An integrated disease/pharmacokinetic/pharmacodynamic model suggests improved interleukin-21 regimens validated prospectively for mouse solid cancers

Interleukin (IL)-21 is an attractive antitumor agent with potent immunomodulatory functions. Yet thus far, the cytokine has yielded only partial responses in solid cancer patients, and conditions for beneficial IL-21 immunotherapy remain elusive. The current work aims to identify clinically-relevant IL-21 regimens with enhanced efficacy, based on mathematical modeling of long-term antitumor responses. For this purpose, pharmacokinetic (PK) and pharmacodynamic (PD) data were acquired from a preclinical study applying systemic IL-21 therapy in murine solid cancers. We developed an integrated disease/PK/PD model for the IL-21 anticancer response, and calibrated it using selected "training" data. The accuracy of the model was verified retrospectively under diverse IL-21 treatment settings, by comparing its predictions to independent "validation" data in melanoma and renal cell carcinoma-challenged mice (R(2)>0.90). Simulations of the verified model surfaced important therapeutic insights: (1) Fractionating the standard daily regimen (50 μg/dose) into a twice daily schedule (25 μg/dose) is advantageous, yielding a significantly lower tumor mass (45% decrease); (2) A low-dose (12 μg/day) regimen exerts a response similar to that obtained under the 50 μg/day treatment, suggestive of an equally efficacious dose with potentially reduced toxicity. Subsequent experiments in melanoma-bearing mice corroborated both of these predictions with high precision (R(2)>0.89), thus validating the model also prospectively in vivo. Thus, the confirmed PK/PD model rationalizes IL-21 therapy, and pinpoints improved clinically-feasible treatment schedules. Our analysis demonstrates the value of employing mathematical modeling and in silico-guided design of solid tumor immunotherapy in the clinic.     

New insights into IL-12-mediated tumor suppression

During the past two decades, interleukin-12 (IL-12) has emerged as one of the most potent cytokines in mediating antitumor activity in a variety of preclinical models. Through pleiotropic effects on different immune cells that form the tumor microenvironment, IL-12 establishes a link between innate and adaptive immunity that involves different immune effector cells and cytokines depending on the type of tumor or the affected tissue. The robust antitumor response exerted by IL-12, however, has not yet been successfully translated into the clinics. The majority of clinical trials involving treatment with IL-12 failed to show sustained antitumor responses and were associated to toxic side effects. Here we discuss the therapeutic effects of IL-12 from preclinical to clinical studies, and will highlight promising strategies to take advantage of the antitumor activity of IL-12 while limiting adverse effects.     

Antitumor activity of Herceptin in combination with STEALTH liposomal cisplatin or nonliposomal cisplatin in a HER2 positive human breast cancer model

Single agent antitumor activity of Herceptin, a humanized monoclonal antibody directed against HER2, has been demonstrated in numerous preclinical and clinical studies. Additionally, combination therapy with Herceptin and chemotherapy (CRx) has demonstrated additive antitumor activity in both preclinical models and early clinical trials. STEALTH (pegylated) liposomal (PL) cisplatin, also known as SPI-077, is currently in clinical trials for a variety of solid tumors. The three studies reported here discuss the antitumor activity of the combination of Herceptin and nonliposomal cisplatin or PL-cisplatin in two xenograft tumor models, initiated from the cell lines, BT474 and MDA453, that overexpress the oncogene, HER2. Herceptin alone had significant antitumor activity in all three experiments (p < 0.0001). Nonliposomal cisplatin and PL-cisplatin were both effective antitumor agents but, at tolerable dose levels, PL-cisplatin was superior to nonliposomal cisplatin (p < 0.0003). The effect of combining Herceptin with the chemotherapeutic cisplatin or PL-cisplatin, was most significant at moderate doses of H (0.5 mg/kg, p < 0.0001), but tended to be greater than either agent alone in all experiments. The combination of PL-cisplatin with Herceptin had statistically similar antitumor activity to that of nonliposomal cisplatin with Herceptin in all experiments. We conclude that combination therapy with PL-cisplatin and Herceptin results in significant antitumor activity with the potential for reducing toxicity in metastatic breast cancer patients.     

