Alleviating oxidative stress in cancer immunotherapy: a role for histamine?

Immune Checkpoint Inhibition in Advanced Non-Clear Cell Renal Cell Carcinoma: Leveraging Success from Clear Cell Histology into New Opportunities

Renal cell carcinoma (RCC) is a histologically heterogeneous disease with multiple subtypes. Clear cell RCC (ccRCC) represents the most common histology and has thus been easiest to study in clinical trials. Non-clear cell RCC (nccRCC) represents about 25% of RCC tumors, with fewer treatment options available, compared to ccRCC, and with poorer outcomes. Non-clear cell RCC tumors are histologically diverse, with each subtype having distinct molecular and clinical characteristics. Our understanding of nccRCC is evolving, with a gradual shift from treating nccRCC as a single entity to approaching each subtype as its own disease with unique features. Due to the scarcity of patients for study development, trials have predominantly combined all nccRCC subtypes and re-purposed drugs already approved for ccRCC, despite the decreased efficacy. We are now in the early stages of a potential paradigm shift in the treatment of nccRCC, with a rapid development of clinical studies with a focus on this subset of tumors. Investigators have launched trials focused on the molecular drivers of tumorigenesis using targeted therapies. Harboring the immunogenicity of some nccRCC subtypes, and based on promising retrospective studies, clinicians have also devised multiple trials using immune checkpoint inhibitors (ICIs), both alone or in combination with targeted therapies, for nccRCC subtypes. We highlight the promising completed and ongoing studies employing ICIs that will likely continue to improve outcomes in patients with nccRCC and propose future potential immunotherapeutic avenues.

Reactive oxygen species induced by therapeutic CD20 antibodies inhibit natural killer cell-mediated antibody-dependent cellular cytotoxicity against primary CLL cells

The antibody-dependent cellular cytotoxicity (ADCC) of natural killer (NK) cells is assumed to contribute to the clinical efficacy of monoclonal antibodies (mAbs) in chronic lymphocytic leukemia (CLL) and other hematopoietic malignancies of B cell origin. We sought to determine whether reactive oxygen species (ROS)-producing monocytes regulate the ADCC of NK cells against primary CLL cells using anti-CD20 as the linking antibody. The monoclonal CD20 antibodies rituximab and ofatumumab were found to trigger substantial release of ROS from monocytes. Antibody-exposed monocytes induced NK cell apoptosis and restricted NK cell-mediated ADCC against autologous CLL cells. The presence of inhibitors of ROS formation and scavengers of ROS preserved NK cell viability and restored NK cell-mediated ADCC against primary CLL cells. We propose that limiting the antibody-induced induction of immunosuppressive ROS may improve the anti-leukemic efficacy of anti-CD20 therapy in CLL.

Mice lacking NCF1 exhibit reduced growth of implanted melanoma and carcinoma tumors

The NADPH oxidase 2 (NOX2) complex is a professional producer of reactive oxygen species (ROS) and is mainly expressed in phagocytes. While the activity of the NOX2 complex is essential for immunity against pathogens and protection against autoimmunity, its role in the development of malignant tumors remains unclear. We compared wild type and Ncf1^m1J mutated mice, which lack functional NOX2 complex, in four different tumor models. Ncf1^m1J mutated mice developed significantly smaller tumors in two melanoma models in which B16 melanoma cells expressing a hematopoietic growth factor FLT3L or luciferase reporter were used. Ncf1^m1J mutated mice developed significantly fewer Lewis Lung Carcinoma (LLC) tumors, but the tumors that did develop, grew at a pace that was similar to the wild type mice. In the spontaneously arising prostate carcinoma model (TRAMP), tumor growth was not affected. The lack of ROS-mediated protection against tumor growth was associated with increased production of immunity-associated cytokines. A significant increase in Th2 associated cytokines was observed in the LLC model. Our present data show that ROS regulate rejection of the antigenic B16-luc and LLC tumors, whereas the data do not support a role for ROS in growth of intrinsically generated tumors.

