A Potent Oncolytic Adenovirus Selectively Blocks the STAT3 Signaling Pathway and Potentiates Cisplatin Antitumor Activity in Ovarian Cancer

Interleukin-6 Modulation in Ovarian Cancer Necessitates a Targeted Strategy: From the Approved to Emerging Therapies

Despite significant advances in treatments, ovarian cancer (OC) remains one of the most prevalent and lethal gynecological cancers in women. The frequent detection at the advanced stages has contributed to low survival rates, resistance to various treatments, and disease recurrence. Thus, a more effective approach is warranted to combat OC. The cytokine Interleukin-6 (IL6) has been implicated in various stages of OC development. High IL6 levels are also correlated with a lower survival rate in OC patients. In this current review, we summarized the pivotal roles of IL6 in OC, including the initiation, development, invasion, metastasis, and drug resistance mechanisms. This article systematically highlights how targeting IL6 improves OC outcomes by altering various cancer processes and reports the ongoing clinical trials that would further shape the IL6-based targeted therapies. This review also suggests how combining IL6-targeted therapies with other therapeutic strategies could further enhance their efficacy to combat OC.

SOCS3 inhibiting JAK-STAT pathway enhances oncolytic adenovirus efficacy by potentiating viral replication and T-cell activation

Oncolytic viruses (OVs) are emerging as a potentially useful treatment for malignancies due to the capabilities of direct oncolysis and immune induction. Improving the replication of OVs is an effective approach to enhance the oncolytic effects. Here, we observed that cancer cells with deficiencies in JAK-STAT pathway showed greater sensitivity to oncolytic adenovirus (oAd), and JAK inhibitor could enhance the replication of oAd. Therefore, we constructed a novel oAd expressing SOCS3, a major negative regulator of JAK-STAT pathway, and confirmed that oAd-SOCS3 exhibited a more significant antitumor effect than oAd-Ctrl both in vitro and in vivo. Mechanistically, SOCS3 inhibited the activation of JAK-STAT pathway, resulting in stronger tumor selective replication of oAd and downregulated expression of PD-L1 on cancer cells as well. Both benefits could collectively awaken antitumor immunity. This study highlights the importance of JAK-STAT pathway in viral replication and confirms the treatment of oAd-SOCS3 in potential clinical applications.

Gene Therapy for Malignant and Benign Gynaecological Disorders: A Systematic Review of an Emerging Success Story

Simple Summary

This review discusses all the major advances in gene therapy of gynaecological disorders, highlighting the novel and potentially therapeutic perspectives associated with such an approach. It specifically focuses on the gene therapy strategies against major gynaecological malignant disorders, such as ovarian, cervical, and endometrial cancer, as well as benign disorders, such as uterine leiomyomas, endometriosis, placental, and embryo implantation disorders. The above therapeutic strategies, which employ both viral and non-viral systems for mutation compensation, suicide gene therapy, oncolytic virotherapy, antiangiogenesis and immunopotentiation approaches, have yielded promising results over the last decade, setting the grounds for successful clinical trials.

Abstract

Despite the major advances in screening and therapeutic approaches, gynaecological malignancies still present as a leading cause of death among women of reproductive age. Cervical cancer, although largely preventable through vaccination and regular screening, remains the fourth most common and most lethal cancer type in women, while the available treatment schemes still pose a fertility threat. Ovarian cancer is associated with high morbidity rates, primarily due to lack of symptoms and high relapse rates following treatment, whereas endometrial cancer, although usually curable by surgery, it still represents a therapeutic problem. On the other hand, benign abnormalities, such as fibroids, endometriosis, placental, and embryo implantation disorders, although not life-threatening, significantly affect women’s life and fertility and have high socio-economic impacts. In the last decade, targeted gene therapy approaches toward both malignant and benign gynaecological abnormalities have led to promising results, setting the ground for successful clinical trials. The above therapeutic strategies employ both viral and non-viral systems for mutation compensation, suicide gene therapy, oncolytic virotherapy, antiangiogenesis and immunopotentiation. This review discusses all the major advances in gene therapy of gynaecological disorders and highlights the novel and potentially therapeutic perspectives associated with such an approach.

