Immune recovery after cyclophosphamide treatment in multiple myeloma: implication for maintenance immunotherapy

Abscopal Effect and Drug-Induced Xenogenization: A Strategic Alliance in Cancer Treatment?

The current state of cancer treatment is still far from being satisfactory considering the strong impairment of patients' quality of life and the high lethality of malignant diseases. Therefore, it is critical for innovative approaches to be tested in the near future. In view of the crucial role that is played by tumor immunity, the present review provides essential information on the immune-mediated effects potentially generated by the interplay between ionizing radiation and cytotoxic antitumor agents when interacting with target malignant cells. Therefore, the radiation-dependent abscopal effect (i.e., a biological effect of ionizing radiation that occurs outside the irradiated field), the influence of cancer chemotherapy on the antigenic pattern of target neoplastic cells, and the immunogenic cell death (ICD) caused by anticancer agents are the main topics of this presentation. It is widely accepted that tumor immunity plays a fundamental role in generating an abscopal effect and that anticancer drugs can profoundly influence not only the host immune responses, but also the immunogenic pattern of malignant cells. Remarkably, several anticancer drugs impact both the abscopal effect and ICD. In addition, certain classes of anticancer agents are able to amplify already expressed tumor-associated antigens (TAA). More importantly, other drugs, especially triazenes, induce the appearance of new tumor neoantigens (TNA), a phenomenon that we termed drug-induced xenogenization (DIX). The adoption of the abscopal effect is proposed as a potential therapeutic modality when properly applied concomitantly with drug-induced increase in tumor cell immunogenicity and ICD. Although little to no preclinical or clinical studies are presently available on this subject, we discuss this issue in terms of potential mechanisms and therapeutic benefits. Upcoming investigations are aimed at evaluating how chemical anticancer drugs, radiation, and immunotherapies are interacting and cooperate in evoking the abscopal effect, tumor xenogenization and ICD, paving the way for new and possibly successful approaches in cancer therapy.

T-Regulatory Cells In Tumor Progression And Therapy

Regulatory T cells (Tregs) are important members of the immune system regulating the host responses to infection and neoplasms. Tregs prevent autoimmune disorders by protecting the host-cells from an immune response, related to the peripheral tolerance. However, tumor cells use Tregs as a shield to protect themselves against anti-tumor immune response. Thus, Tregs are a hurdle in achieving the complete potential of anti-cancer therapies including immunotherapy. This has prompted the development of novel adjuvant therapies that obviate their negative effects thereby enhancing the therapeutic efficacy. Our earlier studies have shown the efficacy of the glycolytic inhibitor, 2-deoxy-D-glucose (2-DG) by reducing the induced Tregs pool and enhance immune stimulation as well as local tumor control. These findings have suggested its potential for enhancing the efficacy of immunotherapy, besides radiotherapy and chemotherapy. This review provides a brief account of the current status of Tregs as a component of the immune-biology of tumors and various preclinical and clinical strategies pursued to obviate the limitations imposed by them in achieving therapeutic efficacy.

Antitumor Synergism and Enhanced Survival with a Tumor Vasculature-Targeted Enzyme Prodrug System, Rapamycin, and Cyclophosphamide

Mutant cystathionine gamma-lyase was targeted to phosphatidylserine exposed on tumor vasculature through fusion with Annexin A1 or Annexin A5. Cystathionine gamma-lyase E58N, R118L, and E338N mutations impart nonnative methionine gamma-lyase activity, resulting in tumor-localized generation of highly toxic methylselenol upon systemic administration of nontoxic selenomethionine. The described therapeutic system circumvents systemic toxicity issues using a novel drug delivery/generation approach and avoids the administration of nonnative proteins and/or DNA required with other enzyme prodrug systems. The enzyme fusion exhibits strong and stable in vitro binding with dissociation constants in the nanomolar range for both human and mouse breast cancer cells and in a cell model of tumor vascular endothelium. Daily administration of the therapy suppressed growth of highly aggressive triple-negative murine 4T1 mammary tumors in immunocompetent BALB/cJ mice and MDA-MB-231 tumors in SCID mice. Treatment did not result in the occurrence of negative side effects or the elicitation of neutralizing antibodies. On the basis of the vasculature-targeted nature of the therapy, combinations with rapamycin and cyclophosphamide were evaluated. Rapamycin, an mTOR inhibitor, reduces the prosurvival signaling of cells in a hypoxic environment potentially exacerbated by a vasculature-targeted therapy. IHC revealed, unsurprisingly, a significant hypoxic response (increase in hypoxia-inducible factor 1 α subunit, HIF1A) in the enzyme prodrug-treated tumors and a dramatic reduction of HIF1A upon rapamycin treatment. Cyclophosphamide, an immunomodulator at low doses, was combined with the enzyme prodrug therapy and rapamycin; this combination synergistically reduced tumor volumes, inhibited metastatic progression, and enhanced survival. Mol Cancer Ther; 16(9); 1855-65. ©2017 AACR.

