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.

It is finally time for adjuvant therapy in melanoma

Although melanoma is amenable to early detection, there has been no decline in the mortality rate of this disease and the prognosis of patients with high-risk primary melanoma or with macroscopic nodal involvement remains poor. The best option for patients with higher-risk melanoma is to receive effective adjuvant therapy in order to reduce their chances of recurrence. Multiple systemic therapeutic agents have been tested as adjuvant therapy for melanoma with durable benefits seen only with interferon- to date. More recently ipilimumab at the high dose of 10 mg/kg has shown a significant improvement in terms of Relapse free survival and Overall survival for stage III melanoma patients but at a significant cost in terms of immune-related toxicities. More recently, novel treatment options have emerged. The results from the latest trials with immunotherapy (PD-1 inhibitors) and molecular targeted therapy (BRAF inhibitor + MEK inhibitor) have revolutionized the management of adjuvant treatment for melanoma. As the results from these trials will mature in the next years, a change in the landscape of adjuvant treatment for melanoma is expected, resulting in new challenges in treatment decisions such as optimizing patients' selection through predictive and prognostic biomarkers, and management of treatment related adverse events, in particular immune related toxicities.

Melanoma adjuvant therapy

Adjuvant therapy targets melanoma micrometastases in patients with surgically resected disease that carry a high risk of death from melanoma recurrence. In this setting, adjuvant therapy provides the greatest opportunity for cure before progression into advanced inoperable stages. In randomized clinical trials, interferon-alfa has been shown to have a significant impact on relapse-free survival and, at high dosage, on overall survival compared with observation (E1684) and the GMK vaccine (E1694). This article reviews melanoma adjuvant therapy along with the ongoing and planned clinical trials.

Unique pulmonary antigen presentation may call for an alternative approach toward lung cancer immunotherapy

Unlike other tumors, lung cancer appears to be poorly sensitive to immunotherapy. We have recently demonstrated an alternative pathway of lung cancer immunosurveillance. Our data indicate a failure of the adaptive immune system to mediate the immunosurveillance of lung cancer and emphasize the prominent role of natural killer cells in this setting.

Advances in adjuvant therapy: potential for prognostic and predictive biomarkers

Melanoma is the third most common skin cancer but accounts for the majority of skin cancer-related mortality. The rapidly rising incidence and younger age at diagnosis has made melanoma a leading cause of lost productive years of life and has increased the urgency of finding improved adjuvant therapy for melanoma. Interferon-α was approved for the adjuvant treatment of resected high-risk melanoma following studies that demonstrated improvements in relapse-free survival and overall survival that were commenced nearly 30 years ago. The clinical benefits associated with this agent have been consistently observed across multiple studies and meta-analyses in terms of relapse rate, and to a smaller and less-consistent degree, mortality. However, significant toxicity and lack of prognostic and/or predictive biomarkers that would allow greater risk-benefit ratio have limited the more widespread adoption of this modality.Recent success with targeted agents directed against components of the MAP-kinase pathway and checkpoint inhibitors have transformed the treatment landscape in metastatic disease. Current research efforts are centered around discovering predictive/prognostic biomarkers and exploring the options for more effective regimens, either singly or in combination.

Toll-like receptor agonists: current status and future perspective on their utility as adjuvants in improving anticancer vaccination strategies

Toll-like receptor (TLR) agonists possess remarkable properties, particularly with regard to dendritic cell activation, promoting Th1-type cytokine production and optimizing cytotoxic T-cell responses. Preclinical and clinical studies conducted to date show that TLR agonists can improve currently applied anticancer vaccination protocols. Although these have resulted in the US FDA approval of three TLR agonists for use in humans, their abundant application encounters limitations, principally due to dose-limiting toxicity evoking from systemic cytokine production. Here, using selected examples of clinical studies, we provide a concise review regarding the knowledge acquired thus far on the adjuvant use of TLR agonists as cancer vaccine components. We also provide evidence on the exploitation of a novel TLR agonist, prothymosin-α, which enhances the efficacy of tumor-reactive effectors without causing severe adverse effects.

Adjuvant therapy: melanoma

With an incidence that is increasing at 2–5% per year, cutaneous melanoma is an international scourge that disproportionately targets young individuals. Despite much research, the treatment of advanced disease is still quite challenging. Immunotherapy with high-dose interferon-α2b or interleukin-2 benefits a select group of patients in the adjuvant and metastatic settings, respectively, with significant attendant toxicity. Advances in the biology of malignant melanoma and the role of immunomodulatory therapy have produced advances that have stunned the field. In this paper, we review the data for the use of interferon-α2b in various dosing ranges, vaccine therapy, and the role of radiotherapy in the adjuvant setting for malignant melanoma. Recent trials in the metastatic setting using anticytoxic T-lymphocyte antigen-4 (anti-CTLA-4) monoclonal antibody therapy and BRAF inhibitor therapy have demonstrated clear benefit with prolongation of survival. Trials investigating combinations of these novel agents with existing immunomodulators are at present underway.