M11: A Tropism-modified Oncolytic Adenovirus Arming with Tumor-homing Peptide for Advanced Ovarian Cancer Therapies

Oncolytic adenoviruses (OAds) have shown great promise in cancer therapy, but their efficacy has been greatly limited by poor tumor selectivity and highly off-target liver sequestration. Herein, we generate a novel "stealth' and tumor-targeting oncolytic adenovirus vector M0-TMTP1 through inserting TMTP1 (NVVRQ), a tumor homing peptide specifically targeting metastasis, into the hypervariable region 5 (HVR5) of hexon. M0-TMTP1 exhibits increased transduction of tumor cells in vitro. In vivo biodistribution of M0-TMTP1 in an intraperitoneal disseminated ovarian cancer model showed significantly reduced virus load in major organs but apparent aggregation in tumors. The tumor-to-liver ratio of M0-TMTP1 was nearly 5000-fold higher than control adenovirus M0. Further, we armed M0-TMTP1 with trunked BID (tBID), a mitochondrial apoptosis protein, to obtain M11. Combining M11 with cisplatin (DDP) could induce an intensive antitumor effect in vitro and in vivo. Moreover, this combination therapy showed higher biosafety. Taken together, our results suggest that M11 represents a tumor-targeting, efficacious, and relatively nontoxic viro-therapeutic agent, and these findings might offer renewed hope for tumor management.

Understanding and addressing barriers to successful adenovirus-based virotherapy for ovarian cancer

Ovarian cancer is the leading cause of death among women with gynecological cancer, with an overall 5-year survival rate below 50% due to a lack of specific symptoms, late stage at time of diagnosis and a high rate of recurrence after standard therapy. A better understanding of heterogeneity, genetic mutations, biological behavior and immunosuppression in the tumor microenvironment have allowed the development of more effective therapies based on anti-angiogenic treatments, PARP and immune checkpoint inhibitors, adoptive cell therapies and oncolytic vectors. Oncolytic adenoviruses are commonly used platforms in cancer gene therapy that selectively replicate in tumor cells and at the same time are able to stimulate the immune system. In addition, they can be genetically modified to enhance their potency and overcome physical and immunological barriers. In this review we highlight the challenges of adenovirus-based oncolytic therapies targeting ovarian cancer and outline recent advances to improve their potential in combination with immunotherapies.

Truncated Bid Regulates Cisplatin Response via Activation of Mitochondrial Apoptosis Pathway in Ovarian Cancer

Refractoriness to conventional chemotherapy is a major challenge in the treatment of advanced ovarian cancer (OC). There is increasing evidence that mitochondrial priming correlates with cisplatin response in various cancers. Notably, Bim and Bid, two of the proapoptotic BH3-only proteins, are recognized as the most effective inducers of mitochondrial priming in OC. In this study, we constructed two tumor-specific oncolytic adenoviruses (Ads) coding for Bim (Ad-Bim) or truncated Bid (Ad-tBid), respectively, and performed gain-of-function assays in nine OC cell lines. Ad-tBid exhibited significant antitumor efficacy than the controls. On addition of Ad-tBid pretreatment, mito-primed cells displayed more sensitivity to cisplatin both in vitro and ex vivo. We also found that Ad-tBid induced mitochondrial apoptosis in a Bak-dependent manner. Furthermore, a combined cisplatin plus Ad-tBid therapy markedly inhibited tumor growth in a subcutaneous xenotransplanted tumor model. In mice bearing peritoneal disseminated OC, intraperitoneal administration of Ad-tBid potentiated the antitumor effect of cisplatin. Our findings suggest that Ad-tBid enhances cisplatin response in OC cells, establishing the potential treatment of advanced OC via a combination of cisplatin and Ad-tBid.

STAT3 signaling in ovarian cancer: a potential therapeutic target

Accumulating evidence has shown that Signal Transducer and Activator of Transcription 3 (STAT3) is thought to be a promising target for cancer therapy as STAT3 is frequently overexpressed in a wide range of cancer cells as well as clinical specimens, promoting tumor progression. It is widely accepted that STAT3 regulates a variety of cellular processes, such as tumor cell growth, survival, invasion, cancer stem cell-like characteristic, angiogenesis and drug-resistance. In this review, we focus on the role of STAT3 in tumorigenesis in ovarian cancer and discuss the existing inhibitors of STAT3 signaling that can be promisingly developed as the strategies for ovarian cancer therapy.

Expression and Functions of Formyl Peptide Receptor 1 in Drug-Resistant Bladder Cancer

Objective:

To explore the correlation of formyl peptide receptor 1 expression with drug resistance and the functions of formyl peptide receptor 1 in drug-resistant bladder cancer.

