Stem Cell Origin of Cancer: Clinical Implications for Cancer Immunity and Immunotherapy

A simple way to understand the immune system is to separate the self from non-self. If it is self, the immune system tolerates and spares. If it is non-self, the immune system attacks and destroys. Consequently, if cancer has a stem cell origin and is a stem cell disease, we have a serious problem and a major dilemma with immunotherapy. Because many refractory cancers are more self than non-self, immunotherapy may become an uphill battle and pyrrhic victory in cancer care. In this article, we elucidate cancer immunity. We demonstrate for whom, with what, as well as when and how to apply immunotherapy in cancer care. We illustrate that a stem cell theory of cancer affects our perspectives and narratives of cancer. Without a pertinent theory about cancer's origin and nature, we may unwittingly perform misdirected cancer research and prescribe misguided cancer treatments. In the ongoing saga of immunotherapy, we are at a critical juncture. Because of the allure and promises of immunotherapy, we will be treating more patients not immediately threatened by their cancer. They may have more to lose than to gain, if we have a misconception and if we are on a wrong mission with immunotherapy. According to the stem cell theory of cancer, we should be careful with immunotherapy. When we do not know or realize that cancer originates from a stem cell and has stem-ness capabilities, we may cause more harm than good in some patients and fail to separate the truth from the myth about immunotherapy in cancer care.

Partially randomised patient preference trials as an alternative design to randomised controlled trials: systematic review and meta-analyses

OBJECTIVE

Randomised controlled trials (RCT) are the gold standard to provide unbiased data. However, when patients have a treatment preference, randomisation may influence participation and outcomes (eg, external and internal validity). The aim of this study was to assess the influence of patients' preference in RCTs by analysing partially randomised patient preference trials (RPPT); an RCT and preference cohort combined.

DESIGN

Systematic review and meta-analyses.

DATA SOURCES

MEDLINE, Embase, PsycINFO and the Cochrane Library.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

RPPTs published between January 2005 and October 2018 reporting on allocation of patients to randomised and preference cohorts were included.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers extracted data. The main outcomes were the difference in external validity (participation and baseline characteristics) and internal validity (lost to follow-up, crossover and the primary outcome) between the randomised and the preference cohort within each RPPT, compared in a meta-regression using a Wald test. Risk of bias was not assessed, as no quality assessment for RPPTs has yet been developed.

RESULTS

In total, 117 of 3734 identified articles met screening criteria and 44 were eligible (24 873 patients). The participation rate in RPPTs was >95% in 14 trials (range: 48%-100%) and the randomisation refusal rate was >50% in 26 trials (range: 19%-99%). Higher education, female, older age, race and prior experience with one treatment arm were characteristics of patients declining randomisation. The lost to follow-up and cross-over rate were significantly higher in the randomised cohort compared with the preference cohort. Following the meta-analysis, the reported primary outcomes were comparable between both cohorts of the RPPTs, mean difference 0.093 (95% CI -0.178 to 0.364, p=0.502).

CONCLUSIONS

Patients' preference led to a substantial proportion of a specific patient group refusing randomisation, while it did not influence the primary outcome within an RPPT. Therefore, RPPTs could increase external validity without compromising the internal validity compared with RCTs.

PROSPERO REGISTRATION NUMBER

CRD42019094438.

Heat shock protein vaccines against glioblastoma: from bench to bedside

Current adjuvant treatment regimens available for the treatment of glioblastoma are widely ineffective and offer a dismal prognosis. Advancements in conventional treatment strategies have only yielded modest improvements in overall survival. Immunotherapy remains a promising adjuvant in the treatment of GBM through eliciting tumor specific immune responses capable of producing sustained antitumor response while minimizing systemic toxicity. Heat shock proteins (HSP) function as intracellular chaperones and have been implicated in the activation of both innate and adaptive immune systems. Vaccines formulated from HSP-peptide complexes, derived from autologous tumor, have been applied to the field of immunotherapy for glioblastoma. The results from the phase I and II clinical trials have been promising. Here we review the role of HSP in cellular function and immunity, and its application in the treatment of glioblastoma.

