Abstract 5269: Imaging the tumor microenvironment in rectal cancer: Decline in tumor blood flow (BF) during neoadjuvant treatment predicts excellent outcome

Introduction: A watch-and-wait strategy for rectal cancer patients may possibly omit surgery after neoadjuvant treatment. To optimally stratify patients for such strategy, reliable and preferably non-invasive biomarkers that repeatedly can assess neoadjuvant therapy response are needed. Recognizing the importance of the tumor microenvironment, we investigated a less explored imaging marker assessing tumor BF for its potential to predict overall survival (OS).

Methods: 24 rectal cancer patients given curative-intent neoadjuvant radiotherapy (RT) underwent a multi-echo dynamic magnetic resonance imaging (MRI) sequence with gadolinium contrast for estimation of tumor BF before either 25x2 Gy (n=18) with concomitant chemotherapy or 5x5 Gy (n=6). 4-7 weeks post-RT the MRI was repeated. Baseline blood samples were analyzed for lactate dehydrogenase (LDH) and angiopoietin-2 (ANGPT-2). Tumor volumes were measured before and after RT. After the subsequent surgery, ypT scoring assessed tumor RT response. Cox regression for OS analysis and t-test for group comparisons were performed.

Results: 7 patients were non-survivors and the median follow-up for survivors was 55 months (range, 44-60). The change in tumor BF (ΔBF) during neoadjuvant RT was identified as a significant marker of OS (Table). Tumor stage and volume were not significant. All patients with more than 20% decline in BF were survivors. Separating cases in two groups based on ΔBF revealed that patients with increase or a low decrease had higher baseline levels of LDH (p = 0.032) and ANGPT-2 (p = 0.028).

Discussion: MRI-assessed tumor ΔBF during neoadjuvant treatment is a significant predictor of OS in rectal cancer patients, making ΔBF a potential biomarker for treatment stratification in a watch-and-wait strategy. Blood LDH and ANGPT-2 indicate that non-responding tumors may have a hypoxic microenvironment insusceptible to RT.

Parameter Hazard ratio for impaired OS p-value Tumor stage 1.08 [0.40-2.95] 0.88 ypT score of the surgical specimen 1.54 [0.76-3.12] 0.23 RT fractionation (25x2 Gy versus 5x5 Gy) 2.24 [0.50-9.90] 0.29 Baseline BF 0.96 [0.92-1.00] 0.05 Post-RT BF 1.02 [1.00-1.04] 0.11 ΔBF 1.03 [1.01-1.05] 0.01 Baseline tumor volume 1.01 [0.99-1.04] 0.43 Post-RT tumor volume 1.01 [0.98-1.05] 0.42 Δtumor volume 1.03 [0.99-1.07] 0.15

Citation Format: Kine M. Bakke, Sebastian Meltzer, Endre Grøvik, Anne Negård, Stein H. Holmedal, Lars G. Lyckander, Arne E. Færden, Atle Bjørnerud, Kjell-Inge Gjesdal, Anne H. Ree, Kathrine R. Redalen. Imaging the tumor microenvironment in rectal cancer: Decline in tumor blood flow (BF) during neoadjuvant treatment predicts excellent outcome [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 5269.

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.

Abstract 4514: Low release of exosomal miR-663a from hypoxic tumor cells and poor tumor response to neoadjuvant radiotherapy in rectal cancer patients

Introduction: Hypoxia is an important hallmark of the tumor microenvironment and contributes significantly to radiotherapy resistance in solid tumors. Exosomes are nanosized vesicles actively released from tumor cells, and recent studies support their central role in the aggravated biology caused by tumor hypoxia through their miRNA cargo. In this study, we aimed to characterize miRNAs of exosomes from hypoxic colorectal cancer (CRC) cell lines and investigate these miRNAs in circulating exosomes from rectal cancer patients with poor response to neoadjuvant radiotherapy.

Methods: Five CRC cell lines were cultured in RPMI-1640 medium supplemented with 1% bovine serum albumin under normoxia (21% O2) or hypoxia (0.2% O2) for 24 hours. Exosomes were isolated from conditioned media by differential ultracentrifugation, and integrity and size were determined by cryo-electron microscopy and NanoSight tracking analysis and further characterized by Western blot and flow cytometry analyses. In a prospective biomarker study, plasma samples were collected from 29 patients with rectal cancer at the time of diagnosis, and histologic tumor response (tumor regression grade, TRG) to neoadjuvant radiotherapy was evaluated. Exosomes were isolated from plasma using the miRCURY™ Exosome Isolation Kit (Exiqon). Expression profiling of exosomal miRNAs of the CRC cell lines and the patients’ plasma samples was conducted using the miRCURY LNA™ Universal RT microRNA PCR Human panel I (Exiqon). Data normalization was performed based on global array mean.

