[68Ga]Ga-Pentixafor PET/CT imaging for in vivo CXCR4 receptor mapping in different lung cancer histologic sub-types: correlation with quantitative receptors' density by immunochemistry techniques

PURPOSE

In vivo CXCR4 receptor quantification in different lung cancer (LC) sub-types using [⁶⁸Ga]Ga-Pentixafor PET/CT and to study correlation with quantitative CXCR4 receptors' tissue density by immunochemistry analyses.

METHODS

[⁶⁸Ga]Ga-Pentixafor PET/CT imaging was performed prospectively in 94 (77 M: 17F, mean age 60.1 ± 10.1 years) LC patients. CXCR4 receptors' expression on lung mass in all the patients was estimated by immunohistochemistry (IHC) and fluorescence-activated cell sorting (FACS) analyses. SUV_max on PET, intensity score on IHC, and mean fluorescence index (MFI) on FACS analyses were measured.

RESULTS

A total of 75/94 (79.8%) cases had non-small cell lung cancer (NSCLC), 14 (14.9%) had small cell lung cancer (SCLC), and 5 (5.3%) had lung neuroendocrine neoplasm (NEN). All LC types showed increased CXCR4 expression on PET (SUV_max) and FACS (MFI). However, both these parameters (mean SUV_max = 10.3 ± 5.0; mean MFI = 349.0 ± 99.0) were significantly (p = 0.005) higher in SCLC as compared to those in NSCLC and lung NEN. The mean SUV_max in adenocarcinoma (n = 16) was 8.0 ± 1.9 which was significantly (p = 0.003) higher than in squamous cell carcinoma (n = 54; 6.2 ± 2.1) and in not-otherwise specified (NOS) sub-types (n = 5; 5.8 ± 1.5) of NSCLC. A significant correlation (r = 0.697; p = 001) was seen between SUV_max and MFI values in squamous cell NSCLC as well as in NSCLC adenocarcinoma (r = 0.538, p = 0.031) which supports the specific in vivo uptake of [⁶⁸Ga]Ga-Pentixafor by CXCR4 receptors. However, this correlation was not significant in SCLC (r = 0.435, p = 0.121) and NEN (r = 0.747, p = 0.147) which may be due to the small sample size. [⁶⁸Ga]Ga-Pentixafor PET/CT provided good sensitivity (85.7%) and specificity (78.1%) for differentiating SCLC from NSCLC (ROC cutoff SUV_max = 7.2). This technique presented similar sensitivity (87.5%) and specificity (71.4%) (ROC cutoff SUV_max = 6.7) for differentiating adenocarcinoma and squamous cell variants of NSCLC.

CONCLUSION

The high sensitivity and specificity of [⁶⁸Ga]Ga-Pentixafor PET/CT for in vivo targeting of CXCR4 receptors in lung cancer can thus be used effectively for the response assessment and development of CXCR4-based radioligand therapies in LC.

Abstract 1330: Role of ENPP1 mediated extracellular cGAMP hydrolysis in cancer metastasis and immune evasion

Chromosome instability (CIN) promotes metastasis through sustained tumor-cell autonomous response to cytosolic DNA. Chromosome mis-segregation engenders the formation of micronuclei, which upon rupture chronically activates the cGAS-STING DNA sensing pathway. Tumor cGAS recognizes cytosolic DNA to generate cGAMP, a potent immune-stimulatory molecule that is readily exported into the extracellular space to enforce a type 1 IFN-mediated anti-tumor response in a host STING dependent manner. However, it is unclear how highly aggressive, unstable tumors have evolved to co-opt this chronic inflammatory signaling to drive tumorigenic behaviors and immune evasion. Here, we show that ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) may drive tumor metastasis through degradation of extracellular cGAMP. Using RNA sequencing of isogenic tumors, we uncovered a link between ENPP1 and CIN. We leveraged syngeneic mouse models to demonstrate that genetic perturbation of tumor ENPP1 and overexpression of a catalytically inactive ENPP1 mutant suppress metastasis. Furthermore, loss of ENPP1 increases tumor immune infiltration, reduces extracellular adenosine, and enhances response to immune checkpoint blockade in a manner dependent on tumor cGAS and host STING. In line with these findings, ENPP1 expression correlates with immune suppression in human cancers. These results suggest that ENPP1-mediated hydrolysis of cGAMP may facilitate metastasis through evasion of immune surveillance, perhaps in part through cGAMP breakdown into immune-suppressive adenosine, in which the contributions of tumor and host adenosine can be further explored. Taken together, our study demonstrates how ENPP1-mediated hydrolysis of cGAMP can transform an otherwise inflammatory pathway into an immune-suppressive mechanism to promote tumor progression and metastasis.

Citation Format: John Young Ho Kwon, Jun Li, Mercedes Duran, Ninjit Dhanota, Samuel Bakhoum. Role of ENPP1 mediated extracellular cGAMP hydrolysis in cancer metastasis and immune evasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1330.

Metastasis and Immune Evasion from Extracellular cGAMP Hydrolysis

Cytosolic DNA is characteristic of chromosomally unstable metastatic cancer cells, resulting in constitutive activation of the cGAS-STING innate immune pathway. How tumors co-opt inflammatory signaling while evading immune surveillance remains unknown. Here, we show that the ectonucleotidase ENPP1 promotes metastasis by selectively degrading extracellular cGAMP, an immune-stimulatory metabolite whose breakdown products include the immune suppressor adenosine. ENPP1 loss suppresses metastasis, restores tumor immune infiltration, and potentiates response to immune checkpoint blockade in a manner dependent on tumor cGAS and host STING. Conversely, overexpression of wild-type ENPP1, but not an enzymatically weakened mutant, promotes migration and metastasis, in part through the generation of extracellular adenosine, and renders otherwise sensitive tumors completely resistant to immunotherapy. In human cancers, ENPP1 expression correlates with reduced immune cell infiltration, increased metastasis, and resistance to anti-PD-1/PD-L1 treatment. Thus, cGAMP hydrolysis by ENPP1 enables chromosomally unstable tumors to transmute cGAS activation into an immune-suppressive pathway. SIGNIFICANCE: Chromosomal instability promotes metastasis by generating chronic tumor inflammation. ENPP1 facilitates metastasis and enables tumor cells to tolerate inflammation by hydrolyzing the immunotransmitter cGAMP, preventing its transfer from cancer cells to immune cells.This article is highlighted in the In This Issue feature, p. 995.