Methods:

Expression of formyl peptide receptor 1 in T24 and T24/DDP cisplatin-resistant bladder cancer cell lines was tested by quantitative real-time Polymerase Chain Reaction and Western blotting. After incubation of T24/DDP with N-formyl-Met-Leu-Phe, the phosphor proteins were tested by Western blot analysis. We characterized the functions of formyl peptide receptor 1 in T24/DDP cells by assessing proliferation, migration, and changes of cell cycles.

Results:

Formyl peptide receptor 1 was expressed in both T24 and T24/DDP, and it was overexpressed in T24/DDP compared with T24. Formyl peptide receptor 1 activation promoted the expression of the messenger RNA of resistance-related proteins, such as multidrug resistance-associated protein 1 (MRP1) and lung resistance-related protein (LRP). The expression of 4 signal pathway proteins were upregulated: signal transducer and activator of transcription 3, Janus kinase 2, extracellular regulated protein kinases, and protein kinase B, while the expression of phosphatidylinositol 3-kinase was observed to be downregulated in drug-resistant bladder cancer cells. Formyl peptide receptor 1 activation also improved the expression of phospho-signal transducer and activator of transcription 3 and phospho-extracellular regulated protein kinases 1/2 and promoted the proliferation and migration of T24/DDP cells. In addition, formyl peptide receptor 1 inhibition led to the change in the cell cycle in T24/DDP.

Conclusions:

The overexpression of formyl peptide receptor 1 may be related to drug-resistant bladder cancer and promotes the deterioration of drug-resistant bladder cancer.

Spatial and temporal proteome dynamics of glioma cells during oncolytic adenovirus Delta-24-RGD infection

Glioblastoma multiforme (GBM) is the most common and aggressive type of malignant glioma. Oncolytic adenoviruses are being modified to exploit the aberrant expression of proteins in tumor cells to increase the antiglioma efficacy. E1A mutant adenovirus Delta-24-RGD (DNX-2401) has shown a favorable toxicity profile and remarkable efficacy in a first-in-human phase I clinical trial. However, the comprehensive modulation of glioma metabolism in response to Delta-24-RGD infection is poorly understood. Integrating mass spectrometry based-quantitative proteomics, physical and functional interaction data, and biochemical approaches, we conducted a cell-wide study of cytosolic, nuclear, and secreted glioma proteomes throughout the early time course of Delta-24-RGD infection. In addition to the severe proteostasis impairment detected during the first hours post-infection (hpi), Delta-24-RGD induces a transient inhibition of signal transducer and activator of transcription 3 (STAT3), and transcription factor AP-1 (c-JUN) between 3 and 10hpi, increasing the nuclear factor kappa B (NF-κB) activity at 6hpi. Furthermore, Delta-24-RGD specifically modulates the activation dynamics of protein kinase C (PKC), extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 mitogen-activated protein kinase (p38 MAPK) pathways early in infection. At extracellular level, Delta-24-RGD triggers a time -dependent dynamic production of multitasking cytokines, and chemotactic factors, suggesting potential pleiotropic effects on the immune system reactivation. Taken together, these data help us to understand the mechanisms used by Delta-24-RGD to exploit glioma proteome organization. Further mining of this proteomic resource may enable design and engineering complementary adenoviral based-vectors to increase the specificity and potency against glioma.

Oncolytic virus immunotherapies in ovarian cancer: moving beyond adenoviruses

Ovarian cancer is the 5th most common cancer in UK women with a high relapse rate. The overall survival for ovarian cancer has remained low for decades prompting a real need for new therapies. Recurrent ovarian cancer remains confined in the peritoneal cavity in >80% of the patients, providing an opportunity for locoregional administration of novel therapeutics, including gene and viral therapy approaches. Immunotherapy is an expanding field, and includes oncolytic viruses as well as monoclonal antibodies, immune checkpoint inhibitors, and therapeutic vaccines. Oncolytic viruses cause direct cancer cell cytolysis and immunogenic cell death and subsequent release of tumor antigens that will prime for a potent tumor-specific immunity. This effect may be further enhanced when the viruses are engineered to express, or coadministered with, immunostimulatory molecules. Currently, the most commonly used and well-characterized vectors utilized for virotherapy purposes are adenoviruses. They have been shown to work synergistically with traditional chemotherapy and radiotherapy and have met with success in clinical trials. However, pre-existing immunity and poor in vivo models limit our ability to fully investigate the potential of oncolytic adenovirus as effective immunotherapies which in turn fosters the need to develop alternative viral vectors. In this review we cover recent advances in adenovirus-based oncolytic therapies targeting ovarian cancer and recent advances in mapping immune responses to oncolytic virus therapies in ovarian cancer.

