Transient TCR-based T cell therapy in a patient with advanced treatment-resistant MSI-high colorectal cancer

We previously demonstrated the antitumor effectiveness of transiently T cell receptor (TCR)-redirected T cells recognizing a frameshift mutation in transforming growth factor beta receptor 2. We here describe a clinical protocol using mRNA TCR-modified T cells to treat a patient with progressive, treatment-resistant metastatic microsatellite instability-high (MSI-H) colorectal cancer. Following 12 escalating doses of autologous T cells electroporated with in-vitro-transcribed Radium-1 TCR mRNA, we assessed T cell cytotoxicity, phenotype, and cytokine production. Tumor markers and growth on computed tomography scans were evaluated and immune cell tumor infiltrate at diagnosis assessed. At diagnosis, tumor-infiltrating CD8+ T cells had minimal expression of exhaustion markers, except for PD-1. Injected Radium-1 T cells were mainly naive and effector memory T cells with low expression of exhaustion markers, except for TIGIT. We confirmed cytotoxicity of transfected Radium-1 T cells against target cells and found key cytokines involved in tumor metastasis, growth, and angiogenesis to fluctuate during treatment. The treatment was well tolerated, and despite his advanced cancer, the patient obtained a stable disease with 6 months survival post-treatment. We conclude that treatment of metastatic MSI-H colorectal cancer with autologous T cells electroporated with Radium-1 TCR mRNA is feasible, safe, and well tolerated and that it warrants further investigation in a phase 1/2 study.

The mitochondrial DNA constitution shaping T-cell immunity in patients with rectal cancer at high risk of metastatic progression

PURPOSE

A significant percentage of colorectal cancer patients proceeds to metastatic disease. We hypothesised that mitochondrial DNA (mtDNA) polymorphisms, generated by the high mtDNA mutation rate of energy-demanding clonal immune cell expansions and assessable in peripheral blood, reflect how efficiently systemic immunity impedes metastasis.

PATIENTS AND METHODS

We studied 44 rectal cancer patients from a population-based prospective biomarker study, given curative-intent neoadjuvant radiation and radical surgery for high-risk tumour stage and followed for metastatic failure. Blood specimens were sampled at the time of diagnosis and analysed for the full-length mtDNA sequence, composition of immune cell subpopulations and damaged serum mtDNA.

RESULTS

Whole blood total mtDNA variant number above the median value for the study cohort, coexisting with an mtDNA non-H haplogroup, was representative for the mtDNA of circulating immune cells and associated with low risk of a metastatic event. Abundant mtDNA variants correlated with proliferating helper T cells and cytotoxic effector T cells in the circulation. Patients without metastatic progression had high relative levels of circulating tumour-targeting effector T cells and, of note, the naïve (LAG-3+) helper T-cell population, with the proportion of LAG-3+ cells inversely correlating with cell-free damaged mtDNA in serum known to cause antagonising inflammation.

CONCLUSION

Numerous mtDNA polymorphisms in peripheral blood reflected clonal expansion of circulating helper and cytotoxic T-cell populations in patients without metastatic failure. The statistical associations suggested that patient's constitutional mtDNA manifests the helper T-cell capacity to mount immunity that controls metastatic susceptibility.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01816607; registration date: 22 March 2013.

Peptide vaccine targeting mutated GNAS: a potential novel treatment for pseudomyxoma peritonei

Background

Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer with no efficacious treatment options in non-resectable and recurrent cases. Otherwise, rare activating mutations in the GNAS oncogene are remarkably frequent in PMP and the mutated gene product, guanine nucleotide-binding protein α subunit (Gsα), is a potential tumor neoantigen, presenting an opportunity for targeting by a therapeutic cancer vaccine.

Methods

Tumor and blood samples were collected from 25 patients undergoing surgery for PMP (NCT02073500). GNAS mutation analysis was performed by next-generation targeted sequencing or digital droplet PCR. Responses to stimulation with Gsα mutated (point mutations R201H and R201C) 30 mer peptides were analyzed in peripheral blood T cells derived from patients with PMP and healthy donors. Fresh PMP tumor samples were analyzed by mass cytometry using a panel of 35 extracellular markers, and cellular subpopulations were clustered and visualized using the visual stochastic network embedding analysis tool.

Results

GNAS mutations were detected in 22/25 tumor samples (88%; R201H and R201C mutations detected in 16 and 6 cases, respectively). Strong T cell proliferation against Gsα mutated peptides was observed in 18/24 patients with PMP. Mass cytometry analysis of tumor revealed infiltration of CD3 +T cells in most samples, with variable CD4+:CD8 + ratios. A large proportion of T cells expressed immune checkpoint molecules, in particular programmed death receptor-1 and T cell immunoreceptor with Ig and ITIM, indicating that these T cells were antigen experienced.

Conclusion

These findings point to the existence of a pre-existing immunity in patients with PMP towards mutated Gsα, which has been insufficient to control tumor growth, possibly because of inhibition of antitumor T cells by upregulation of immune checkpoint molecules. The results form a rationale for exploring peptide vaccination with Gsα peptides in combination with immune checkpoint inhibiton as a possible curative treatment for PMP and other GNAS mutated cancers.

Circulating mitochondrial DNA (mtDNA) variants to predict metastatic progression of rectal cancer

e16132

Background: High rates of systemic failure after curative-intent therapy in locally advanced rectal cancer (LARC) call for new diagnostic tools to improve risk-based treatment stratification. We hypothesized that blood mtDNA polymorphisms, generated by the high mtDNA mutation rate when the mitochondrial biogenesis is mobilized during clonal immune cell activation, correlate with systemic immune control of LARC dissemination and thus can be used as diagnostic marker. Methods: 41 LARC patients given neoadjuvant (chemo)radiotherapy had DNA extracted from whole blood (WB) sampled at the time of diagnosis, for high-throughput full-length mtDNA sequencing followed by annotation of mtDNA variants using the curated reference genome (mitomap.org). The composition of peripheral blood mononuclear cell (PBMC) subpopulations was analyzed by high-dimensional single-cell mass cytometry. Metastatic events were recorded over 24-60 months of follow-up after completion of the multimodal treatment. Results: The total number of WB-mtDNA variants was strikingly different across the study cases but without correlation to patient’s age, body mass index, or metformin use, which may affect mitochondrial function, or to the disease extension at presentation or the local tumor response to the neoadjuvant therapy. All patients had microsatellite-stable tumor. The higher the number of variants in MT-RNR2, encoding one of the two ribosomal subunits of mitochondria, the better distant metastasis-free survival (DMFS). For each patient, two MT-RNR2 sites were homoplasmic for either the normal or a deletion (3105AC > A, 3106CN > C) variant, categorizing the patients into two groups that comprised the same cases for both mtDNA sites. Nine of a total of 10 DMFS events occurred during the 18 first months of follow-up in one of the patient groups ( n = 23). The single event in the other group ( n = 18) appeared in a patient who had declined primary tumor surgery. In the former group, a low number of variants in the ribosomal subunit MT-RNR1 identified all patients who had metastatic progression. These patients had reduced PBMC frequency of CD8+ (cytolytic) T cells that were positive for CXCR4 ( p = 0.001), a chemokine receptor that promotes their homing to tumor sites. Conclusions: The WB-ribosomal mtDNA polymorphisms reflected systemic immune cells endowed with cytolytic and tumor-homing properties. The actual mtDNA variants were single-base alterations and might thus be analyzed by PCR and developed as a feasible assay for metastatic risk assessment in rectal cancer. Clinical trial information: 01816607 .