IL-17E, a proinflammatory cytokine, has antitumor efficacy against several tumor types in vivo

Interleukin-17E (IL-17E) belongs to a novel family of cytokines that possess significant homology to IL-17. IL-17E has potent inflammatory effects in vitro and in vivo. Overexpression of IL-17E in mice results in a T helper-2 (Th2)-type immune response, which includes the expansion of eosinophils through the production of IL-5, and elevated gene expression of IL-4 and IL-13 in multiple tissues. In this study, we show that IL-17E has antitumor activity in vivo, a previously unrecognized function of IL-17E. Antitumor efficacy of IL-17E was examined in a variety of human tumor xenograft models, including melanoma, breast, lung, colon, and pancreatic cancers. Injection of recombinant IL-17E every other day resulted in significant antitumor activity in these tumor models. In addition, the combination of IL-17E with chemotherapy or immunotherapy agents showed an enhanced antitumor efficacy in human tumor xenograft models in mice as compared to either agent alone. Antitumor activity was demonstrated using different routes of administration, including intraperitoneal, intravenous, and subcutaneous injection. Anticancer activity was shown for both mouse and human forms of IL-17E, which have a high degree of sequence identity. Tumor-bearing mice treated with IL-17E showed a significant increase in serum levels of IL-5 and increased numbers of eosinophils in peripheral blood compared to the control group. Spleens isolated from IL-17E-treated mice showed a significant increase in eosinophils that correlated with antitumor activity of IL-17E in a dose–response manner. Finally, we demonstrate that B cells are necessary for IL-17E-mediated antitumor activity and that IL-17E was found to activate signaling pathways in B cells in vitro. Taken together, these data demonstrate that IL-17E has antitumor activity in vivo, and support further investigation of the potential clinical use of IL-17E as an anticancer agent.     

Modulation of cisPlatin cytotoxicity by interleukin-1α and resident tumor macrophages

The modulation of cisPlatin cytotoxicity by interleukin-1 (IL-1α) was studied in cultures of SCC-7 tumor cells with and without tumor macrophages to examine potential mechanisms for the synergistic antitumor activity of cisPlatin and IL-1α in SCC-7 solid tumors. Neither IL-1α nor tumor macrophages affected the survival of clonogenic tumor cells and IL-1α had no direct effect on tumor cell growthin vitro. Macrophages had no direct effect on cisPlatin sensitivity (IC₉₀=6.0 μM), but, the addition of IL-1α (500–2000U/ml) to co-cultures of cisPlatin pretreated tumor cells and resident tumor macrophages increased cell killing (IC₉₀=3.1 μM). Similar responses were seen in primary cultures treated with cisPlatin before IL-1α. The modulation of cisPlatin cytotoxicity by IL-1α exhibited a biphasic dose response that paralleled the IL-1α dose dependent release of H₂O₂by resident tumor macrophages. Further, IL-1α modification of cisPlatin cytotoxicity was prompt and inhibited by catalase. CisPlatin and exogenous H₂O₂ (50 μM) produced more than additive SCC-7 clonogenic cell kill and hydroxyl radicals played an important role in the response. Interleukin-1 modulation of cisPlatin cytotoxicity was schedule dependent. IL-1α treatment for 24 hrs, before cisPlatin, produced drug resistance (IC₉₀=11.1 μM). Our study shows that IL-1α can stimulate tumor macrophages to release pro-oxidants that modify cellular chemosensitivity in a schedule and dose dependent fashion. Our findings may also provide a mechanistic explanation for the synergistic antitumor activity of cisPlatin and IL-1αin vivo.     

