I’m presenting results from a large single cell RNA sequencing study on tumour cells and immune cells from patients with MGUS, smouldering myeloma and overt myeloma. We’re profiling a total of 877 samples, 533 bone marrow and peripheral blood specimens and 365 individuals. In a large fraction of individuals we are profiling both tumour cells and immune cells to really be able to look at both tumour cells and immune cells at the same time and enable integrative analysis. In total we have profiled 6 million cells, this is truly a massive number, we are running into limitations of software and Google cloud machinery.

We’ve been able to identify novel immune biomarkers of disease progression such as an increase in granzyme B expressing cytotoxic T-cells with disease progression. These are the more mature, more differentiated cytotoxic T-cells that you typically want to fight against tumour cells and yet in myeloma we see that the more of these cells you have the higher your risk of progression. In fact, by looking at single cell RNA sequencing data of tumour cells and quantifying the proliferative index of the tumour, we also see that the more granzyme B expressing cytotoxic T-cells you have the more aggressive the tumour biology, the higher the proliferative index of the tumour.

This is counterintuitive. Again, you would expect that these are the cells that help you fight against the tumour but in our case we also observed significant changes in immune cell functionality. This, we think, explains this counterintuitive observation. We think that the T-cells, although expanding, clonally expanding too we see, are actually dysfunctional.

In addition to that, we observe a significant depletion of cytokine expressing myeloid cells, both monocytes and dendritic cells. This is interesting too because looking at cell types, less relying on hard clustering methods and more trying to quantify the true spectrum that a cell phenotype really is, we are able to find cytokine programmes that increase with progression within myeloid cells and those would be the pro-inflammatory programmes that recruit neutrophils, for example, and cytokine programmes that decrease with progression. Those typically reflect the hypoxic conditions of the bone marrow microenvironment.

Another fascinating finding is that increased interferon signalling is associated with progression and, again, this may be counterintuitive to some people – interferon is thought to help strengthen some of these immune cell responses against tumours. What’s unique about myeloma is it’s a tumour of the immune system and so chances are it’s also helping the tumour cells in certain ways. So what we see is that interferon signalling is active in both immune cells and tumour cells and we are able to validate that in external cohorts and show that truly the higher the interferon signalling in your bone marrow the higher your risk of progression.

Lastly, we look at the T-cell receptor repertoire and we see that its diversity decreases with progression so you have more clonal T-cell expansion with progression. This may make sense intuitively because patients with myeloma are also older compared to patients with MGUS and aging itself is associated with clonal T-cell expansions. But we show that the effect of the disease is actually independent of the effect of chronological age. So we can think of this as accelerated immune aging that’s conferred by the acquisition of this myeloma clone. We were able to show that patients who have more clonal T-cell expansion are at high risk of progression and also show, by doing bulk TCR sequencing this time, in roughly 100 patients in the COMPASS cohort show that it also confers inferior response to therapy and ultimately leads to shorter overall survival.

What impact could these findings have?

The hope is that the study, by virtue of its truly massive size, and it hasn’t been done before, the hope is that it’s going to be transformative in the way we think about risk stratification. A lot of the things we see have been observed in smaller scale before but it’s important to be able to show that these hold true when you really torture them with these more sensitive technologies, be able to validate them across multiple cohorts. What I envision this study would hopefully do for us in myeloma is maybe encourage us to do more immune profiling for risk stratification, rely on immune profiling for therapy selection as well. I think it’s important to do that in a tumour like myeloma. It’s a tumour of the immune system and a tumour that’s often treated with immunomodulatory therapy or immunotherapy and yet we don’t look at the immune system. I hope that studies like this one will actually help cause that paradigm shift and we start doing routine immune profiling for our patients.

Also we’ve shown before that immune profiling can really help you monitor response to therapy. So overall this is what I hope the study will bring forward.