STAT3 inhibition by WP1066 suppresses the growth and invasiveness of bladder cancer cells

Signal transducer and activator of transcription 3 (STAT3) regulates the expression of genes mediating cell survival, proliferation and angiogenesis and is aberrantly activated in various types of malignancies, including bladder cancer. We examined whether it could be a novel therapeutic target for bladder cancer using the STAT3 inhibitor WP1066. In T24 and UMUC-3 bladder cancer cells, 5 µM WP1066 prevented the phosphorylation of STAT3 and 2.5 µM WP1066 decreased cell survival and proliferation significantly (P<0.01). WP1066 also induced apoptosis accompanied by the suppression of the expression of Bcl-2 and Bcl-xL in T24 cells. Moreover, the covered area in a wound and the number of cells invading through a Matrigel chamber decreased significantly (P<0.01) when cells were treated with WP1066. The activities of MMP-2 and MMP-9 were also decreased by treatment with 10 µM WP1066. Our results revealed that using WP1066 to inhibit the STAT3 signaling pathway suppressed the viability and invasiveness of bladder cancer cells effectively and could be a novel therapeutic strategy against bladder cancer.

Myxoma Virus Optimizes Cisplatin for the Treatment of Ovarian Cancer In Vitro and in a Syngeneic Murine Dissemination Model

A therapeutic approach to improve treatment outcome of ovarian cancer (OC) in patients is urgently needed. Myxoma virus (MYXV) is a candidate oncolytic virus that infects to eliminate OC cells. We found that in vitro MYXV treatment enhances cisplatin or gemcitabine treatment by allowing lower doses than the corresponding IC₅₀ calculated for primary OC cells. MYXV also affected OC patient ascites-associated CD14⁺ myeloid cells, one of the most abundant immunological components of the OC tumor environment; without causing cell death, MYXV infection reduces the ability of these cells to secrete cytokines such as IL-10 that are signatures of the immunosuppressive tumor environment. We found that pretreatment with replication-competent but not replication-defective MYXV-sensitized tumor cells to later cisplatin treatments to drastically improve survival in a murine syngeneic OC dissemination model. We thus conclude that infection with replication-competent MYXV before cisplatin treatment markedly enhances the therapeutic benefit of chemotherapy. Treatment with replication-competent MYXV followed by cisplatin potentiated splenocyte activation and IFNγ expression, possibly by T cells, when splenocytes from treated mice were stimulated with tumor cell antigen ex vivo. The impact on immune responses in the tumor environment may thus contribute to the enhanced antitumor activity of combinatorial MYXV-cisplatin treatment.

(E)-2-methoxy-4-(3-(4-methoxyphenyl)prop-1-en-1-yl)phenol suppresses ovarian cancer cell growth via inhibition of ERK and STAT3

In the present study, we synthesized several non-aldehyde analogues of (E)-2,4-bis(p-hydroxyphenyl)-2-butenal which showed anti-cancer effect. Interestingly, among the 16 compounds, we found that (E)-2-methoxy-4-(3-(4-methoxyphenyl)prop-1-en-1-yl)phenol (MMPP) showed the most significant anti-proliferative effect on PA-1 and SK-OV-3 ovarian epithelial cancer cells. MMPP treatment (0-15 µg/mL) induced apoptotic cell death, enhanced the expression of cleaved caspase-3, and cleaved caspase-9 in a concentration dependent manner. Notably, DNA binding activity of STAT3, phosphorylation of extracellular signal-regulated kinase (ERK) and p38 was significantly decreased by MMPP treatment. However, ERK siRNA augmented MMPP-induced inhibitory effect on cell growth rather than p38 siRNA or JNK siRNA. Moreover, combination treatment of MMPP with ERK inhibitor U0126 (10 µM) augmented MMPP-induced inhibitory effect on cell growth and DNA binding activity of STAT3, and enhanced expression of cleaved caspase-3 and cleaved caspase-9. In addition, STAT3 siRNA transfection augmented MMPP-induced cell growth inhibition. In PA-1 bearing xenograft mice model, MMPP (5 mg/kg) suppressed tumor growth significantly. Immunohistochemistry staining showed that the expression levels of p-ERK, PCNA, p-STAT3 were decreased while the expression level of caspase-3 was increased by MMPP treatment. Thus, MMPP may be a promising anti-cancer agent in ovarian epithelial cancer treatment.