白细胞介素-2联合环磷酰胺对乳腺癌荷瘤小鼠调节性T细胞的影响

目的：调节性T细胞（Regulatory T cells,Treg）被认为能够抑制抗肿瘤免疫反应,从而促进肿瘤生长。环磷酰胺（Cyclophosphamide,CTX）是个常规化疗药物,现在更多的注意力集中在其小剂量应用时可以删除Treg。了解小剂量环磷酰胺联合白细胞介素-2（Interleukin-2,IL-2）对4T1Balb/c乳腺癌荷瘤小鼠调节性T细胞的影响及其抗肿瘤效果。方法：通过皮下接种4T1乳腺癌细胞建立乳腺癌Balb/c荷瘤小鼠模型;20只荷瘤小鼠随机分为IL-2＋NS组、PBS＋CTX组、IL-2＋CTX组及PBS＋NS组,在种瘤第10天开始对荷瘤小鼠分别经腹腔按方案给药。在种瘤后第16天人道处死小鼠,采用流式细胞术检测小鼠脾脏中CD4＋CD25＋调节性T细胞数量,应用ELISA法检测血清干扰素-γ浓度,电子称称量肿瘤重量。结果：与对照组相比,在应用IL-2后,荷瘤小鼠脾脏CD4＋CD25＋/CD4＋比值增加,在应用IL-2的同时使用小剂量CTX可减少CD4＋CD25＋/CD4＋的比值;单次及联合用药均可提高血清INF-γ浓度;联合用药可减少肿瘤重量。结论：小剂量CTX可以减少由使用IL-2所增加的Treg数量,促进抗肿瘤免疫,提高IL-2的抗瘤效果,从而抑制肿瘤生长。该研究可能为乳腺癌的临床治疗提供一种有效的方法。     

Priming of the antitumor response promotes efficacy of interleukin-2 therapy

 We have studied the effect of active specific immunization (ASI) on the antitumor response induced by locoregional, low-dose interleukin-2 (IL-2) therapy. On day 0, mice were injected i.p. with viable, syngeneic tumor cells and with irradiated tumor cells (ASI). Low-dose IL-2 treatment was given i.p. for 5 consecutive days. ASI led to extended survival in two out of seven models tested. In these two models, enhanced efficacy was observed when both ASI and IL-2 were administered. In the five models in which ASI had no therapeutic value, ASI+IL-2 treatment was no more effective than IL-2 therapy. In the SL2 lymphoma model, use of ASI prior to IL-2 therapy given as early as days 1–5 led to at least 60% cure, whereas IL-2 therapy without ASI was only effective when administered after day 9. In the P815 mastocytoma model, however, ASI, IL-2, and the combination caused negative (suppressive) effects when administered on days 6–10. IL-2 administered on days 6–10 was therapeutically effective in this model when mice were treated with cyclophosphamide on day 6. In both the SL2 and the P815 tumor models, cured mice were specifically immune. The positive and negative effects observed were not due to the increased number of cells injected (non-specific inflammation) nor to possible antigenic alteration of the ASI cells by irradiation, as ASI with fragmented tumor cells was also effective in inducing synergy. Investigations into the underlying mechanism indicated that CD4⁺ cells play an important role. In total, the results indicate that ASI may be a good supplement to locoregional IL-2 treatment if care is taken to alleviate immunosuppressive activities. Received: 6 February 1997 / Accepted: 6 March 1997     

Pre-existing tumor-sensitized T cells are essential for eradication of established tumors by IL-12 and cyclophosphamide plus IL-12.

The antitumor immune response activated by IL-12, especially by a combination of cyclophosphamide and IL-12 (Cy+IL-12), is clinically significant in certain experimental tumor models, in that a number of well-established (10-20 mm in diameter) s.c. tumors are completely eradicated. Furthermore, Cy+IL-12 treatment is also able to eradicate well-established grossly detectable experimental lung metastases and advanced ascites tumors. Despite the dramatic antitumor effects seen in some tumor models, Cy+IL-12 fails to induce regression of other established tumors. Characterization of tumor immunogenicity shows that all tumors responding to IL-12 and Cy+IL-12 treatments are immunogenic tumors, in that an antitumor immune response is detectable in tumor-bearing hosts upon tumor establishment. In contrast, none of the nonimmunogenic tumor responds to IL-12 and Cy+IL-12 treatments. Analysis of cellular requirements for successful tumor rejection through an adoptive cell transfer approach reveals that the presence of tumor-sensitized, but not naive, T cells is essential for tumor rejection by IL-12 and Cy+IL-12. Transfer of these tumor-sensitized T cells must be conducted before, but not after, IL-12 treatment in order for tumor rejection to occur. The requirement of sensitized T cells is also tumor specific. In mice bearing immunogenic tumors, the presence of pre-existing tumor-sensitized T cells is demonstrated by adoptive cell transfer experiments using purified spleen T cells from these mice. Results from our study show that Cy+IL-12-based immunotherapy of cancer may be highly effective and that pre-existing tumor-sensitized T cells are essential for the success of the therapy.     

