Immune suppression in tumor-draining lymph nodes

What is a sentinal lymph node

First tumour draining LN/ The first lymph node that drains lymph from the primary tumor site.

DC subset	what function?
cDC1
cDC2
Migratory DCs (migDCs)
Plasmacytoid DCs (pDCs)
Monocyte-derived DCs (moDCs)

DC subset	Main function
cDC1	Cross-presentation of antigens to CD8+ T cells
cDC2	Antigen presentation to CD4+ T cells
Migratory DCs (migDCs)	Travel to lymph nodes and present antigen to T cells
Plasmacytoid DCs (pDCs)	Produce type I interferons
Monocyte-derived DCs (moDCs)	Promote inflammatory responses; can also be influenced by tumor-derived tolerogenic signals

What are the 5 key activities of DC?

• Migration: DCs must reach the lymph node draining the tumor.

• Antigen presentation: MHC molecules present antigen-derived peptides to T cells.

• Co-stimulation: DCs provide additional signals needed for effective T-cell activation.

• Effector-activating cytokines: for example, IL-12 and type I interferons.

• Memory-inducing cytokines: the slide identifies IL-1β as an example.

Roles of migratory cDC1 and resident (in LN) cDC1

• Migratory cDC1 transport tumor antigens from the tumor to the lymph node.

• These DCs stimulate CD8+ T cells.

• The activated CD8+ T cells produce XCL1, which attracts lymph-node-resident cDC1 through XCR1.

• Migratory cDC1 transfer tumor antigen to resident cDC1.

• Resident cDC1 are particularly potent at stimulating the anti-tumor CD8+ T-cell response.

Where are the LN important in the mellman cancer immunity cycle

Antigen presentation and T cell priming

How to identify the sentinel LN

Can be identified using the triple-technique (radioactive tracer/blue-dye tracer/hand-held detector to localize the radioactive LNo

• Injecting a radioactive tracer near the primary tumor.

• Injecting blue dye at the tumor site.

• Identifying and removing the lymph node that is radioactive (“hot”) and blue.

Progenitor-exhausted T cells are not equivalent to terminally exhausted T cells.

Progenitor-exhausted cells retain the capacity for self-renewal and further differentiation.

How cancer cells can regulate immune cell behavior / Tumor cells can manipulate immune cells through four main mechanisms.

• Through secreted factors (cytokines, chemokines, growth factors)

• Through extracellular vesicles

• By changing the metabolic environment through oxygen and nutrient consumption

• Via direct cell-cell contact

• Tumor cells secrete suppressive factor: cytokines, chemokines, growth factors and extracellular vesicles

• These factors can suppress locally, in the tumor, but also drain to the SLN

• DC development, migration and activation are hampered by many of

  these factors

• These factors induce Treg formation, which hampers T cell and NK cell functions in tumor-draining LNs

• This can form a metastatic niche within the SLN and downstream LNs

Tumor-derived exosomes/extracellular vesicles can suppress the SLN environment and promote tumor metastasis. How

• Tumor cells can secrete exosomes (or extracellular vesicles – (EVs))

• These EVs can contain suppressive surface molecules (like PD-L1 or TGFbeta) that can change immune cells

• EVs can also contain mRNAs or miRNAs that can alter immune cell behavior and make them suppressive

• This can create a metastatic niche in the SLN

Tumor-secreted cytokines, like IL-10, IL-6 and PGE2 hamper DC activation. How

• Myeloid cell have a high plasticity

• Their phenotype, and subsequent functioning, can be altered by suppressive cytokines

• The STAT3 and p38 pathways when activated, hamper DC development and maturation.

• This suppression of DC development can result downstream in Treg induction, anergic/suppressed T cells, promotion of angiogenesis, promotion of tumor invasion

Immune status in tumor- draining LNs at least is influenced by the following anatomical, histological or immunological factors:

Factor	Type	Main implication
Proximity to the tumor	Anatomical	Determines exposure to tumor-derived signals
Size of the primary tumor	Histological / tumor-related	Can influence migratory DC activation
Tumor-secreted suppressive factors	Immunological	Can impair DC maturation and alter immune-cell function
Tumor metastasis in the lymph node	Histological	Can disrupt resident DCs and favour suppressive populations

3 types of TME based on T cell infiltation

Type 1 IFN is a crucial player in antitumour response. List its functions

Functions of IFN 1 as a tumour progressor when the immune balance is lost

Who secretes type 1 IFN

PDC . Plasmacytoid DC in LN

GM-CSF

CpG

list their function

GM-CSF — recruits and activates conventional DCs

CpG — stimulates TLR9

CpG is a ligand for Toll-like receptor 9 (TLR9). Plasmacytoid DCs can respond to TLR9 stimulation by producing large amounts of type I interferons.

How can we restore the working of the SLN?

locally injecting immune activating compounds (CpG ± GM-CSF)

anti-CTLA-4 checkpoint inhibition

• Early-stage disease: DC activation may be an appropriate strategy to strengthen the initiation of anti-tumor immunity.

• Later-stage disease: combining DC activation with checkpoint inhibition may be needed to address both inadequate immune priming and established immune suppression.

The SLN is important to initiate an anti-tumor immune response, but tumors suppress their functioning

To overcome immune suppression in tumor-draining LNs we aim to:

• Activate LNR-cDC and –pDC in SLN/tumor-draining LNs using stimuli that will promote a type I interferon response and skew towards a Th1 T cell response. At the same time we want to reduce Treg frequencies.

• Combine this treatment with checkpoint inhibitors (anti-CTLA4, anti-PD(L)1, and/or others) to counteract tumor- and immune activation induced T cell inhibition in the LNs and the tumor.

• Deliver these agents locally to reduce systemic toxicity, while providing systemic protection.