Tumor-targeting bacteria as immune stimulants - the future of cancer immunotherapy?

Cancer immunotherapies have been widely hailed as a breakthrough for cancer treatment in the last decade, epitomized by the unprecedented results observed with checkpoint blockade. Even so, only a minority of patients currently achieve durable remissions. In general, responsive patients appear to have either a high number of tumor neoantigens, a preexisting immune cell infiltrate in the tumor microenvironment, or an 'immune-active' transcriptional profile, determined in part by the presence of a type I interferon gene signature. These observations suggest that the therapeutic efficacy of immunotherapy can be enhanced through strategies that release tumor neoantigens and/or produce a pro-inflammatory tumor microenvironment. In principle, exogenous tumor-targeting bacteria offer a unique solution for improving responsiveness to immunotherapy. This review discusses how tumor-selective bacterial infection can modulate the immunological microenvironment of the tumor and the potential for combination with cancer immunotherapy strategies to further increase therapeutic efficacy. In addition, we provide a perspective on the clinical translation of replicating bacterial therapies, with a focus on the challenges that must be resolved to ensure a successful outcome.

Equity of travel to access surgery and radiation therapy for lung cancer in New Zealand.

PURPOSE: Centralisation of lung cancer treatment can improve outcomes, but may result in differential access to care for those who do not reside within treatment centres. METHODS: We used national-level cancer registration and health care access data and used Geographic Information Systems (GIS) methods to determine the distance and time to access first relevant surgery and first radiation therapy among all New Zealanders diagnosed with lung cancer (2007-2019; N = 27,869), and compared these outcomes between ethnic groups. We also explored the likelihood of being treated at a high-, medium-, or low-volume hospital. Analysis involved both descriptive and adjusted logistic regression modelling. RESULTS: We found that Maori tend to need to travel further (with longer travel times) to access both surgery (median travel distance: Maori 57 km, European 34 km) and radiation therapy (Maori 75 km, European 35 km) than Europeans. Maori have greater odds of living more than 200 km away from both surgery (adjusted odds ratio [aOR] 1.83, 95% CI 1.49-2.25) and radiation therapy (aOR 1.41, 95% CI 1.25-1.60). CONCLUSIONS: Centralisation of care may often improve treatment outcomes, but it also makes accessing treatment even more difficult for populations who are more likely to live rurally and in deprivation, such as Maori.

Access to and Timeliness of Lung Cancer Surgery, Radiation Therapy, and Systemic Therapy in New Zealand: A Universal Health Care Context.

PURPOSE: Lung cancer is the biggest cancer killer of indigenous peoples worldwide, including Maori people in New Zealand. There is some evidence of disparities in access to lung cancer treatment between Maori and non-Maori patients, but an examination of the depth and breadth of these disparities is needed. Here, we use national-level data to examine disparities in access to surgery, radiation therapy and systemic therapy between Maori and European patients, as well as timing of treatment relative to diagnosis. METHODS: We included all lung cancer registrations across New Zealand from 2007 to 2019 (N = 27,869) and compared access with treatment and the timing of treatment using national-level inpatient, outpatient, and pharmaceutical records. RESULTS: Maori patients with lung cancer appeared less likely to access surgery than European patients (Maori, 14%; European, 20%; adjusted odds ratio [adj OR], 0.82 [95% CI, 0.73 to 0.92]), including curative surgery (Maori, 10%; European, 16%; adj OR, 0.72 [95% CI, 0.62 to 0.84]). These differences were only partially explained by stage and comorbidity. There were no differences in access to radiation therapy or systemic therapy once adjusted for confounding by age. Although it appeared that there was a longer time from diagnosis to radiation therapy for Maori patients compared with European patients, this difference was small and requires further investigation. CONCLUSION: Our observation of differences in surgery rates between Maori and European patients with lung cancer who were not explained by stage of disease, tumor type, or comorbidity suggests that Maori patients who may be good candidates for surgery are missing out on this treatment to a greater extent than their European counterparts.

Emergency presentation prior to lung cancer diagnosis: A national-level examination of disparities and survival outcomes.