In situ antitumor vaccination: Targeting the tumor microenvironment

Tumor microenvironment is known to play important roles in tumor progression. Many therapies, targeting the tumor microenvironment, are designed and applied in the clinic. One of these approaches is in situ antitumor therapy. This way, bacteria, antibodies, plasmid DNA, viruses, and cells are intratumorally delivered into the tumor site as “in-situ antitumor vaccine,” which seeks to enhance immunogenicity and generate systemic T cell responses. In addition, this intratumoral therapy can alter the tumor microenvironment from immunosuppressive to immunostimulatory while limiting the risk of systemic exposure and associated toxicity. Contemporarily, promising preclinical results and some initial success in clinical trials have been obtained after intratumoral therapy.     

Virulizin® induces production of IL-17E to enhance antitumor activity by recruitment of eosinophils into tumors

Virulizin has demonstrated strong antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. Our previous studies have demonstrated that macrophages, NK cells, and cytokines are important in the antitumor mechanism of Virulizin. Virulizin treatment of tumor bearing mice results in the expansion as well as increased activity of monocytes/macrophages and production of cytokines IL-12 and TNFalpha and activation of NK cells. In this study we show that the inflammatory cytokine IL-17E (IL-25) is induced by Virulizin treatment and is part of its antitumor mechanism. IL-17E is a proinflammatory cytokine, which induces a T(H)2 type immune response, associated with eosinophil expansion and infiltration into mucosal tissues. IL-17E was increased in sera of Virulizin-treated mice bearing human melanoma xenografts, compared to saline-treated controls, as shown by 2D gel electrophoresis and ELISA. Treatment of splenocytes in vitro with Virulizin resulted in increased IL-17E mRNA expression, which peaked between 24 and 32 h post-stimulation. Both in vitro and in vivo experiments demonstrated that B cells produced IL-17E in response to Virulizin treatment. Furthermore, Virulizin treatment in vivo resulted in increased blood eosinophilia and eosinophil infiltration into tumors. Finally, injection of recombinant IL-17E showed antitumor activity towards xenografted tumors, which correlated with increased eosinophilia in blood and tumors. Taken together, these results support another antitumor mechanism mediated by Virulizin, through induction of IL-17E by B cells, leading to recruitment of eosinophils into tumors, which may function in parallel with macrophages and NK cells in mediating tumor destruction.     

Potent antitumor effects of combination therapy with IFNs and monocytes in mouse models of established human ovarian and melanoma tumors

Interferon-activated monocytes are known to exert cytocidal activity against tumor cells in vitro. Here, we have examined whether a combination of IFN-α2a and IFN-γ and human monocytes mediate significant antitumor effects against human ovarian and melanoma tumor xenografts in mouse models. OVCAR-3 tumors were treated i.t. with monocytes alone, IFN-α2a and IFN-γ alone or combination of all three on day 0, 15 or 30 post-tumor implantation. Mice receiving combination therapy beginning day 15 showed significantly reduced tumor growth and prolonged survival including complete regression in 40% mice. Tumor volumes measured on day 80 in mice receiving combination therapy (206 mm(3)) were significantly smaller than those of mice receiving the IFNs alone (1,041 mm(3)), monocytes alone (1,111 mm(3)) or untreated controls (1,728 mm(3)). Similarly, combination therapy with monocytes and IFNs of much larger tumor also inhibited OVCAR-3 tumor growth. Immunohistochemistry studies showed a large number of activated macrophages (CD31(+)/CD68(+)) infiltrating into OVCAR-3 tumors and higher densities of IL-12, IP10 and NOS2, markers of M1 (classical) macrophages in tumors treated with combination therapy compared to the controls. Interestingly, IFNs-activated macrophages induced apoptosis of OVCAR-3 tumor cells as monocytes alone or IFNs alone did not mediate significant apoptosis. Similar antitumor activity was observed in the LOX melanoma mouse model, but not as profound as seen with the OVCAR-3 tumors. Administration of either mixture of monocytes and IFN-α2a or monocytes and IFN-γ did not inhibit Lox melanoma growth; however, a significant inhibition was observed when tumors were treated with a mixture of monocytes, IFN-α2a and IFN-γ. These results indicate that monocytes and both IFN-α2a and IFN-γ may be required to mediate profound antitumor effect against human ovarian and melanoma tumors in mouse models.     

