Rebecca C. Auer

Predictors of a true complete response among disappearing liver metastases from colorectal cancer after chemotherapy

During chemotherapy, some colorectal liver metastases (LMs) disappear on serial imaging. This disappearance may represent a complete response (CR) or a reduction in the sensitivity of imaging during chemotherapy. The objective of the current study was to determine the fate of disappearing LMs (DLMs) and the factors that predict a true CR.

The Oncolytic Poxvirus JX-594 Selectively Replicates in and Destroys Cancer Cells Driven by Genetic Pathways Commonly Activated in Cancers

Oncolytic viruses are generally designed to be cancer selective on the basis of a single genetic mutation. JX-594 is a thymidine kinase (TK) gene-inactivated oncolytic vaccinia virus expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) and lac-Z transgenes that is designed to destroy cancer cells through replication-dependent cell lysis and stimulation of antitumoral immunity. JX-594 has demonstrated a favorable safety profile and reproducible tumor necrosis in a variety of solid cancer types in clinical trials. However, the mechanism(s) responsible for its cancer-selectivity have not yet been well described. We analyzed the replication of JX-594 in three model systems: primary normal and cancer cells, surgical explants, and murine tumor models. JX-594 replication, transgene expression, and cytopathic effects were highly cancer-selective, and broad spectrum activity was demonstrated. JX-594 cancer-selectivity was multi-mechanistic; replication was activated by epidermal growth factor receptor (EGFR)/Ras pathway signaling, cellular TK levels, and cancer cell resistance to type-I interferons (IFNs). These findings confirm a large therapeutic index for JX-594 that is driven by common genetic abnormalities in human solid tumors. This appears to be the first description of multiple selectivity mechanisms, both inherent and engineered, for an oncolytic virus. These findings have implications for oncolytic viruses in general, and suggest that their cancer targeting is a complex and multifactorial process.

Harnessing Oncolytic Virus-mediated Antitumor Immunity in an Infected Cell Vaccine

Treatment of permissive tumors with the oncolytic virus (OV) VSV-Δ51 leads to a robust antitumor T-cell response, which contributes to efficacy; however, many tumors are not permissive to in vivo treatment with VSV-Δ51. In an attempt to channel the immune stimulatory properties of VSV-Δ51 and broaden the scope of tumors that can be treated by an OV, we have developed a potent oncolytic vaccine platform, consisting of tumor cells infected with VSV-Δ51. We demonstrate that prophylactic immunization with this infected cell vaccine (ICV) protected mice from subsequent tumor challenge, and expression of granulocyte-monocyte colony stimulating factor (GM-CSF) by the virus (VSVgm-ICV) increased efficacy. Immunization with VSVgm-ICV in the VSV-resistant B16-F10 model induced maturation of dendritic and natural killer (NK) cell populations. The challenge tumor is rapidly infiltrated by a large number of interferon γ (IFNγ)-producing T and NK cells. Finally, we demonstrate that this approach is robust enough to control the growth of established tumors. This strategy is broadly applicable because of VSVs extremely broad tropism, allowing nearly all cell types to be infected at high multiplicities of infection in vitro, where the virus replication kinetics outpace the cellular IFN response. It is also personalized to the unique tumor antigen(s) displayed by the cancer cell.

Surveillance after curative resection of colorectal cancer.

Surgical resection is the primary treatment modality for patients with localized colorectal cancer, but unfortunately one-third to one-half of these patients will develop a recurrence. If detected early, recurrent disease may be amenable to surgical resection and this provides the rationale for a follow-up strategy in patients with resected colorectal cancer. Despite eight published randomized controlled trials and six published systematic reviews evaluating different follow-up strategies, there is still no consensus as to the appropriateness of follow-up in colorectal cancer patients. In the present article the authors explore the reasons behind the controversy and the arguments used to support each side. They outline the current published guidelines and the data to support these recommendations, including the use of carcinoembryonic antigen (CEA) levels, liver imaging, and colonoscopy. Finally, they speculate on the future developments that may impact on this debate.

Use of helical CT is associated with an increased incidence of postoperative pulmonary emboli in cancer patients with no change in the number of fatal pulmonary emboli.