Effects of reactive nitrogen scavengers on NK-cell-mediated killing of K562 cells

This study explored the effects of reactive nitrogen metabolites (RNMS) on natural-killer- (NK-) cell-mediated killing of K562 cells and the influence of RNM scavengers, such as tiopronin (TIP), glutamylcysteinylglycine (GSH), and histamine dihydrochloride (DHT), on reversing the suppressing effect of RNM. We administered exogenous and endogenous RNM in the NK + K562 culture system and then added RNM scavengers. The concentrations of RNM, TNF-β and IFN-γ, and NK-cell cytotoxicity (NCC) and the percentage of living NK cells were then examined. We found that both exogenous and endogenous RNM caused the KIR to decrease (P < 0.01); however, RNM scavengers such as TIP and GSH rescued this phenomenon dose dependently. In conclusion, our data suggests that RNM scavengers such as TIP and GSH enhance the antineoplasmic activity of NK cells.

T cells expanded in presence of IL-15 exhibit increased antioxidant capacity and innate effector molecules

Persistence of effector cytotoxic T lymphocytes (CTLs) during an immunological response is critical for successfully controlling a viral infection or tumor growth. Various cytokines are known to play an important part in regulating the immune response. The IL-2 family of cytokines that includes IL-2 and IL-15 are known to function as growth and survival factors for antigen-experienced T cells. IL-2 and IL-15 possess similar properties, including the ability to induce T cell proliferation. Whereas long-term IL-2 exposure has been shown to promote apoptosis and limit CD8(+) memory T cell survival and proliferation, it is widely believed that IL-15 can inhibit apoptosis and helps maintain a memory CD8(+) T-cell population. However, mechanisms for superior outcomes for IL-15 as compared to IL-2 are still under investigation. Our data shows that human T cells cultured in the presence of IL-15 exhibit increased expression of anti-oxidant molecules glutathione reductase (GSR), thioredoxin reductase 1 (TXNDR1), peroxiredoxin (PRDX) and superoxide dismutase (SOD). An increased expression of cell-surface thiols, intracellular glutathione, and thioredoxins was also noted in IL-15 cultured T cells. Additionally, IL-15 cultured T cells showed an increase in cytolytic effector molecules. Apart from increased level of Granzyme A and Granzyme B, IL-15 cultured T cells exhibited increased accumulation of reactive oxygen (ROS) and reactive nitrogen species (RNS) as compared to IL-2 cultured T cells. Overall, this study suggests that T cells cultured in IL-15 show increased persistence not only due to levels of anti-apoptotic proteins, but also due to increased anti-oxidant levels, which is complimented by increased cytolytic effector functions.

Individual patient data meta-analysis of randomized trials evaluating IL-2 monotherapy as remission maintenance therapy in acute myeloid leukemia

IL-2 is a natural, T cell-derived cytokine that stimulates the cytotoxic functions of T and natural killer cells. IL-2 monotherapy has been evaluated in several randomized clinical trials (RCTs) for remission maintenance in patients with acute myeloid leukemia (AML) in first complete remission (CR1), and none demonstrated a significant benefit of IL-2 monotherapy. The objective of this meta-analysis was to reliably determine IL-2 efficacy by combining all available individual patient data (IPD) from 5 RCTs (N = 905) and summary data from a sixth RCT (N = 550). Hazard ratios (HRs) were estimated using Cox regression models stratified by trial, with HR < 1 indicating treatment benefit. Combined IPD showed no benefit of IL-2 over no treatment in terms of leukemia-free survival (HR = 0.97; P = .74) or overall survival (HR = 1.08; P = .39). Analyses including the sixth RCT yielded qualitatively identical results (leukemia-free survival HR = 0.96, P = .52; overall survival HR = 1.06; P = .46). No significant heterogeneity was found between the trials. Prespecified subset analyses showed no interaction between the lack of IL-2 effect and any factor, including age, sex, baseline performance status, karyotype, AML subtype, and time from achievement of CR1 to initiation of maintenance therapy. We conclude that IL-2 alone is not an effective remission maintenance therapy for AML patients in CR1.

Monocyte-induced NK cell inactivation: role of reactive oxygen and nitrogen metabolites

Here in a co-cultivation system of natural killer (NK) cells and K562 cells, monocytes (MO) and/or interleukin (IL)-2/phytohemagglutinin (PHA) were administered. After MO were administered, reactive oxygen metabolites (ROM)/reactive nitrogen metabolites (RNM) productions increased, while tumor necrosis factor (TNF)-β/interferon (IFN)-γ levels and NK cell cytotoxicity (NCC) decreased, the changes of which after administering tiopronin (TIP) or glutamylcysteinylglycine (GSH) were opposite. In conclusions, the activated MO could inhibit the NK cell activity to kill K562 cell by secreting ROM and RNM. And TIP and GSH could scavenge both ROM and RNM to reverse the inhibitory effect of MO.