NHS-IL12 and bintrafusp alfa combination therapy enhances antitumor activity in preclinical cancer models

Combinatorial immunotherapy approaches are emerging as viable cancer therapeutic strategies for improving patient responses and outcomes. This study investigated whether two such immunotherapies, with complementary mechanisms of action, could enhance antitumor activity in murine tumor models. The immunocytokine NHS-IL12, and surrogate NHS-muIL12, are designed to deliver IL-12 and muIL-12, respectively, to the tumor microenvironment (TME) to activate NK cells and CD8⁺ T cells and increase their cytotoxic functions. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domains of the TGF-β receptor II to function as a TGF-β “trap” fused to a human IgG1 antibody blocking PD-L1. With this dual-targeting strategy, BA enhances efficacy over that of monotherapies in preclinical studies. In this study, NHS-muIL12 and BA combination therapy enhanced antitumor activity, prolonged survival, and induced tumor-specific antitumor immunity. This combination therapy increased tumor-specific CD8⁺ T cells and induced immune profiles, consistent with the activation of both adaptive and innate immune systems. In addition, BA reduced lung metastasis in the 4T1 model. Collectively, these findings could support clinical trials designed to investigate NHS-IL12 and BA combination therapy for patients with advanced solid tumors     

Type I IFN contributes to NK cell homeostasis, activation, and antitumor function

This study demonstrates that type I IFNs are an early and critical regulator of NK cell numbers, activation, and antitumor activity. Using both IFNAR1- and IFNAR2-deficient mice, as well as an IFNAR1-blocking Ab, we demonstrate that endogenous type I IFN is critical for controlling NK cell-mediated antitumor responses in many experimental tumor models, including protection from methylcholanthrene-induced sarcomas, resistance to the NK cell-sensitive RMA-S tumor and cytokine immunotherapy of lung metastases. Protection from RMA-S afforded by endogenous type I IFN is more potent than that of other effector molecules such as IFN-gamma, IL-12, IL-18, and perforin. Furthermore, cytokine immunotherapy using IL-12, IL-18, or IL-21 was effective in the absence of endogenous type I IFN, however the antimetastatic activity of IL-2 was abrogated in IFNAR-deficient mice, primarily due to a defect in IL-2-induced cytotoxic activity. This study demonstrates that endogenous type I IFN is a central mediator of NK cell antitumor responses.     

Combinational adenovirus-mediated gene therapy and dendritic cell vaccine in combating well-established tumors

Recent developments in tumor immunology and biotechnology have made cancer gene therapy and immunotherapy feasible. The current efforts for cancer gene therapy mainly focus on using immunogenes, chemogenes and tumor suppressor genes. Central to all these therapies is the development of efficient vectors for gene therapy. By far, adenovirus （AdV）-mediated gene therapy is one of the most promising approaches, as has confirmed by studies relating to animal tumor models and clinical trials. Dendritic cells （DCs） are highly efficient, specialized antigen-presenting cells, and DC- based tumor vaccines are regarded as having much potential in cancer immunotherapy. Vaccination with DCs pulsed with tumor peptides, lysates, or RNA, or loaded with apoptotic/necrotic tumor cells, or engineered to express certain cytokines or chemokines could induce significant antitumor cytotoxic T lymphocyte （CTL） responses and antitumor immunity. Although both AdV-mediated gene therapy and DC vaccine can both stimulate antitumor immune responses, their therapeutic efficiency has been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or to growth inhibition of small tumors. However, this approach has been unsuccessful in combating well-established tumors in animal models. Therefore, a major strategic goal of current cancer immunotherapy has become the development of novel therapeutic strategies that can combat well-established tumors, thus resembling real clinical practice since a good proportion of cancer patients generally present with significant disease. In this paper, we review the recent progress in AdV-mediated cancer gene therapy and DC-based cancer vaccines, and discuss combined immunotherapy including gene therapy and DC vaccines. We underscore the fact that combined therapy may have some advantages in combating well-established tumors vis-a-vis either modality administered as a monotherapy.     

