Mechanistic insights into oncolytic adenovirus therapy

Abstract

The effects of cancer immunotherapy are based on activating and utilizing the immune system to fight cancer cells. In this thesis, a form of immunotherapy, specifically oncolytic adenoviruses, were studied. Immunotherapies are costly to produce and different oncolytic viruses are used in relatively high concentrations and amounts when cancer patients are treated. Thus we wanted to optimize adenovirus vector design, enhance the delivery of adenoviruses to the tumor as well as define and show the immunological response to the adenovirus vector we have developed. It was shown, the physical and functional titers of the produced vectors were relatively stable. However, production was negatively affected if very large constructs (such as antibodies) were inserted or more than five mutations were made to the virus genome. Adenoviruses are attractive vectors for example due to their good safety profile and high production concentrations. When oncolytic virotherapy was originally conceptualized, it was believed that the lytic effect of the virus was driving the benefits for patients. Later, it was shown that other signaling events, such as danger- and pathogen-associated molecular pattern signaling, also play important roles, maybe even more so than virus-induced lysis of cancer cells. Therefore, pattern recognition receptor (PRR) signaling during an oncolytic adnovirus called TILT-123 infection was studied. TILT-123 induced alarmin release through PRRs (such as AIM2) that trigged the activation of immunostimulating signaling cascades, leading to immune-cell activation and tumor clearance. The knowledge of which signaling cascades are activated during infection can be used to further enhance effects of TILT-123 and be extended to enhance the efficacy of other virotherapeutics as well. Most humans have naturally encountered adenovirus and thus many have immune memory towards it. Therefore, when adenovirus vectors are administered intravenously, the pre-existing immunity among other virus clearing reactions, leads to unwanted clearance of the virions from the blood, before the vectors can reach their target. Consequently, we hypothesized that if a mixture of both TILT-123 and tumor infiltrating lymphocytes also known as TILs are administered intravenously a higher efficacymay be achieved. Indeed, TILT-123 did bind to the surface of T cells. When administered simultaneously, the treatment led to a positive tumor-clearing effect in vivo. Unfortunately, some cancer types are still hard to treat. For example, ovarian cancers are often diagnosed at late stages when the tumor size and metastases may hinder effective treatment of the disease. Furthermore, the tumor microenvironment in ovarian cancers is often immunosuppressive. To solve these issues, the effects of TILT-123 on ovarian cancer was studied. It was shown that TILT-123 can be employed to treat ovarian cancer. TILT-123 treatment modified the immunosuppressive microenvironment and enabled a more successful combinatorial treatment with T cell therapy.

Syövän hoitoon voidaan valjastaa viruksia. Tämän takia virusten tuottoon vaikuttavia tekijöitä on syytä tutkia. Tutkimuksessa huomattiin, että adenovirus on suhteellisen kestävä vektori, tuotettujen viruspartikkeleiden määrä ja infektiivisyys pysyy hyvin tasaisena, mutta jos genomiin tehdään 5 tai enemmän muutaatiota, tämä vaikuttaa tuottoon negatiivisesti. Myös isojen konstruktien, kuten vasta-aineita koodaavien geenien, lisääminen genomiin vaikutti negatiivisesti tuoton laatuun. Munasarjasyöpä on usein hankalasti hoidettava tauti, jossa kasvaimen mikroympäristö on hyvin immunosuppressiivinen. TILT-123 on adenovirus johon on lisätty kaksi immuunipuolustusta aktivoivaa geeniä; TNFa ja IL-2. Kun TILT-123 virusta tutkittiin munasarjasyövän hoitomuotona huomattiin, että vrus aktivoi immuunipuolustusta tehokkaasti ja edesauttoi T soluterapian toimivuutta. Virusinfektion aikana, solut ilmoittavat monien signalointireittien kautta infektiosta immuunipuolustukselle. Esimerkiksi DAMP ja PAMP signalointi saa immuunipuolustuksen aktivoitumaan, esimerkiksi infektoitua syöpäsolua vastaan. Tutkimuksessamme todettiin, että TILT-123 aktivoi DAMP ja PAMP singalointikaskadit.