In vivo amelioration of endogenous antitumor autoantibodies via low-dose P4N through the LTA4H/activin A/BAFF pathway

Cancer progression is associated with the development of antitumor autoantibodies in patients' sera. Although passive treatment with antitumor antibodies has exhibited remarkable therapeutic efficacy, inhibitory effects on tumor progression by endogenous antitumor autoantibodies (EAAs) have been limited. In this study, we show that P₄N, a derivative of the plant lignan nordihydroguaiaretic acid (NDGA), enhanced the production of EAAs and inhibited tumor growth at low noncytotoxic concentrations via its immunoregulatory activity. Intratumoral injection of P₄N improved the quantity and quality of EAAs, and passive transfer of P₄N-induced EAAs dramatically suppressed lung metastasis formation and prolonged the survival of mice inoculated with metastatic CT26 tumor cells. P₄N-induced EAAs specifically recognized two surface antigens, 78-kDa glucose-regulated protein (GRP78) and F1F0 ATP synthase, on the plasma membrane of cancer cells. Additionally, P₄N treatment led to B-cell proliferation, differentiation to plasma cells, and high titers of autoantibody production. By serial induction of autocrine and paracrine signals in monocytes, P₄N increased B-cell proliferation and antibody production via the leukotriene A4 hydrolase (LTA4H)/activin A/B-cell activating factor (BAFF) pathway. This mechanism provides a useful platform for studying and seeking a novel immunomodulator that can be applied in targeting therapy by improving the quantity and quality of the EAAs.

Mobilization with cyclophosphamide reduces the number of lymphocyte subpopulations in the leukapheresis product and delays their reconstitution after autologous hematopoietic stem cell transplantation in patients with multiple myeloma

BACKGROUND

Autologous hematopoietic stem cell transplantation is considered the standard of care for younger patients with multiple myeloma. Several mobilization regimens are currently used, most commonly growth factors alone or in combination with chemotherapy. The aim of our study was to investigate the differences in lymphocyte subpopulation counts between three different mobilization regimens on collection day, in the leukapheresis product and on day 15 after autologous hematopoietic stem cell transplantation.

PATIENTS AND METHODS

In total 48 patients were prospectively enrolled in three different mobilization regimens; (i) filgrastim (20), (ii) pegfilgrastim (19) and (iii) cyclophosphamide + filgrastim (9). Lymphocytes, CD16+/56+ natural killer and CD4+/CD25^high T regulatory cells were determined by flow cytometry.

RESULTS

We found a statistically significant difference between the mobilization regimens. Cyclophosphamide reduced lymphocyte and natural killer (NK) cell counts on collection day (lymphocytes 1.08 × 10⁹/L; NK cells 0.07 × 10⁹/L) compared to filgrastim (lymphocytes 3.08 × 10⁹/L; NK cells 0.52 × 10⁹/L) and pegfilgrastim (lymphocytes 3 × 10⁹/L; NK cells 0.42 × 10⁹/L). As a consequence lymphocyte and NK cell counts were also lower in the leukapheresis products following cyclophosphamide mobilization regimen (lymphocytes 50.1 × 10⁹/L; NK cells 4.18 × 10⁹/L) compared to filgrastim (lymphocytes 112 × 10⁹/L; NK cells 17.5 × 10⁹/L) and pegfilgrastim (lymphocytes 112 × 10⁹/L; NK cells 14.3 × 10⁹/L). In all mobilization regimens T regulatory cells increased 2-fold on collection day, regarding the base line value before mobilization. There was no difference in T regulatory cell counts between the regimens.

CONCLUSIONS

Mobilization with cyclophophamide reduces the number of mobilized and collected lymphocytes and NK cells as compared to mobilization with growth factors only and results in their delayed reconstitution following autologous hematopoietic stem cell transplantation. We found no difference between filgrastim and pegfilgrastim mobilization.

Increase of peripheral T regulatory cells during remission induction with cyclophosphamide in active systemic lupus erythematosus

BACKGROUND

Cyclophosphamide efficacy in lupus nephritis (LN) and neuropsychiatric systemic lupus erythematosus (NPSLE) is probably mediated by a non-specific ablation of reactive lymphocytes. However, little is known in regard to its effect on T regulatory cells (Tregs) in such patients, which was the aim of this study.

PATIENTS AND METHODS

Ten Caucasian lupus patients were included, six with LN classes IV-V (mean age 33.8 ± 8.8 years) and four with NPSLE (mean age 35.5 ± 8.8 years, clinical manifestations: 1/4 acute confusional state, 1/4 psychosis, 2/4 refractory seizures). Cyclophosphamide was administered at monthly pulses (500 mg/m(2) /month for 6 months); doses of other administered drugs, including steroids, remained stable or lower. CD4(+) CD25(high) FOXP3(+) Tregs were assessed by flow-cytometry at baseline and before every subsequent pulse and 3-6 months after the final pulse. Disease activity was assessed by SLE Disease Activity Index (SLEDAI).