Cyclooxygenase-2 inhibitor induces apoptosis in breast cancer cells in an in vivo model of spontaneous metastatic breast cancer

Cyclooxygenase-2 (COX-2) inhibitors are rapidly emerging as a new generation of therapeutic drug in combination with chemotherapy or radiation therapy for the treatment of cancer. The mechanisms underlying its antitumor effects are not fully understood and more thorough preclinical trials are needed to determine if COX-2 inhibition represents a useful approach for prevention and/or treatment of breast cancer. The purpose of this study was to evaluate the growth inhibitory mechanism of a highly selective COX-2 inhibitor, celecoxib, in an in vivo oncogenic mouse model of spontaneous breast cancer that resembles human disease. The oncogenic mice carry the polyoma middle T antigen driven by the mouse mammary tumor virus promoter and develop primary adenocarcinomas of the breast. Results show that oral administration of celecoxib caused significant reduction in mammary tumor burden associated with increased tumor cell apoptosis and decreased proliferation in vivo. In vivo apoptosis correlated with significant decrease in activation of protein kinase B/Akt, a cell survival signaling kinase, with increased expression of the proapoptotic protein Bax and decreased expression of the antiapoptotic protein Bcl-2. In addition, celecoxib treatment reduced levels of proangiogenic factor (vascular endothelial growth factor), suggesting a role of celecoxib in suppression of angiogenesis in this model. Results from these preclinical studies will form the basis for assessing the feasibility of celecoxib therapy alone or in combination with conventional therapies for treatment and/or prevention of breast cancer.     

Interleukin 15 as a promising candidate for tumor immunotherapy

Interleukin 15 participates in the development of important immune antitumor mechanisms. It activates CD8(+) T cells, natural killer (NK) cells, NK T cells, and can promote the formation of antitumor antibodies. IL-15 can also protect T effector cells from the action of T regulatory cells and reverse tolerance to tumor-associated antigens. In pre-clinical studies IL-15 has been found to demonstrate potentiated antitumor effects following pre-association with IL-15Rα, or when used in combination with chemotherapy, adoptive therapy, monoclonal antibodies, and tumor vaccines. Although a clinical trial based on application of IL-15 in tumor patients has already begun, it is important to be aware of its potential side effects, including induction of autoimmunity and promotion of proliferation, survival, and dissemination of some tumor cells.     

Pilot trial of interleukin-2 and zoledronic acid to augment γδ T cells as treatment for patients with refractory renal cell carcinoma

Prior to the advent of VEGF-targeted therapies, renal cell carcinoma (RCC) was among the few solid tumors shown to respond to cytokine-based therapies such as interleukin-2 (IL-2) and interferon alpha. Previous work has shown that aminobisphosphonates, including zoledronic acid (ZA), are capable of activating human Vγ9 Vδ2 T cells in vitro, and these cells can be further expanded with IL-2. Moreover, these Vγ9 Vδ2 T cells have cytolytic activity in vitro to multiple human tumor cell lines. In the current report, we have conducted a pilot trial in patients with metastatic RCC, evaluating different doses of ZA in combination with low-dose IL-2 to determine whether combining these agents can promote in vivo proliferation of Vγ9 Vδ2 T cells and elicit an antitumor response. In 12 patients evaluated, no objective clinical responses were observed by RECIST criteria; however, two patients experienced prolonged stable disease. A modest increase in Vγ9 Vδ2 T-cell frequency could be detected by Day 8 of therapy in four of the nine patients who received at least one cycle of therapy, but not to the magnitude anticipated from preclinical models. Repeated administration of IL-2 and ZA resulted in both a diminished in vivo percentage of Vγ9 Vδ2 T cells as well as impaired expansion in vitro after the first cycle of therapy. These results suggest that repeated administration of IL-2 and ZA, at the doses and schedules used in this trial, may actually inhibit the proliferative capacity of Vγ9 Vδ2 T cell in patients with metastatic RCC.     