OBJECTIVES: A recent multinational investigation of emergency presentation within 30 days of cancer diagnosis, conducted within the International Cancer Benchmarking Programme (ICBP), observed that New Zealand had the highest rate of emergency presentation prior to lung cancer diagnosis compared to other similar countries. Here we use national-level health data to further investigate these trends, focussing on ethnic disparities in emergency presentation prior to lung cancer diagnosis. We have also compared survival outcomes between those who had an emergency presentation in the preceding 30 days to those who did not. MATERIALS AND METHODS: Our study included all lung cancer registrations between 2007 and 2019 on the New Zealand Cancer Registry (N = 27,869), linked to national hospitalisation and primary healthcare data. We used descriptive (crude and age-standardised proportions) and logistic regression (crude and adjusted odds ratios) analyses to examine primary care access prior to cancer diagnosis, emergency hospitalisation up to and including 30 days prior to diagnosis, and one-year mortality post-diagnosis, both for the total population and between ethnicities. Regression models adjusted for age, sex, deprivation, rurality, comorbidity, tumour type and stage. RESULTS: We found stark disparities by ethnic group, with 62% of Pacific peoples and 54% of Maori having an emergency presentation within 30 days prior to diagnosis, compared to 47% of Europeans. These disparities remained after adjusting for multiple covariates including comorbidity and deprivation (adj. OR: Maori 1.21, 95% CI 1.13-1.30; Pacific 1.50, 95% CI 1.31-1.71). Emergency presentation was associated with substantially poorer survival outcomes across ethnic groups (e.g. 1-year mortality for Maori: no emergency presentation 50%, emergency presentation 79%; adj. OR 2.40, 95% CI 2.10-2.74). CONCLUSIONS: These observations reinforce the need for improvements in the early detection of lung cancer, particularly for Maori and Pacific populations, with a view to preventing diagnosis of these cancers in an emergency setting.

Prognostic modelling of clinical outcomes after first-time acute coronary syndrome in New Zealand.

OBJECTIVE: The Multi-Ethnic New Zealand Study of Acute Coronary Syndromes (MENZACS) was established to investigate the drivers of secondary events after first-time acute coronary syndrome (ACS), including addressing inequitable outcomes by ethnicity. Herein, the first clinical outcomes and prognostic modelling approach are reported. METHODS: First, in 28 176 New Zealanders with first-time ACS from a national registry, a clinical summary score for predicting 1-year death/cardiovascular readmission was created using Cox regression of 20 clinical variables. This score was then calculated in the 2015 participant MENZACS study to represent clinical risk. In MENZACS, Cox regression was used to assess N-terminal pro-B-type natriuretic peptide (NT-proBNP) as a prognostic marker for death/cardiovascular readmission in four models, adjusting for (1) age and sex; (2) age, sex, ethnicity; (3) clinical summary score; (4) clinical summary score and ethnicity. RESULTS: Of the 2015 MENZACS participants (mean age 61 years, 79% male, 73% European, 14% Maori, 5% Pacific people), 2003 were alive at discharge. Of the 2003, 416 (20.8%) experienced all-cause death/cardiovascular readmission over a median of 3.5 years. In a simple model, age, male sex, Maori ethnicity and NT-proBNP levels were significant predictors of outcome. After adjustment for the clinical summary score, which includes age and sex, NT-proBNP and ethnicity were no longer statistically significant: log2(NT-proBNP) hazard ratio (HR) 1.03, 95% confidence interval (95% CI) 0.98 to 1.08, p=0.305; Maori ethnicity HR 1.26, 95% CI 0.97 to 1.62, p=0.084. CONCLUSIONS: In 2015 patients with first-time ACS, recurrent events were common (20.8%). Increasing NT-proBNP levels and Maori ethnicity were predictors of death/cardiovascular readmission, but not after adjustment for the 20 clinical risk factors represented by the clinical summary score. TRIAL REGISTRATION NUMBER: ACTRN12615000676516.

Evaluation of Novel Inhibitors of Tryptophan Dioxygenases for Enzyme and Species Selectivity Using Engineered Tumour Cell Lines Expressing Either Murine or Human IDO1 or TDO2.