Post-consolidation immunotherapy with histamine dihydrochloride and interleukin-2 in AML

The initial chemotherapy in acute myeloid leukaemia (AML) comprises a first phase of induction and a second phase of consolidation. In the majority of patients, the induction treatment leads to complete remission (CR), defined as microscopic disappearance of leukaemic disease along with the return of normal haematopoiesis. However, despite the introduction of more efficacious consolidation regimens, a worryingly large proportion of AML patients in CR will subsequently experience relapses with poor prospects of long-term survival. A relapse is assumed to be the result of expansion of residual leukaemic cells that have escaped the initial chemotherapy. The anti-leukaemic functions of T cells and natural killer (NK) cells has formed the background to the use of interleukin-2 (IL-2), a T- and NK cell-activating cytokine, with the aim to eliminate residual leukaemia and hence reduce the relapse rate in AML, but the clinical trials using IL-2 monotherapy have yielded disappointment. A recent phase III study has demonstrated that post-consolidation treatment with the combination of histamine dihydrochloride (HDC) and IL-2 significantly prevents relapse in AML patients. Here we account for the preclinical background to the use of HDC/IL-2 in AML along with a review of clinical results.

Two randomised phase II trials of subcutaneous interleukin-2 and histamine dihydrochloride in patients with metastatic renal cell carcinoma

Histamine inhibits formation and release of phagocyte-derived reactive oxygen species, and thereby protects natural killer and T cells against oxidative damage. Thus, the addition of histamine may potentially improve the efficacy of interleukin-2 (IL-2). Two randomised phase II trials of IL-2 with or without histamine dihydrochloride (HDC) in patients with metastatic renal cell carcinoma (mRCC) were run in parallel. A total of 41 patients were included in Manchester, UK and 63 in Aarhus, Denmark. The self-administered, outpatient regimen included IL-2 as a fixed dose, 18 MIU s.c. once daily, 5 days per week for 3 weeks followed by 2 weeks rest. Histamine dihydrochloride was added twice daily, 1.0 mg s.c., concomitantly with IL-2. A maximum of four cycles were given. The Danish study showed a statistically significant 1-year survival benefit (76 vs 47%, P=0.03), a trend towards benefit in both median survival (18.3 vs 11.4 months, P=0.07), time to PD (4.5 vs 2.2 months, P=0.13) and clinical benefit (CR+PR+SD) (58 vs 37%, P=0.10) in favour of IL-2/HDC, whereas the UK study was negative for all end points. Only three patients had grade 4 toxicity; however, two were fatal. A randomised phase III trial is warranted to clarify the potential role of adding histamine to IL-2 in mRCC.

Histamine improves survival and protects against interleukin-2-induced pulmonary vascular leak syndrome in mice

The therapeutic efficacy in the treatment of metastatic cancer with high doses of interleukin-2 (IL-2) has been limited by the onset of vascular leak syndrome (VLS) and related toxicities. VLS is characterized by an increase in vascular permeability and severe hypotension resulting in interstitial edema and organ failure. This study explores the protective effects of histamine dihydrochloride (HDC) against IL-2-induced toxicities in mice. Treatment with HDC administered before or after IL-2 (1.25 x 10(6) IU, BID) was shown to protect mice from VLS-related toxicities and mortality in a dose-dependent manner. Survival rates when HDC was added were 56, 75 and 81% at doses of 0.47, 4.7 and 47.0 mg/kg, respectively, compared to 42% survival with IL-2 alone. HDC protected against IL-2-induced macroscopic pulmonary lesions, reduced edema (up to 62% reduction in lung wet/dry weight ratio) and reduced capillary leakage into the lungs as measured by a reduction in Evans Blue dye content. In addition, the systemic effect on serum cytokine levels showed that HDC only moderately lowered IL-2 induced IFN-gamma, IL-6, IL-10, IL-18 and TNF-alpha. Serum levels of IL-1beta, IL-4 and IL-12 were not measurably induced by IL-2 treatment. HDC modulates many cellular functions including regulating cytokines and blocking immune-suppression caused by reactive oxygen species (ROS) generated by the NADPH oxidase. However, the protective effect of HDC on alleviating IL-2-induced pulmonary edema was not related to ROS inhibition. Our data indicate that HDC treatment improves survival and protects against IL-2 induced VLS independent of ROS regulation in mice.