Dynamic contrast-enhanced magnetic resonance imaging of sunitinib-induced vascular changes to schedule chemotherapy in renal cell carcinoma xenograft tumors

In an attempt to develop better therapeutic approaches for metastatic renal cell carcinoma (RCC), the combination of the antiangiogenic drug sunitinib with gemcitabine was studied. Using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), we have previously determined that a sunitinib dosage of 20 mg/kg per day increased kidney tumor perfusion and decreased vascular permeability in a preclinical murine RCC model. This sunitinib dosage causing regularization of tumor vessels was selected to improve delivery of gemcitabine to the tumor. DCE-MRI was used to monitor regularization of vasculature with sunitinib in kidney tumors to schedule gemcitabine. We established an effective and nontoxic schedule of sunitinib combined with gemcitabine consisting of pretreatment with sunitinib for 3 days followed by four treatments of gemcitabine at 20 mg/kg given 3 days apart while continuing daily sunitinib treatment. This treatment caused significant tumor growth inhibition resulting in small residual tumor nodules exhibiting giant tumor cells with degenerative changes, which were observed both in kidney tumors and in spontaneous lung metastases, suggesting a systemic antitumor response. The combined therapy caused a significant increase in mouse survival. DCE-MRI monitoring of vascular changes induced by sunitinib, gemcitabine, and both combined showed increased tumor perfusion and decreased vascular permeability in kidney tumors. These findings, confirmed histologically by thinning of tumor blood vessels, suggest that both sunitinib and gemcitabine exert antiangiogenic effects in addition to cytotoxic antitumor activity. These studies show that DCE-MRI can be used to select the dose and schedule of antiangiogenic drugs to schedule chemotherapy and improve its efficacy.     

Which immunological parameters are clinically essential to monitor IL-2 cancer immunotherapy?

The evaluation of the immunobiological changes occuring during IL-2 cancer immunotherapy is not only important to correlate them with the clinical response or to understand the immune mechanism involved in tumor growth control, but also to predict the efficacy of treatment itself. As far as the immune status of patients prior to therapy is concerned, the evidence of the activation of the inflammatory response correlates with resistance to IL-2. Therefore, the evidence of abnormally high pretreatment values of inflammatory response markers, including ESR, CRP, neopterin and SIL-2R, may predict a lack of IL-2 efficacy. In contrast, changes in inflammatory parameters during IL-2 administration have no prognostic significance. The evidence of elevated pretreatment levels of the immunosuppressive cytokine IL-10 has also an unfavourable prognostic significance. At the other side, the evidence of a marked increase in hemopoietic cells involved in tumor cell destruction, such as lymphocytes and eosinophils, as well as in blood levels of antitumor cytokines, such as IL-12, correlates with efficacy of IL-2 cancer immunotherapy. A better definition of the prognostic significance of immunoinflammatory markers will allow us to manipulate and improve host biological response during cancer immunotherapy with IL-2.     

Cancer therapy by biological response modifiers

Biological response modifiers (BRMs) are agents or approaches which can modify the biological response of the host to tumors and thereby are expected to augment the resistance to development or progression of cancer. Recent advances in the technology of genetic engineering and monoclonal antibodies have led to rapid progress in this field. There is an increasing number of genetically engineered cytokines, which appear promising for cancer treatment and are becoming available for clinical trials. These include the interferons, leukin-2, tumor necrosis factor, and colony-stimulating factors. For development of optimal therapeutic protocols with these and a variety of immunomodulatory agents, it appears necessary to develop a detailed understanding of the possible mechanisms of their antitumor effects, and to determine the optimal dose and schedule for altering the antitumor effector mechanisms. BRMs would also be expected to be quite useful in the prevention of cancer. Indeed, in a variety of animal tumor model systems, potent protective effects can be demonstrated. However, the strategies for clinical application of such information have yet to be adequately worked out. One more immediate application of this approach is for the prevention of metastatic spread of tumor cells. BRMs, which stimulate natural killer cell activity, have been shown to strongly protect against dissemination of tumors, and clinical strategies for this important aspect of cancer treatment are being developed.