Adenovirus-mediated delivery of herpes simplex virus thymidine kinase administration improves outcome of recurrent high-grade glioma

BACKGROUND

This randomized, open-label, multicenter, phase II clinical trial was conducted to assess the anti-tumor efficacy and safety of replication-deficient adenovirus mutant thymidine kinase (ADV-TK) in combination with ganciclovir administration in patients with recurrent high-grade glioma (HGG).

PATIENTS AND METHODS

53 patients with recurrent HGG were randomly allocated to receive intra-arterial cerebral infusion of ADV-TK or conventional treatments. The primary end point was 6-month progression-free survival (PFS-6). Secondary end points included progression-free survival (PFS), overall survival (OS), safety, and clinical benefit. This trial is registered with Clinicaltrials.gov, NCT00870181.

RESULTS

In ADV-TK group, PFS-6 was 54.5%, the median PFS was 29.6 weeks, the median OS was 45.4 weeks, and better survivals were achieved when compared with control group. The one-year PFS and OS were 22.7% and 44.6% in ADV-TK group respectively, and clinical benefit was 68.2%. There are 2 patients alive for more than 4 years without progression in ADV-TK group. In the subgroup of glioblastoma received ADV-TK, PFS-6 was 71.4%, median PFS was 34.9 weeks, median OS was 45.7 weeks respectively, much better than those in control group. The one-year PFS and OS were 35.7% and 50.0% in ADV-TK group respectively. ADV-TK/ganciclovir gene therapy was well tolerated, and no treatment-related severe adverse events were noted.

CONCLUSION

Our study demonstrated a notable improvement of PFS-6, PFS and OS in ADV-TK treated group, and the efficacy and safety appear to be comparable to other reported treatments used for recurrent HGG. ADV-TK gene therapy is therefore a valuable therapeutic option for recurrent HGG.

Association of oncolytic adenoviruses with chemotherapies: an overview and future directions

Oncolytic adenoviruses have been used in different preclinical and clinical studies, showing their capacity to kill tumor cells without major adverse events. However, these studies also underline the limitations of this approach. The efficacy of oncolytic adenoviruses is hampered by their limited ability to transduce some tumor types, their lack of selectivity, and their poor dissemination within tumors. In addition, the host immune response may limit oncolytic adenovirus efficacy. Combining oncolytic adenoviruses with chemotherapeutics constitutes an appealing strategy to increase their potency. The first part of this review describes the molecular basis of oncolytic adenoviruses, their use in preclinical studies and clinical trials, their limitations, and strategies to circumvent these limitations. The second part will focus on studies combining oncolytic adenoviruses with chemotherapeutic drugs, including standard chemotherapeutic drugs, molecularly targeted drugs, and other drugs that have been combined with oncolytic adenoviruses. Finally, based on these studies, we describe future directions and general rules that could be followed to identify chemotherapeutic drugs displaying additive/synergistic effects when combined with oncolytic adenoviruses.

(E)-2,4-Bis(p-hydroxyphenyl)-2-butenal enhanced TRAIL-induced apoptosis in ovarian cancer cells through downregulation of NF-κB/STAT3 pathway

Ovarian cancer is a cancerous growth arising from the ovary and with poor prognosis that usually have resistant to all currently available treatments. Whether (E)-2,4-bis(p-hydroxyphenyl)-2-butenal (butenal) synthesized by Maillard reaction from fructose-tyrosine, has potential therapeutic activity against human ovarian cancer was investigated using two ovarian cancer cell lines (PA-1, SK-OV-3). We found that butenal could inhibit NF-κB/STAT3 activity, thereby inducing apoptotic cell death of ovarian cancer cells. We treated with several concentration of butenal each cell line differently (PA-1; 5, 10 and 15 μg/ml, SK-OV-3; 10, 20 and 30 μg/ml). First, ovarian cancer cell lines exhibited constitutively active NF-κB, and treatment with butenal abolished this activation as indicated by DNA binding activity. Second, butenal suppressed activation of signal transducer and activator of transcription-3 as indicated by decreased phosphorylation and inhibition of Janus kinase-2 phosphorylation. Third, butenal induced expression of pro-apoptotic proteins such as proteolytic cleavage of PARP, Bax and activation of caspase-3, -8 and -9. Lastly, combination of butenal and TRAIL causes enhanced induction of apoptosis. Overall, our results indicate that butenal mediates its anti-proliferative and apoptotic effects through activation of multiple cell signaling pathways and enhances the TRAIL-induced apoptosis. These data suggested that butenal may be a potential anti-cancer agent in ovarian cancer.