Regulatory T-cell depletion synergizes with gp96-mediated cellular responses and antitumor activity

Despite its potent immunostimulatory properties, vaccination with autologous tumor-derived gp96 has relatively modest antitumor effect in a range of clinical trials. Based on our previous study showing a gp96-mediated immune balance between CTL and Tregs, here we investigated possible synergy between gp96 vaccine and systemic Treg depletion on induction of antitumor T-cell immunity and the mechanisms accounting for synergistic efficacy. In gp96-peptide complex immunized BALB/c mice, anti-CD25 mAb treatment significantly increased IFN-γ-producing CD8(+) and CD4(+) T cells by about 1-2-fold in spleen and 40-50% in lymph node. A significantly higher number of peptide-specific CTL were observed under anti-CD25 mAb treatment compared with no treatment. Moreover, Treg depletion synergistically improved the anticancer activity of tumor-derived gp96 vaccine in the poorly immunogenic and highly tumorigenic B16 melanoma model in C57BL/6 J mice. While gp96 immunization alone led to the modest enhancement of CTL activities in spleen, the combination with Treg depletion dramatically increased tumor-specific CTL responses. In addition, the combination resulted in a significant increase of CD8(+) T-cell infiltration in tumor, which correlated with an enhanced inhibition of tumor growth. Our results provide evidence that targeting Tregs may provide a more efficient strategy to potentiate gp96-mediated T-cell responses and enhance the antitumor efficiency of gp96-based therapeutic vaccine.

Heat shock protein-peptide complex in the treatment of glioblastoma

Vaccination immunotherapies offer the promise of long-term tumor control, and preclinical trials have found promising results. Active immunotherapy uses the adaptive immune response to specifically kill tumor cells. Tumor-specific antigens are processed by antigen-presenting cells and recognized by specific effector lymphocytes. However, basic vaccination strategies with tumor lysates have been unsuccessful in inducing antiglioma immunity in clinical trials. Gliomas are known to modulate the activity of antigen-presenting cells to reduce antitumor immune activity. Recently, tumor-derived heat shock proteins have been found to more effectively activate the immune response. Widely expressed, heat shock proteins are thought to present protein peptide fragments in a format conducive to processing by antigen-presenting cells. As a part of the protein synthesis machinery, peptides complexed with heat shock proteins are effectively representative of antigens expressed by the cell; these peptides convey the specificity of this vaccination strategy. The heat shock protein-peptide vaccine is one of many promising immunotherapeutic strategies being evaluated in clinical trials. These can be broadly classified as active, passive and adoptive, each with advantages and disadvantages. Here, we compare and contrast heat shock protein-peptide vaccines with other immunotherapies and describe the outcomes of clinical trials to date.

The immunological era in melanoma treatment: new challenges for heat shock protein-based vaccine in the advanced disease

INTRODUCTION

Tumor-derived heat shock protein (HSP)-peptide complexes (HSPPCs) induced immunity against malignancies in preclinical trials, working across tumor types and bypassing the need to identify single immunogenic peptides. These results paved the way for the use of human gp96 obtained from autologous tumor samples as an anti-cancer vaccine.

AREAS COVERED

Autologous tumor-derived HSP gp96 peptide complex (HSPPC-96) vaccine is emerging as a tumor- and patient-specific cancer vaccine, with confirmed activity in several malignancies. It has been tested in Phase III clinical trials in advanced melanoma and kidney cancer with evidence for efficacy in patients with earlier stage disease. HSPPC-96-based vaccine demonstrated an excellent safety profile, thus emerging as a novel therapeutic approach with a suggestive role in cancer therapy. This review summarizes work on the use of HSPPC-96 as an autologous anti-tumor vaccine in advanced melanoma. Data were retrieved by PubMed and Medline research and using the authors' personal experience.

EXPERT OPINION

Further investigations are needed to understand the biological basis of immune functions in order to improve the clinical outcome of HSP-based cancer therapy. In the near future, the combination of HSP-based vaccines with other biological compounds might represent a successful strategy in the therapy of advanced melanoma.