Article 2: Targeting CXCL12/CXCR4 signaling with oncolytic virotherapy disrupts tumor vasculature and inhibits breast cancer metastases Flashcards
what is the goal of this paper?
combine VV oncolysis with dismantling of vasculature via preventing CXCL12/CXCR4 to prevent metastasis
VV mediated + CXCR4-A-mediated –> direct oncolysis + block metastasis –> tumor clearance
what are VV’s modifications for specificity in this paper?
- vaccinia growth factor (VGF) has homology to epidermal growth factor –> paracrine mediator, primes neighboring cells for incoming viruses
- delthaVGF
- deltaTK + CXCR4 antagonist
why add a CXCR4 antagonist?
CXCR4 is expressed on many types of solid tumors, including breast, prostate, brain, colon and lung
CXCL12 = cytokine; CXCR4 = receptor
why target CXCR4/CXCL12?
- CXCL12 can induce CXCR4+ cancer cells to secrete VEGF and IL-6 to promote angiogenesis in tumors
- CXCL12 can recruit endothelial progenitor cells to sires of neovascularization in tumors to promote angiogenesis
what can be expressed by an OV to stop CXCL12/CXCR4?
CTCE-9908 is a 17aa peptide analog of CXCL12 that functions as a CXCR4 antagonist by blocking the interaction of the CXCR4 receptor with CXCL12
dimerized (helps binding) sequence of the disordred N-term region of CXCL12-A and was designed to block the CXCR4 receptor
how to express the dimerized antagonist from a gene?
use the antibody Fc region –> transgene: CXCR4-A-Fc controlled under the TK promoter
Q1: what is the effectiveness of soluble and virally derived CXCR4-A-mFc in inhibiting tumor growth
method?
- induced tumor growth in immunodeficient mice by injecting 4T1 breast cancer tumor cells
- controlled for initial tumor size of 150mm3
- intravenous injection of soluble CXCR4-A-mFc for 7 days vs single injection of OVV-CXCR4-A-mFc
- 7 day treatment of soluble antagonist used to match 7 days of viral replication
- measured volume of tumor after treatment
Q1: what is the effectiveness of soluble and virally derived CXCR4-A-mFc in inhibiting tumor growth
results and conclusions?
results
- soluble antagonist inhibited tumor growth for two weeks, but growth returned to similar rates as the controls
- virally derived antagonist inhibits tumor growth for the first 3 weeks and results in continues diminsed rates of growth compared to controls
- reduction in tumor growth by OVV-EGFP
conclusions
- OVV-CXCR4-A-mFc seems more effective at reducing tumor growth than its soluble counterpart
Q2: are the differences in tumor growth reduction between soluble and virally derived CXCR4-A-mFc due to differences in their intratumoral concentrations?
method?
- collect tumor tissue and serum (how much is getting out of the tumor environment?)
- used ELISA to detect concentration of CXCR4-A-hFc present in each sample
- measured samples on days 4 and 8
Q2: are the differences in tumor growth reduction between soluble and virally derived CXCR4-A-mFc due to differences in their intratumoral concentrations?
results and conclusions?
results
- OVV-CXCR4-A-hFc is present in higher concentrations in the tumor but not the sera compared to the soluble antagonist
conclusion
- OVV-CXCR4-A-mFC’s increased ability to reduce tumor growth correlates with its higher intratumoral concerntrations than soluble antagonist
Q3: can the oncolytic virus CXCR4-A-mFc reduce tumor vasculature?
experimental and control groups?
groups
- PBS
- OVV + GFP
- OVV + CXCR4-A
Q3.1: does vascular disruption caused by the treatments affect tumor perfusion?
methods, results and conclusions?
method
- inject fluorescent beads intravenously into mice –> collect tumors and fix –> fluorescence microscopy
results
- PBS: high blood flow to periphery and core
- OVV-EGFP: high blood flow to peripher and less to core
- OVV-CXCR-A-mFc: less blood flow to periphery and core
conclusion
- OVV-CXCR4-A-mFc decreased perfusion in both the tumor periphery and core
Q3.2: can the oncolytic virus CXCR4-A-mFc reduce markers of microvessel denisty and cell proliferation?
method, results, conclusion?
method
- IHC of tumor: CD31 (contributes to tumor invasion, neasured by microvessel density; MVD) and Ki-67 (marker for proliferation, measured by number of proliferating cells)
results
- PBS: high MVD in periphery and core; high Ki67 in periphery and core
- OVV + EGFP: high MVD in periphery, low in core; high Ki67 in periphery, low in core
- OVV-CXCR4-A-mFc: low MVD in periphery and core; low Ki67 in periphery and core
conclusions
- OVV-CXCR4-A-mFc correlates witht the most consistent reduction in tumor vasculature and proliferating cells in core and periphery
Q3.3: what effects does OVV-CXCR4-A-mFc have on intratumoral expression of CXCL12 and VEGF, and recruitment of circulating endothelial cells (CEPs) and neutrophils/G-MDSCs?
methods, results and conclusion?
methods
- ELISA for CXCL12 and VEGF in tumor
- FCM for CEPs and neutrophils/G-MDSCs
results
- oVV-CXCR4-A-mFc was most effective at reducing CXCL12 and VEGF in the tumor
- OVV-CXCR-A-mFc was msot effective at reducing CEPs and neutrophils/G-MDSCs in tumor
- virus alone tend to promote inflammatory neutrophils/G-MDSCs
conclusion
- OVV-CXCR4-A-mFc reduces intratumoral expression of CXCL12 and VEGF, and reduces recruitment of CEPs and neutrophils/G-MDSCs
Q4: how effective is OVV-CXCR4-A-mFc at reducing metastatic burden?
methods/rationale, results and conclusion?
methods
- 4T1 is highly metastatic –> produces metastatic colonies in the lungs at early stages (within 10 days)
- metastatic growth in control and treatment groups were monitored by in vivo bioluminescence
- lung metastases were assessed by histology on formalin-fixed and HE stained sections
results
- OVV-CXCR4-A-mFc has the lowest amount of metastatic colonies in the lungs
conclusion
- OVV-EGFP and OVV-CXCR4-A-mFc decrease metastatic burden