Indoleamine 2, 3-dioxygenase 1 (IDO1) is commonly expressed by cancers as a mechanism for evading the immune system. Preclinical and clinical studies have indicated the potential of combining IDO1 inhibitors with immune therapies for the treatment of cancer, strengthening an interest in the discovery of novel dioxygenase inhibitors for reversing tumour-mediated immune suppression. To facilitate the discovery, development and investigation of novel small molecule inhibitors of IDO1 and its hepatic isozyme tryptophan dioxygenase (TDO2), murine tumour cells were engineered to selectively express either murine or human IDO1 and TDO2 for use as tools to dissect both the species specificity and isoenzyme selectivity of newly discovered inhibitors. Lewis lung carcinoma (LLTC) lines were engineered to express either murine or human IDO1 for use to test species selectivity of the novel inhibitors; in addition, GL261 glioma lines were engineered to express either human IDO1 or human TDO2 and used to test the isoenzyme selectivity of individual inhibitors in cell-based assays. The 20 most potent inhibitors against recombinant human IDO1 enzyme, discovered from a commissioned screening of 40,000 compounds in the Australian WEHI compound library, returned comparable IC50 values against murine or human IDO1 in cell-based assays using the LLTC-mIDO1 and LLTC-hIDO1 line, respectively. To test the in vivo activity of the hits, transfected lines were inoculated into syngeneic C57Bl/6 mice. Individual LLTC-hIDO1 tumours showed variable expression of human IDO1 in contrast to GL261-hIDO1 tumours which were homogenous in their IDO1 expression and were subsequently used for in vivo studies. W-0019482, the most potent IDO1 inhibitor identified from cell-based assays, reduced plasma and intratumoural ratios of kynurenine to tryptophan (K:T) and delayed the growth of subcutaneous GL261-hIDO1 tumours in mice. Synthetic modification of W-0019482 generated analogues with dual IDO1/TDO2 inhibitory activity, as well as inhibitors that were selective for either TDO2 or IDO1. These results demonstrate the versatility of W-0019482 as a lead in generating all three subclasses of tryptophan dioxygenase inhibitors which can be applied for investigating the individual roles and interactions between IDO1 and TDO2 in driving cancer-mediated immune suppression.

Stimulator of interferon genes (STING) activation exacerbates experimental colitis in mice.

Detection of cytoplasmic DNA by the host's innate immune system is essential for microbial and endogenous pathogen recognition. In mammalian cells, an important sensor is the stimulator of interferon genes (STING) protein, which upon activation by bacterially-derived cyclic dinucleotides (cDNs) or cytosolic dsDNA (dsDNA), triggers type I interferons and pro-inflammatory cytokine production. Given the abundance of bacterially-derived cDNs in the gut, we determined whether STING deletion, or stimulation, acts to modulate the severity of intestinal inflammation in the dextran sodium sulphate (DSS) model of colitis. DSS was administered to Tmem173gt (STING-mutant) mice and to wild-type mice co-treated with DSS and a STING agonist. Colitis severity was markedly reduced in the DSS-treated Tmem173gt mice and greatly exacerbated in wild-type mice co-treated with the STING agonist. STING expression levels were also assessed in colonic tissues, murine bone marrow derived macrophages (BMDMs), and human THP-1 cells. M1 and M2 polarized THP-1 and murine BMDMs were also stimulated with STING agonists and ligands to assess their responses. STING expression was increased in both murine and human M1 polarized macrophages and a STING agonist repolarized M2 macrophages towards an M1-like subtype. Our results suggest that STING is involved in the host's response to acutely-induced colitis.

Expression of a constitutively active human STING mutant in hematopoietic cells produces an Ifnar1-dependent vasculopathy in mice.