Results: Normoxic and hypoxic CRC cells released vesicles, 30-150 nm in size, that expressed proteins known to be enriched in exosomes (CD9, CD63, CD81, Alix) and with absence of markers of the endoplasmic reticulum (GRP78, Calnexin) and the Golgi apparatus (GM130). Exosomes from the CRC cell lines harbored strong cell line-specific miRNA profiles; however, when comparing the hypoxic cell lines collectively with the normoxic counterparts, four exosomal miRNAs (miR-195-5p, miR-423-3p, miR-622, miR-663a) were significantly down-regulated by hypoxia. Of these, circulating exosomal miR-663a was lower (p = 0.033) in rectal cancer patients with poor tumor response (TRG 2-3) to neoadjuvant radiotherapy.

Conclusion: Vesicles released from CRC cell lines were characterized as exosomes carrying miRNAs that were retrieved in the circulation of rectal cancer patients, where low level of exosomal miR-663a at the time of diagnosis was associated with poor tumor response to neoadjuvant radiotherapy. These findings suggest that repressed release of miR-663a from tumor cells into the circulation may be a marker of radiotherapy resistance caused by tumor hypoxia. The results are currently under validation in an independent patient cohort. Trial registration: NCT01816607

Citation Format: Tonje Bjørnetrø, Karianne R. Handeland, Sebastian Meltzer, Rampradeep Samiappan, Lars G. Lyckander, Caroline Jegerschöld, Linda Sønstevold, Nirujah S. Thusyanthan, Kathrine R. Redalen, Anne H. Ree. Low release of exosomal miR-663a from hypoxic tumor cells and poor tumor response to neoadjuvant radiotherapy in rectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4514. doi:10.1158/1538-7445.AM2017-4514

Evaluation of disease activity in IBD at the time of diagnosis by the use of clinical, biochemical, and fecal markers

OBJECTIVE

The present population based adult cohort was part of a new prospective study of patients with inflammatory bowel disease (IBD) in South-Eastern Norway, the Inflammatory Bowel South-Eastern Norway II study, investigating disease characteristics in an attempt to improve our knowledge regarding factors related to early clinical phenotype and disease activity.

MATERIAL AND METHODS

Patients suspected to have IBD on the basis of predefined symptoms, including abdominal pain, diarrhea, and/or blood in stool for more than 10 days were examined at the local hospital. Colonoscopy with biopsies was performed and blood and stool samples were taken.

RESULTS

In ulcerative colitis (UC) patients, the median Simple Clinical Colitis Activity Index (SCCAI) was 4 (range 0-10) in mild and 6 (range 0-14) in patients with moderate or severe endoscopic activity of inflammation (p = 0.002). The calprotectin concentration in feces was significantly related to the SCCAI (p = 0.034) and the Mayo endoscopic subscore (p = 0.031). There was a significant association between the C-reactive protein (CRP) value, leucocytes and thrombocytes and the SCCAI, but only leucocytes were significantly associated with the Mayo endoscopic subscore. In Crohn's disease (CD) patients, there was no statistical significant association between the Harvey-Bradshaw Index (HBI) and the endoscopic grade of mucosal inflammation (p = 0.8). The calprotectin concentration in feces was significantly related to the endoscopic activity score (p = 0.004), but not to the HBI (p = 0.5). HBI was significantly related to the CRP value (p = 0.047) and thrombocytes (p = 0.03).

CONCLUSIONS

In UC, both biochemical and fecal markers are related to disease activity and extent of disease, whereas in CD, the fecal calprotectin concentration is a reliable marker of mucosal affection, but not for systemic disease activity.

A characterization in childhood inflammatory bowel disease, a new population-based inception cohort from South-Eastern Norway, 2005-07, showing increased incidence in Crohn's disease

OBJECTIVE

Owing to rising incidence rates in inflammatory bowel disease (IBD), there has been increased interest in causal relationships in pediatric disease. The present population-based inception cohort was recruited in the Oslo area from 2005 to 2007, with the aim of conducting a detailed characterization of treatment-naive patients at diagnosis.

MATERIAL AND METHODS

After an invitation was extended to all general practitioners in the catchment area, patients aged <18 years with suspected IBD were diagnosed by proximal and distal endoscopy, MRI, demographic, clinical, and histological and molecular characteristics. Symptomatic non-IBD patients served as controls.

RESULTS

Of 100 pediatric patients, 62 had IBD (39 Crohn's disease (CD), 19 ulcerative colitis (UC), 4 IBD unclassified (IBDU)) and 38 other diseases. Median age at diagnosis for IBD was 13.1 years (56.4% males), median symptom duration 6 months, and 69% L3 (Vienna classification). With 195,000 children aged <18 years in the catchment area, the incidence rate of IBD per 100,000/years inhabitants was 10.9 (6.8 for CD, 3.6 for UC, and 0.6 IBDU) and for those aged <16 years (178,500) the incidence rate was 10.6. The higher NOD2 allele frequency among children may partly contribute to the increase.

CONCLUSIONS

The results indicate a marked rise in the incidence of CD in contrast to no increase in UC in South-Eastern Norway, compared with the figures from the last 15 years. Time from onset of symptoms to diagnosis still represents a challenge for early characterization in IBD.