Analysis of a hit-and-run tumor model by HPV in oropharyngeal cancers.

Several viruses are known to be associated with the development of certain cancers, including human papilloma virus (HPV), an established causative agent for a range of anogenital and head and neck cancers. However, the causality has been based on the presence of the virus, or its genetic material, in the sampled tumors. We have long wondered if viruses cause cancer via a "hit and run" mechanism such that they are no longer present in the resulting tumors. Here, we hypothesize that the absence of viral genes from the tumor does not necessarily exclude the viral aetiology. To test this, we used an HPV-driven oropharyngeal cancer (OPC) tumor model and CRISPR to delete the viral oncogene, E7. Indeed, the genetic removal of HPV E7 oncogene eliminates tumors in vivo. Remarkably, E7 deleted tumors recurred over time and develop new mutations not previously seen in HPV+ OPC tumors. Importantly, a number of these new mutations are found to be already present in HPV- OPC tumors.

Genetic deletion of HPV E7 oncogene effectively regresses HPV driven oral squamous carcinoma tumour growth.

The major HPV oncogenes, E6 and E7, are known for its notoriety in driving the carcinogenic process in human papilloma virus (HPV) driven cancers. It is well-established that the removal of E7 dampens HPV cancer cell growth and proliferation. This has made E7 an attractive target for HPV cancers. Seminal work from our laboratory employed a CRISPR editing approach to delete E7 which resulted in the effective elimination of HPV+ cervical cancer tumours in vivo. We have also successfully delayed HPV+ tumour growth in vivo with aurora kinase (AURK) inhibitors, an effect which is strongly sensitized by the presence of E7. Unlike our previous observations in cervical cancer cells, in vitro targeting of E6/E7 have only resulted in partial killing of HPV+ oral squamous carcinoma (OSC) cells. However, the effect of sustained removal of E7 on HPV+ OSC tumour growth have not been explored. In this study, we investigated a staggered combination of aurora kinase inhibition, using alisertib, followed by CRISPR editing of E7, to determine if this would lead to better HPV+ OSC killing. Remarkably, genetic deletion of E7 alone was sufficient to effectively regress established HPV+ OSC tumours in vivo suggesting that E7 is essential in the maintenance of HPV+ OSC cancers.

Alpelisib and radiotherapy treatment enhances Alisertib-mediated cervical cancer tumor killing.

Human papilloma virus (HPV) is the main causative agent in cervical cancers. High-risk HPV cancers, including cervical cancer, are driven by major HPV oncogene, E6 and E7, which promote uncontrolled cell growth and genomic instability. We have previously shown that the presence of HPV E7 sensitizes cells to inhibition of aurora kinases (AURKs), which regulates the control of cell entry into and through mitosis. Such treatment is highly effective at eliminating early tumors and reducing large, late tumors. In addition, the presence of HPV oncogenes also sensitizes cells to inhibition of phosphoinositide 3-kinases (PI3Ks), a family of enzymes involved in cellular functions such as cell growth and proliferation. Using MLN8237 (Alisertib), an oral, selective inhibitor of AURKs, we investigated whether Alisertib treatment can improve tumor response when combined with either radiotherapy (RT) treatment or with a PI3K inhibitor, BYL719 (Alpelisib). Indeed, both RT and Alpelisib significantly improved Alisertib-mediated tumor killing, and the promising achieved results warrant further development of these combinations, and potentially translating them to the clinics.