STING-associated vasculopathy with onset in infancy (SAVI) is an autoinflammatory disorder characterized by blood vessel occlusions, acral necrosis, myositis, rashes, and pulmonary inflammation that are the result of activating mutations in the STimulator of Interferon Genes (STING). We generated a transgenic line that recapitulates many of the phenotypic aspects of SAVI by targeting the expression of the human STING-N154S-mutant protein to the murine hematopoietic compartment. hSTING-N154S mice demonstrated failure to gain weight, lymphopenia, progressive paw swelling accompanied by inflammatory infiltrates, severe myositis, and ear and tail necrosis. However, no significant lung inflammation was observed. X-ray microscopy imaging revealed vasculopathy characterized by arteriole occlusions and venous thromboses. Type I interferons and proinflammatory mediators were elevated in hSTING-N154S sera. Importantly, the phenotype was prevented in hSTING-N154S mice lacking the type I interferon receptor gene (Ifnar1). This model, based on a mutant human STING protein, may shed light on the pathophysiological mechanisms operative in SAVI.

Mapping a route to Indigenous engagement in cancer genomic research.

Precision oncology guided by genomic research has an increasingly important role in the care of people with cancer. However, substantial inequities remain in cancer outcomes of Indigenous peoples, including Indigenous Maori in Aotearoa New Zealand (New Zealand). These inequities will be perpetuated unless deliberate steps are taken to include Indigenous peoples in all parts of cancer research-as research participants, in research leadership, and in research governance. This approach is especially important when there have been historical breaches of trust that have discouraged their participation in health research. This Personal View describes a precision oncology research roadmap for neuroendocrine tumour research, which seeks to reflect the values of New Zealand's Indigenous Maori people. This roadmap includes facilitating ongoing dialogue, Maori leadership, reciprocity, agreed kawa (guiding principles), tikanga (cultural protocols), and honest monitoring of what is and what is not being achieved. We challenge cancer researchers worldwide to generate locally appropriate roadmaps that honestly assess their practices to benefit Indigenous people internationally.

Recurrent loss of heterozygosity correlates with clinical outcome in pancreatic neuroendocrine cancer.

Pancreatic neuroendocrine tumors (pNETs) are uncommon cancers arising from pancreatic islet cells. Here we report the analysis of gene mutation, copy number, and RNA expression of 57 sporadic well-differentiated pNETs. pNET genomes are dominated by aneuploidy, leading to concordant changes in RNA expression at the level of whole chromosomes and chromosome segments. We observed two distinct patterns of somatic pNET aneuploidy that are associated with tumor pathology and patient prognosis. Approximately 26% of the patients in this series had pNETs with genomes characterized by recurrent loss of heterozygosity (LoH) of 10 specific chromosomes, accompanied by bi-allelic MEN1 inactivation and generally poor clinical outcome. Another ~40% of patients had pNETs that lacked this recurrent LoH pattern but had chromosome 11 LoH, bi-allelic MEN1 inactivation, and universally good clinical outcome. The somatic aneuploidy allowed pathogenic germline variants (e.g., ATM) to be expressed unopposed, with RNA expression patterns showing inactivation of downstream tumor suppressor pathways. No prognostic associations were found with tumor morphology, single gene mutation, or expression of RNAs reflecting the activity of immune, differentiation, proliferative or tumor suppressor pathways. In pNETs, single gene mutations appear to be less important than aneuploidy, with MEN1 the only statistically significant recurrently mutated driver gene. In addition, only one pNET in the series had clearly actionable single nucleotide variants (SNVs) (in PTEN and FLCN) confirmed by corroborating RNA expression changes. The two clinically relevant patterns of LoH described here define a novel oncogenic mechanism and a plausible route to genomic precision oncology for this tumor type.

Connexin hemichannel induced vascular leak suggests a new paradigm for cancer therapy.

It is 40 years since cancer growth was correlated with neovascularisation. Anti-angiogenic drugs remain at the forefront of cancer investigations but progress has been disappointing and unexpected toxicities are emerging. Gap junction channels are implicated in lesion spread following injury, with channel blockers shown to improve healing; in particular preventing vascular disruption and/or restoring vascular integrity. Here we briefly review connexin roles in vascular leak and endothelial cell death that occurs following acute wounds and during chronic disease, and how connexin channel regulation has been used to ameliorate vascular disruption. We then review chronic inflammatory disorders and trauma in the eye, concluding that vascular disruption under these conditions mimics that seen in tumours, and can be prevented with connexin hemichannel modulation. We apply this knowledge to tumour vessel biology, proposing that contrary to current opinion, these data suggest a need to protect, maintain and/or restore cancer vasculature. This may lead to reduced tumour hypoxia, promote the survival of normal cells, and enable improved therapeutic delivery or more effective radiation therapy.

