vaccine dose level experienced a partial treatment response. The bioactivity of GM-CSF-secreting autologous cancer cell vaccines was confirmed in a phase I clinical trial for prostate cancer (n = 8). Vaccine cells were prepared from surgically harvested prostate tumors by ex vivo transduction with MFG-GM-CSF in a manner similar to that used for the kidney cancer trial. Vaccine treatment was well tolerated and associated with induction of anticancer immunity as assessed using DTH skin testing. In addition, new antiprostate cancer cell antibodies were detected in serum samples from treated men as a consequence of vaccination. These first clinical trials of GM-CSF-secreting cancer cell vaccines for the treatment of genitourinary cancers have demonstrated both safety and bioactivity, in that very few side effects have been seen and anticancer immune responses have been detected. Future clinical studies will be required to assess vaccine treatment efficacy, refine vaccination dose and schedule, define the appropriate clinical context for the use of such vaccines, and ascertain optimal combinations involving vaccines and other local or systemic anticancer treatments.

Oncolysis of Prostate Cancers Induced by Vesicular Stomatitis Virus in PTEN Knockout Mice

“…Neutrophils (A) and macrophages (B) were counted and presented as average of total cell count ± SEM (n = 3). There was no significant difference between total neutrophil counts in PTEN −/− compared for viral therapy because there are various technically easy routes (e.g., transurethral, transperineal, and transrectal) for viral delivery (36). Here, the effect of oncolytic virus VSV(AV3), which replicates in IFN-defective cells, has been studied in the prostate-specific PTEN −/− mice model (20).…”

IFN Unresponsiveness in LNCaP Cells Due to the Lack of JAK1 Gene Expression

“…In a phase I clinical trial, seven of eight patients vaccinated with autologous irradiated, granulocyte macrophage colony-stimulating factor (GM-CSF)-secreting tumor cells mounted T-cell responses against the untransduced tumor cells (29). Due to the technical challenges of establishing autologous cell lines from surgically resected prostate cancer specimens, other clinical trials are now exploring the use of cytokine-secreting allogeneic tumor cell lines, including the LNCaP cell line, as cancer vaccines (30,31). Preliminary data from a phase I/II trial using the GVAX vaccine, a combination of GM-CSF-secreting LNCaP and PC-3 prostate lines, suggest a therapeutic benefit from this approach (31).…”

Cell encapsulation technology as a novel strategy for human anti-tumor immunotherapy

“…Owing to biosafety concerns, this genetic modification method is preferable over a retroviral infection approach because retroviral infection involves risks of development of competent recombinant retroviral particles in vivo. K562-hGM-CSF cells secreted approximately 3000 ng per 10 6 cells every 24 h, which is higher than previously reported values that range from 42 to 1403 ng per 10 6 cells every 24 h. 19,22,41,42,44,45,47 Although the GM-CSF threshold for an effective immunostimulation effect has been evaluated to be 36 ng per 10 6 cells every 24 h, 48 there are no clearly defined values reported for the site of cell injection. On the other hand, Serafini et al 49 reported that a high-dose of GM-CSF could impair the immune response through the recruitment of myeloid suppressor cells.…”