Interferon induction in cancer: with some observations on the clinical effects of poly 1:C

Overcoming Intrinsic Resistance of Cancer Cells to CAR T-Cell Killing

In the past few years, chimeric antigen receptor (CAR) T-cell therapy has emerged as a promising treatment for cancers that failed standard treatments. Such therapies have already been approved in several blood cancers, such as B-cell leukemia and lymphoma. Despite this progress, a significant proportion of patients experience primary or secondary resistance to CAR T-cell therapy. Here, we review the mechanisms by which CAR T cells eliminate their target and how cancer cells may be insensitive to such killing (here referred to as intrinsic resistance). Recent studies suggest that the activation of apoptosis through death receptor signaling is responsible for a major part of CAR T-cell cytotoxicity in vivo Indeed, cancer cells harboring aberrant apoptotic machinery may be insensitive to CAR T-cell killing. This intrinsic resistance of cancer cells to CAR T-cell killing could be responsible for a significant portion of treatment failure. Finally, we discuss strategies that may be envisioned to overcome such resistance to enhance CAR T-cell efficacy.

Interferons as inducers of apoptosis in malignant cells

Discovered as antiviral cytokines, interferons (IFNs) are now also recognized for their capacity to inhibit the growth of malignant cells via activation of programmed cell death, better known as apoptosis. In this review, we will cover recent advances made in this field, as it pertains to the various proposed mechanisms of IFN-induced apoptosis and the characterization of IFN-responsive genes not previously known to have apoptotic function. Also mentioned here is a description of the activation and crosstalk of survival signaling pathways as a mode of IFN resistance that remains a persistent clinical adversary to overcome and the future of IFNs as antitumor agents.

Biologic response modifiers and urologic malignancies

Biologic response modifiers represent a new generation of immunotherapeutic agents. Although biologic response modifiers such as interferon have been moderately successful in treating B-cell malignancies, they have not been as successful for the management of advanced genitourinary malignancies. The measurement of biologic response modifiers in the urine may prove useful for directing intravesical BCG therapy for the treatment of superficial bladder cancer or for directing the use of prophylactic antibiotics for the management of urinary tract infections.

Randomized trial of standard therapy with or without poly I:C in patients with superficial bladder cancer

Thirty-two patients with superficial urinary bladder tumors were stratified for four variables and randomized after complete transurethral resection and/or fulguration of tumor to receive standard therapy with or without intravenous Poly I:C. Cystoscopies were performed at three- to four-month intervals for up to 48 months. While there was no statistically significant difference in the tumor recurrence rates in the two groups during the first year, a significant increase (P = 0.003) in survival at four years was observed between the Poly I:C group and the control group. The difficulties in evaluating the efficacy of anti-neoplastic agents in the treatment of superficial bladder tumors are discussed.

Viral oncolysate in the management of malignant melanoma. I. Preparation of the oncolysate and measurement of immunologic responses

Primary explants of human malignant melanoma were utilized in the preparation of oncolysates by Newcastle disease virus. The concentrated lysate, administered parenterally, was employed in an effort to augment antitumor immunologic responses in patients with metastatic melanoma. Observed cellular changes suggested a benefit, but humoral antibody measurements were not impressive.

Pharmacologic effects of polyinosinic-polycytidylic acid in man

Twenty-four patients with cancer and concomitant infections with either herpes virus hominis or varicella zoster virus were treated with polyinosinic-polycytidylic acid (rIn.rCn) to determine: 1) the reliability of rIn.rCn to induce interferon production, and 2) the toxicity of the drug. Seven additional patients with herpes zoster were observed as controls. Two lots of rIn.rCn were used; Lot 1 was consistently effective in stimulating serum interferon at doses of 9 and 12 mg/kg, whereas Lot 2 was effective at doses of 3-12 mg/kg. There was no correlation between rIn.rCn doses within these ranges and the resultant interferon levels. Generally, peak serum interferon occurred within the first day. Toxicity to rIn.rCn consisted of fever in 21/24 patients, mild elevation of liver enzymes in 8/24 patients, and laboratory abnormalities of coagulation in 9 patients. The coagulation abnormalities appeared linearly related to the dose of rIn.rCn used. All these abnormalities were reversible, and none were considered severe of life-threatening. Since rIn.rCn was effective in stimulating interferon and since toxicity was considered acceptable, a randomized double-blind study was initiated to determine whether rIn.rCn is effective in the treatment of herpes zoster.

Induction of interferon by polyribonucleotides containing thiopyrimidines

The influence of thioketo substitution in pyrimidine bases of double-stranded polynucleotides on interferon induction was investigated. The stabilizing effect of 2-thioketo substitution was reflected in the increased interferon inducing activity of poly(A-s2U) over that of poly(A-U). Poly(A-s2U) and poly(I)-poly(s2C) were as effective as poly(I)-Poly(C) in rabbit cells. Poly(I)-poly(C) and poly(I)-poly(s2C) were compared in several animal species. No differences in biological effects were observed in rabbits and dogs. In rodents, poly(I)-poly(s2C) was less effective and less toxic.Poly(I)-poly(s2C) was highly resistant against degradation by human serum. Further investigations seem to be justified to elucidate whether this property offers any advantages for the potential clinical utilization of poly(I)-poly(s2C).

Modified polyriboinosinic-polyribocytidylic acid, an immunological adjuvant

Stabilization of polyriboinosinic-polyribocytidylic acid against enzymatic hydrolysis by addition of poly-1-lysine and carboxymethylcellulose (PICLC) resulted in a compound with marked adjuvanticity. The primary antibody response of rhesus monkeys to formalin-inactivated Venezuelan equine encephalomyelitis virus vaccine was significantly potentiated if the vaccine was combined with PICLC prior to vaccination. The antibody response was maintained at a significantly higher level than controls for 2.5 months postvaccination and paralleled immunological responses reported for live, attenuated (TC-83) vaccine.

Interferon administered in the cerebrospinal space and its effect on rabies in rabbits

Because combined administration of intramuscular and intravenous interferon has been partially successful in the incubationary treatment of rabies, the effect of direct interferon administration into the cerebrospinal fluid space was tested. After injecting 1,800 U of interferon into the cisterna magna or the lateral ventricle, periodic samples, obtained by cisternal taps, showed that 1 to 5% remained after 24 h, as opposed to the known clearance of interferon from the bloodstream to this level within minutes. The distributions of interferon and (131)I-labeled albumin were similar as demonstrated by kinetics of clearance monitored over 24 h. Beginning with and after experimental infection of rabbits, daily intraventricular injections of one million units of interferon were given for as long as 3 weeks. Interferon was prepared from cell culture fluids after pressure dialysis and chromatography on Sephadex G-100. This intensive treatment did not prevent encephalitis, but prolonged the length of the incubation period by one- to two-thirds. The outcome after intraventricular administration was not as favorable as when one million units equally divided between intramuscular and intravenous injections were given at the time of challenge. Interferon administered in the subarachnoid space in this fashion is apparently inadequate to protect the rabbit against rabies. Its role as an adjunct measure, or other methods of administration in the nervous system, remains to be examined.