BACKGROUND Multidetector computed tomography (MDCT) scanning technology has increased the ease with which pulmonary emboli (PE) are evaluated. Our aim was to determine whether the incidence and severity of postoperative PE have changed since adoption of multidetector computed tomography. STUDY DESIGN A prospective postoperative morbidity and mortality database from a single institution was used to identify all cancer patients who experienced a PE within 30 days of thoracic, abdominal, or pelvic operations. The incidence, type (central, segmental, and subsegmental), and severity of PE were examined. RESULTS A total of 295 PE were documented among 47,601 postoperative cancer patients. The incidence of PE increased yearly from 2.3 per 1,000 patients in 2000 to 9.3 per 1,000 patients in 2005 (p < 0.0001). This corresponded to an increasing number of CT scans of the chest performed (6.6 CT scans per 1,000 postoperative patients in 2000 versus 45 in 2005; p < 0.0001). The increased incidence was because of a 7.8% (CI, 4.0 to 11.7) and 5.4% (CI, 4.1 to 6.7) average annual increase in segmental and subsegmental PE, respectively. There was no change in the number of central (0.1%; CI, -1.0 to 1.12) PE. Overall incidence of fatal PE was 0.4 and did not change during the time period (p = 0.3). A central PE was more commonly associated with hypoxia, ICU admission, and 30-day mortality (33% versus 5% for peripheral; p = 0.02). CONCLUSIONS Chest CT scans are being performed more frequently on postoperative cancer patients and have resulted in an increased diagnosis of peripheral PE. The clinical significance of, and optimal treatment for, diagnosed subsegmental PE are incompletely defined.

Complement inhibition prevents oncolytic vaccinia virus neutralization in immune humans and cynomolgus macaques.

Oncolytic viruses (OVs) have shown promising clinical activity when administered by direct intratumoral injection. However, natural barriers in the blood, including antibodies and complement, are likely to limit the ability to repeatedly administer OVs by the intravenous route. We demonstrate here that for a prototype of the clinical vaccinia virus based product Pexa-Vec, the neutralizing activity of antibodies elicited by smallpox vaccination, as well as the anamnestic response in hyperimmune virus treated cancer patients, is strictly dependent on the activation of complement. In immunized rats, complement depletion stabilized vaccinia virus in the blood and led to improved delivery to tumors. Complement depletion also enhanced tumor infection when virus was directly injected into tumors in immunized animals. The feasibility and safety of using a complement inhibitor, CP40, in combination with vaccinia virus was tested in cynomolgus macaques. CP40 pretreatment elicited an average 10-fold increase in infectious titer in the blood early after the infusion and prolonged the time during which infectious virus was detectable in the blood of animals with preexisting immunity. Capitalizing on the complement dependence of antivaccinia antibody with adjunct complement inhibitors may increase the infectious dose of oncolytic vaccinia virus delivered to tumors in virus in immune hosts.

Maraba MG1 Virus Enhances Natural Killer Cell Function via Conventional Dendritic Cells to Reduce Postoperative Metastatic Disease

This study characterizes the ability of novel oncolytic rhabdoviruses (Maraba MG1) to boost natural killer (NK) cell activity. Our results demonstrate that MG1 activates NK cells via direct infection and maturation of conventional dendritic cells. Using NK depletion and conventional dendritic cells ablation studies in vivo, we established that both are required for MG1 efficacy. We further explored the efficacy of attenuated MG1 (nonreplicating MG1-UV(2min) and single-cycle replicating MG1-Gless) and demonstrated that these viruses activate conventional dendritic cells, although to a lesser extent than live MG1. This translates to equivalent abilities to remove tumor metastases only at the highest viral doses of attenuated MG1. In tandem, we characterized the antitumor ability of NK cells following preoperative administration of live and attenuated MG1. Our results demonstrates that a similar level of NK activation and reduction in postoperative tumor metastases was achieved with equivalent high viral doses concluding that viral replication is important, but not necessary for NK activation. Biochemical characterization of a panel of UV-inactivated MG1 (2-120 minutes) revealed that intact viral particle and target cell recognition are essential for NK cell-mediated antitumor responses. These findings provide mechanistic insight and preclinical rationale for safe perioperative virotherapy to effectively reduce metastatic disease following cancer surgery.