RESULTS

In LN patients, Tregs were significantly increased even after the fourth pulse (0.54 ± 0.20% vs. 1.24 ± 0.29%, P < 0.001). Likewise, in NPSLE, Tregs were significantly expanded after the fourth pulse (0.57 ± 0.23% vs. 1.41 ± 0.28%, P < 0.001). SLEDAI was significantly reduced in all patients.

CONCLUSIONS

Cyclophosphamide pulse therapy was associated with a significant increase of the CD4(+) CD25(high) FOXP3(+) Tregs in patients with active LN and NPSLE. This effect is probably indirect and may partially explain the beneficial role of cyclophosphamide in such cases.

Human CD4+CD25+ regulatory T cells are sensitive to low dose cyclophosphamide: implications for the immune response

Regulatory T cells (Treg) play a pivotal role in the immune system since they inhibit the T cell response. It is well known that cyclophosphamide applied at low dose is able to stimulate the immune response while high dose cyclophosphamide exerts inhibitory activity. Data obtained in mice indicate that cyclophosphamide provokes a reduction in the number of Treg and impairs their suppressive activity, resulting in immune stimulation. Here, we addressed the question of the sensitivity of human Treg to cyclophosphamide, comparing Treg with cytotoxic T cells (CTL) and T helper cells (Th). We show that Treg are more sensitive than CTL and Th to mafosfamide, which is an active derivative of cyclophosphamide, which does not need metabolic activation. The high sensitivity of Treg was due to the induction of apoptosis. Treg compared to CTL and Th were not more sensitive to the alkylating drugs temozolomide and nimustine and also not to mitomycin C, indicating a specific Treg response to mafosfamide. The high sensitivity of Treg to mafosfamide resulted not only in enhanced cell death, but also in impaired Treg function as demonstrated by a decline in the suppressor activity of Treg in a co-culture model with Th and Helios positive Treg. Treatment of Treg with mafosfamide gave rise to a high level of DNA crosslinks, which were not repaired to the same extent as observed in Th and CTL. Also, Treg showed a low level of γH2AX foci up to 6 h and a high level 24 h after treatment, indicating alterations in the DNA damage response. Overall, this is the first demonstration that human Treg are, in comparison with Th and CTL, hypersensitive to cyclophosphamide, which is presumably due to a DNA repair defect.

Targeting single-walled carbon nanotubes for the treatment of breast cancer using photothermal therapy

This paper focuses on the targeting of single-walled carbon nanotubes (SWNTs) for the treatment of breast cancer with minimal side effects using photothermal therapy. The human protein annexin V (AV) binds specifically to anionic phospholipids expressed externally on the surface of tumour cells and endothelial cells that line the tumour vasculature. A 2 h incubation of the SWNT-AV conjugate with proliferating endothelial cells followed by washing and near-infrared (NIR) irradiation at a wavelength of 980 nm was enough to induce significant cell death; there was no significant cell death with irradiation or the conjugate alone. Administration of the same conjugate i.v. in BALB/c female mice with implanted 4T1 murine mammary at a dose of 0.8 mg SWNT kg(-1) and followed one day later by NIR irradiation of the tumour at a wavelength of 980 nm led to complete disappearance of implanted 4T1 mouse mammary tumours for the majority of the animals by 11 days since the irradiation. The combination of the photothermal therapy with the immunoadjuvant cyclophosphamide resulted in increased survival. The in vivo results suggest the SWNT-AV/NIR treatment is a promising approach to treat breast cancer.

Efficacy of stem cell mobilization in patients with newly diagnosed multiple myeloma after a CTD (cyclophosphamide, thalidomide, and dexamethasone) regimen

The CTD (cyclophosphamide, thalidomide, and dexamethasone) regimen is known to be an effective primary therapy in patients with newly diagnosed multiple myeloma (MM). However, stem cell yields after CTD remain inconsistent. The aim of the present study is to identify the influence of the CTD regimen on the outcome of peripheral blood stem cell (PBSC) collection. Fifty-four patients received four cycles of CTD, and PBSCs were mobilized with cyclophosphamide and G-CSF or with G-CSF alone. Each patient from whom ≤4.0 × 10(6) CD34(+) cells/kg were collected received a second mobilization course. The median duration from the start of a CTD regimen to the first collection was 4.3 months. Forty-eight patients were mobilized with cyclophosphamide followed by G-CSF, and six patients were mobilized with G-CSF alone. The median day of apheresis was day 3 (range day 2-day 5). The overall response rate at mobilization was 96.3 %, including 11.1 % complete response, 22.2 % very good partial response, and 63.0 % partial response. The median number of harvested CD34(+) cells was 12.8 × 10(6) cells/kg. At the second mobilization, 88.9 % of patients reached the minimal stem cell collection target of ≥2.0 × 10(6) cells/kg, and 75.9 % of patients achieved the collection target of ≥4.0 × 10(6) cells/kg. CTD within four cycles is an effective primary therapy in patients with newly diagnosed MM and only minimally affects subsequent PBSC collection.