In vivo assessment of the antiproliferative properties of interferon-alpha during immunotherapy: Ki-67 (MIB-1) in patients with metastatic renal cell carcinoma

The aim of the present study was to investigate the in vivo antiproliferative effect of interferon alpha (IFN-α) in patients with metastatic renal cell carcinoma (mRCC). Core needle biopsies of metastatic and/or the primary kidney cancer were obtained before interleukin-2 (IL-2)- and IFN-α-based immunotherapy in 34 patients and repeated after 5 weeks in 25 patients. Tumour proliferation was assessed by use of the anti-Ki-67 antibody MIB-1 and evaluated in multiple, random systematic sampled fields of vision. Ki-67 labelling index (LI) at baseline was median 13.6% (range 1.2–85.0) and median 10.6% (range 1.3–48.6%) at week 5 with a median overall decline of 15.2% (range −95 to +258%) from baseline to week 5. There was no difference between responding and nonresponding patients. Ki-67 LI at week 5 was significantly correlated to survival. Thus, median survival of patients with Ki-67 LI ⩽10.6% at week 5 was 25.1 months compared to 11.5 months for patients with Ki-67 LI >10.6% (P=0.016). Baseline or change in Ki-67 LI did not correlate to survival. These data suggest that IFN-α in vivo has only modest effect on tumour proliferation in patients with mRCC. Tumour Ki-67 (MIB-1) reactivity after 1 month of immunotherapy appears to be a significant predictor of patient survival.

Immunotherapy as part of combinations for the treatment of cancer

Immunotherapy (biological therapy) comprises such things as active specific immunotherapy ("cancer vaccines"), nonspecific immunostimulation with cytokines, and the inhibition of suppressor influences exerted or elicited by the tumor. Just as cancer chemotherapy began with the use of single agents and evolved into combination therapy, so immunotherapeutic agents have been combined with each other and with chemotherapy. The alkylating agent cyclophosphamide (Cytoxan; CY) has been used for many years to inhibit tumor-derived suppressor influences in rodents, and has been exploited for the same use in humans. Combinations of CY and cancer vaccines such as autologous tumor cells, Melacine, large multivalent immunogen (LMI), and Theratope have been tested with some success in humans for more than a decade. In this use, the CY is a biological response modifier rather than an antitumor agent. Delayed treatment with CY in treating mouse plasmacytomas has proved more effective than immediate treatment, probably because it allows immunity to develop in the host. CY and moderate-dose interleukin-2 (IL-2) have also been a useful regimen in treating human melanomas. IL-2 is itself a useful component of combination immunotherapy, such as with melanoma peptide vaccines, or with interferon-alfa-2b, (IFN-a), as a dual combination or part of a biochemotherapy regimen. IL-2 and histamine, to block reactive oxygen species, may be a more useful combination for treatment of liver metastases of melanoma than IL-2 alone. In this combination, the histamine may permit continued, unimpeded activity of cytolytic T lymphocytes. Several different combinations of drugs and biological agents have been used as biochemotherapy for melanoma, but although there are higher immediate response rates, the long-range survival benefits have been marginal, not justifying the severe toxicity. Combinations of 5-fluorouracil (5-FU) and IFN-a or levamisole have had efficacy in colon and head and neck cancers, but here the biological agents acted as biochemical modulators. Trials of antibodies and chemotherapy have been limited. It appears that trastuzumab (Herceptin) potentiates antitumor therapy in breast cancer and also increases the cardiotoxicity of those regimens.

Toxicology and toxicokinetics of acute and subchronic administration of histamine dihydrochloride in rats