Abrogation of constitutive Stat3 activity circumvents cisplatin resistant ovarian cancer

The aim of the present study was to investigate the role of Stat3 in cisplatin resistant ovarian cancer. It was first demonstrated that higher activated Stat3 was detected in cisplatin-resistant ovarian cancer cell lines. To provide evidence that supported the hypothesis that phosphorylated-Stat3 expression may promote cisplatin resistance, ectopic Stat3 was expressed by IL-6 stimulation that partially abrogates Stat3, as opposed to the knock-down of Stat3 by specific siRNA that restores cisplatin sensitivity against ovarian cancer cells. This hypothesis was further confirmed by clinical tumor specimens of ovarian cancer obtained from patients with cisplatin-resistance. Based on these premises, Stattic, an effective small molecular inhibitor of Stat3, was used to inhibit Stat3 activation. The data presented here show that Stattic restored the sensitivity to cisplatin in chemoresistant ovarian cancer by significant reductions in the expression of the anti-apoptosis protein Bcl-2, Bcl-XL, Survivin protein and phosphorylated-Akt levels. Consistent with these observations, this experiment demonstrated the first evidence of Stattic circumvented cisplatin resistance of orthotopic xenograft ovarian cancer in vivo. Altogether, these findings emphasize the importance of Stat3 in cisplatin resistance in ovarian cancer and provide a further impetus to clinically evaluate biological modifiers that may circumvent cisplatin resistance in patients with chemoresistant ovarian cancer.

Early responses of the STAT3 pathway to platinum drugs are associated with cisplatin resistance in epithelial ovarian cancer

Cisplatin resistance remains one of the major obstacles when treating epithelial ovarian cancer. Because oxaliplatin and nedaplatin are effective against cisplatin-resistant ovarian cancer in clinical trials and signal transducer and activator of transcription 3 (STAT3) is associated with cisplatin resistance, we investigated whether overcoming cisplatin resistance by oxaliplatin and nedaplatin was associated with the STAT3 pathway in ovarian cancer. Alamar blue, clonogenic, and wound healing assays, and Western blot analysis were used to compare the effects of platinum drugs in SKOV-3 cells. At an equitoxic dose, oxaliplatin and nedaplatin exhibited similar inhibitory effects on colony-forming ability and greater inhibition on cell motility than cisplatin in ovarian cancer. Early in the time course of drug administration, cisplatin increased the expression of pSTAT3 (Tyr705), STAT3α, VEGF, survivin, and Bcl-X_L, while oxaliplatin and nedaplatin exhibited the opposite effects, and upregulated pSTAT3 (Ser727) and STAT3β. The STAT3 pathway responded early to platinum drugs associated with cisplatin resistance in epithelial ovarian cancer and provided a rationale for new therapeutic strategies to reverse cisplatin resistance.

Chapter eight--Oncolytic adenoviruses for cancer immunotherapy: data from mice, hamsters, and humans

Adenovirus is one of the most commonly used vectors for gene therapy and two products have already been approved for treatment of cancer in China (Gendicine(R) and Oncorine(R)). An intriguing aspect of oncolytic adenoviruses is that by their very nature they potently stimulate multiple arms of the immune system. Thus, combined tumor killing via oncolysis and inherent immunostimulatory properties in fact make these viruses in situ tumor vaccines. When further engineered to express cytokines, chemokines, tumor-associated antigens, or other immunomodulatory elements, they have been shown in various preclinical models to induce antigen-specific effector and memory responses, resulting both in full therapeutic cures and even induction of life-long tumor immunity. Here, we review the state of the art of oncolytic adenovirus, in the context of their capability to stimulate innate and adaptive arms of the immune system and finally how we can modify these viruses to direct the immune response toward cancer.