Perioperative Influenza Vaccination Reduces Postoperative Metastatic Disease by Reversing Surgery-Induced Dysfunction in Natural Killer Cells

Purpose: Surgical removal of solid primary tumors is an essential component of cancer treatment. Surgery-induced dysfunction in natural killer (NK) cells has been linked to the development of metastases in animal models and patients with cancer. We investigated the activation of NK cells using influenza vaccine in the perioperative period to eradicate micrometastatic disease. Experimental Design: Both the B16lacZ and 4T1 tumor models in immunocompetent mice were used to assess the in vivo efficacy of perioperative influenza vaccine administration. In healthy human donors and cancer surgery patients, we assessed NK cell function pre- and post-influenza vaccination using both in vivo and ex vivo assays. Results: Using the TLR3 agonist poly(I:C), we showed as proof-of-principle that perioperative administration of a nonspecific innate immune stimulant can inhibit surgery-induced dysfunction in NK cells and attenuate metastases. Next, we assessed a panel of prophylactic vaccines for NK cell activation and determined that inactivated influenza vaccine was the best candidate for perioperative administration. Perioperative influenza vaccine significantly reduced tumor metastases and improved NK cytotoxicity in preclinical tumor models. Significantly, IFNα is the main cytokine mediator for the therapeutic effect of influenza vaccination. In human studies, influenza vaccine significantly enhanced NK cell activity in healthy human donors and cancer surgery patients. Conclusion: These results provide the preclinical rationale to pursue future clinical trials of perioperative NK cell activation, using vaccination in cancer surgery patients. Research into perioperative immune therapy is warranted to prevent immune dysfunction following surgery and eradicate metastatic disease. Clin Cancer Res; 19(18); 5104–15. ©2013 AACR.

ORFV: A Novel Oncolytic and Immune Stimulating Parapoxvirus Therapeutic

Replicating viruses for the treatment of cancer have a number of advantages over traditional therapeutic modalities. They are highly targeted, self-amplifying, and have the added potential to act as both gene-therapy delivery vehicles and oncolytic agents. Parapoxvirus ovis or Orf virus (ORFV) is the prototypic species of the Parapoxvirus genus, causing a benign disease in its natural ungulate host. ORFV possesses a number of unique properties that make it an ideal viral backbone for the development of a cancer therapeutic: it is safe in humans, has the ability to cause repeat infections even in the presence of antibody, and it induces a potent T(h)-1-dominated immune response. Here, we show that live replicating ORFV induces an antitumor immune response in multiple syngeneic mouse models of cancer that is mediated largely by the potent activation of both cytokine-secreting, and tumoricidal natural killer (NK) cells. We have also highlighted the clinical potential of the virus by demonstration of human cancer cell oncolysis including efficacy in an A549 xenograft model of cancer.

Sensitivity of cervical carcinoma cells to vesicular stomatitis virus-induced oncolysis: potential role of human papilloma virus infection.

High‐risk carcinogenic subtypes of human papilloma virus (HPV) are associated with the development of squamous cell carcinomas of the cervix (CC) and a subset of head and neck (HNSCC). Recurrent metastatic diseases of these sites display a dismal prognosis. Therefore, there is an urgent need to uncover innovative therapeutic strategies in this clinical setting. Oncolytic viruses, including vesicular stomatitis virus (VSV), were identified due to their ability to specifically target tumor cells that generally display defects in interferon (IFN) signaling. HPV expressed proteins can inhibit IFN signaling; therefore, HPV‐infected cells may be particularly sensitive to VSV oncolysis. In this study, we evaluated the sensitivity of four CC (HPV+) and four HNSCC (HPV−) derived cell lines to VSV oncolysis. Interestingly, the CC cell lines were consistently more sensitive to VSV cytotoxicity than the HNSCC cell lines tested. Exogenous IFN addition or infection with two attenuated VSV variants that are more susceptible to IFN inhibition failed to attenuate VSV oncolysis in hypersensitive CC cell lines. Furthermore, the expression of HPV‐E6, that inhibits IFN receptor signaling, in the VSV‐resistant HNSCC cell line SCC25 attenuated VSV‐induced IFN response and significantly enhanced VSV cytotoxicity. Finally, differential VSV infection and replication was confirmed in xenograft murine tumor models and explant tumor tissues from two patients with CC. Taken together, these results demonstrate that HPV‐infected cells are susceptible to oncolytic virus therapy and that this approach may represent a novel therapeutic approach in HPV positive CC and HNSCC patients.