Histamine dihydrochloride is currently being evaluated as an adjuvant to immunotherapy regimens in neoplastic and infectious diseases. The no-observed-effect-level (NOEL), no-observable-adverse-effect-level (NOAEL), and pharmacokinetics of subcutaneously administered histamine dihydrochloride were determined via 5 and 28 day repeated dose studies in Sprague-Dawley rats. In the five day study, male rats received 0 (vehicle), 5, 30, 500, or 1000 mg/kg BID. Acute tissue damage was observed at one or more injection sites in the two highest dose groups after 24 h. At five days, animals in these groups displayed indications of pathological inflammation at the injection sites. In the 28 day study, male and female rats received 0 (vehicle), 0.5, 5, or 100 mg/kg BID. The most significant treatment-related pathological findings were signs of inflammation at the injection sites for animals in the 100 mg/kg BID group. Hematology and clinical chemistry changes in the highest dose groups in both studies were consistent with inflammation and anemia but were found to be reversible following a 14-day recovery. Plasma histamine levels were quantified from male and female animals receiving 0.5, 5, and 100 mg/kg injections on Day 1 and 28 of the twenty-eight day study. Cmax was achieved within 0.25 h and was dose-proportional. The elimination half-life and tmax were longer at the 100 mg/kg dose than the lower doses. No marked differences between genders or between Day 1 and 28 were found. Based on these findings, the NOEL and NOAEL were established at 0.5 mg/kg BID and 5 mg/kg BID, respectively. When converted to human equivalent dose, the NOAEL is 0.81 mg/kg which is 54 times the intended human dose. These studies support a wide safety margin for histamine dihydrochloride.

A multicentre, randomized study to evaluate the safety and efficacy of histamine dihydrochloride and interferon-alpha-2b for the treatment of chronic hepatitis C

Interferon- (IFN-)alpha is currently the standard of care treatment for patients with chronic hepatitis C virus (HCV) infection. A significant part of the benefit of IFN-alpha in chronic hepatitis C is believed to be related to the activation of lymphocytes such as T cells and natural killer (NK) cells, which participate in the elimination of infected cells. Histamine dihydrochloride (HDC) has been shown to potentiate the IFN-alpha-induced activation of T cells and NK cells by a mechanism that involves the protection of these lymphocytes against oxygen radical-induced functional inhibition and apoptosis. This study was designed to examine the efficacy and safety of HDC in combination with IFN-alpha-2b in treatment-naïve patients with chronic HCV infection. All patients received IFN-alpha-2b, 3 MIU, three times weekly via subcutaneous injection, and were randomized to one of four HDC regimens (1 mg of either: once a day, three times a week; once a day, five times a week; twice a day, three times a week or; twice a day, five times a week). The doses of HDC in combination with IFN-alpha-2b resulted in sustained viral response rates ranging from 31% to 38%. Sustained biochemical response rates ranged from 28% to 41% across the four treatment groups. Patients infected with HCV genotype 1, and those with high baseline viral levels, which are characteristics associated with poor prognosis, had sustained virologic response rates ranging from 18% to 42% and 15% to 39%, respectively. Combination treatment was generally well tolerated. We propose that the potential benefit of HDC + IFN therapy for chronic HCV infection should be the focus of further investigation.

Pharmacokinetics of histamine dihydrochloride in healthy volunteers and cancer patients: implications for combined immunotherapy with interleukin-2

Recent clinical trials in melanoma and leukemia have demonstrated potential for increased survival time and improved remission when histamine dihydrochloride is added to cytokine monotherapy. In the present study, the pharmacokinetics of subcutaneous histamine (1 mg) in 21 healthy subjects and 12 melanoma patients was determined via model-dependent methods. Drug-drug interactions with subcutaneous interleukin-2 (1.1 mg) were evaluated in a combined cohort of patients with melanoma (n = 8) or renal cell carcinoma (n = 4). Histamine dihydrochloride administered over 10 minutes in healthy subjects peaked at 18 minutes (Cmax 38 nmol/L), attained a distribution volume of 59 L, and was eliminated at 6%/min. The results were similar in a 20-minute infusion in melanoma patients. No gender effects were observed (p > 0.05). Interleukin-2 injected either 10 minutes prior to or 10 minutes following histamine dihydrochloride had no effect on histamine kinetics. Histamine dihydrochloride administered 10 minutes prior to injection of interleukin-2 also had no effect on interleukin-2 kinetics. Maximal concentration of interleukin-2 (2,442 pg/ml) occurred at 2.5 hours with an elimination half-life of 1.7 hours, area under the curve (AUC) of 15,746 pg x h/ml, and volume of distribution and plasma clearance of 194 L and 74 L/h, respectively. However, interleukin-2 Cmax (1,758 pg/ml) and AUC (12,448 pg x h/ml) were reduced when histamine dihydrochloride was infused 10 minutes following interleukin-2, likely due to the pharmacodynamic effects of histamine, including increased heart rate and reduced blood pressure. It is concluded that histamine dihydrochloride and interleukin-2 can be safely coadministered with minimal interaction.