Labeling of oxidizable proteins with a photoactivatable analog of the antitumor agent DMXAA: evidence for redox signaling in its mode of action.

The signaling pathway(s) and molecular target(s) for 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a tumor vascular disrupting agent in late stages of clinical development, are still undefined. As an approach toward identifying potential targets for DMXAA, a tritiated azido-analog of DMXAA was used to probe for cellular binding proteins. More than 20 cytosolic proteins from murine splenocytes, RAW 264.7 cells, and the HECPP immortalized endothelial cells were photoaffinity-labeled. Although no protein domain, fold, or binding site for a specific ligand was found to be shared by all the candidate proteins, essentially all were noted to be oxidizable proteins, implicating a role for redox signaling in the action of DMXAA. Consistent with this hypothesis, DMXAA caused an increase in concentrations of reactive oxygen species (ROS) in RAW264.7 cells during the first 2 hours. This increase in ROS was suppressed in the presence of the antioxidant, N-acetyl-L-cysteine, which also suppressed DMXAA-induced cytokine production in the RAW 264.7 cells with no effects on cell viability. Short interfering RNA (siRNA)-mediated knockdown of one of the photoaffinity-labeled proteins, superoxide dismutase 1, an ROS scavenger, resulted in an increase in tumor necrosis factor-alpha production by RAW 264.7 cells in response to DMXAA compared with negative or positive controls transfected with nontargeting or lamin A/C-targeting siRNA molecules, respectively. The results from these lines of study all suggest that redox signaling plays a central role in cytokine induction by DMXAA.

Transfer of bisphenol A across the human placenta.

OBJECTIVE: The objective of the investigation was to study placental transfer and conjugation of bisphenol A (BPA) across the human placenta. STUDY DESIGN: Human placentae obtained from healthy term singleton pregnancies were utilized in a dual recirculating model of ex vivo placental perfusion. Seven placentae were perfused with BPA (10 ng/mL) added to the maternal perfusate for 180 minutes. Antipyrine and fluorescein isothiocyanate dextran were used as positive and negative controls, respectively, to validate integrity of the circuits. Concentrations of BPA and its conjugates were determined by liquid chromatography-mass spectrometry. RESULTS: The transfer percentage for antipyrine and BPA were 25.5 +/- 1.13% and 27.0 +/- 1.88%, respectively, and the transfer index for BPA was 1.1 +/- 0.09 after 180 minutes of perfusion. Only 3.2 +/- 1.6% of BPA in the fetal compartment was in the conjugated form. CONCLUSION: Bisphenol A at low environmentally relevant levels can transfer across the human placenta, mainly in active unconjugated form.

Synthesis and biological activity of azido analogues of 5,6-dimethylxanthenone-4-acetic acid for use in photoaffinity labeling.

5,6-Dimethylxanthenone-4-acetic acid (1) is scheduled for phase III clinical trials as a vascular disrupting agent. However, its biochemical receptor(s) have yet to be identified. In this report, the synthesis of azido analogues of 1 that could be used for photoaffinity labeling of proteins as an approach toward identifying its molecular targets is described. While 5-azidoxanthenone-4-acetic acid (2) and 5-azido-6-methylxantheone-4-acetic acid (3) were found to have biological activities similar to that of 1, 6-azido-5-methylxanthenone-4-acetic acid (4) was unstable and could not be evaluated. Both azido compounds 2 and 3 activated NF-kappaB, induced the production of tumor necrosis factor in cultured mouse splenocytes, and induced hemorrhagic necrosis of colon 38 tumors in mice. Photoreaction of lysates from spleen cells with tritiated 2 resulted in two radiolabeled protein bands at 50 and 14 kDa that could be competitively inhibited with cold 1 and cold 2. The azido compounds 2 and 3 exhibit all the requirements for use in photoaffinity labeling of potential receptor(s) for 1.