Characterization of natural killer and cytotoxic T-cell immune infiltrates in pancreatic ductal adenocarcinoma.

BACKGROUND AND OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor response to systemic therapies, including immunotherapy. Given the immunotherapeutic potential of natural killer (NK) cells, we evaluated intratumoral NK cell infiltrates along with cytotoxic T cells in PDAC to determine their association with patient outcomes. METHODS: We analyzed tumors from 93 PDAC patients treated from 2012 to 2020. Predictor variables included tumor-infiltrating lymphocytes (TILs), T-cell markers (CD3, CD8, CD45RO), NK marker (NKp46), and NK inhibitory marker (major histocompatibility complex class I [MHC-I]) by immunohistochemistry. Primary outcome variables were recurrence-free survival (RFS) and overall survival (OS). RESULTS: Mean TILs, CD3, and NKp46 scores were 1.3 ± 0.63, 20.6 ± 17.5, and 3.1 ± 3.9, respectively. Higher expression of CD3 and CD8 was associated with higher OS, whereas NK cell infiltration was not associated with either RFS or OS. There was a tight positive correlation between MHC-I expression and all T-cell markers, but not with NKp46. CONCLUSIONS: Overall NK cell infiltrates were low in PDAC and did not predict clinical outcomes, whereas T-cell infiltrates did. Further characterization of the immune infiltrate in PDAC, including inhibitory signals and suppressive cell types, may yield better biomarkers of prognosis and immune targeting in this refractory disease.

Visceral fat area and subcutaneous fat area as measures of body composition in soft tissue sarcoma.

BACKGROUND AND OBJECTIVES: Soft tissue sarcomas (STS) are a heterogenous group of malignancies of mesenchymal origin. Given recent data linking obesity as well as the pattern of fat distribution with cancer outcomes, we sought to investigate the association of visceral fat area (VFA) and subcutaneous fat area (SFA) with oncologic outcomes in patients with STS undergoing surgery. METHODS: We analyzed data from 88 patients with STS diagnosed from 2008 to 2022. Predictor variables included body mass index (BMI), VFA, and SFA. VFA and SFA were obtained from computed tomography of the abdomen and pelvis. Univariable and multivariable Cox regression analysis was used to analyze associations between predictor variables and overall survival and recurrence-free survival. RESULTS: Although BMI was closely correlated with VFA (r = 0.69, p < 0.0001) and SFA (r = 0.80, p < 0.0001), there was no significant association between high BMI, VFA or SFA, and worse oncologic outcomes. CONCLUSIONS: Although VFA and SFA are strongly correlated with BMI, we did not observe BMI nor imaging metrics of fat composition to be associated with worse oncologic outcomes. Further research is needed to elucidate any links between body fat content and metabolic or immune factors governing oncologic outcomes in STS.

Low-Dose Sorafenib Promotes Cancer Stem Cell Expansion and Accelerated Tumor Progression in Soft Tissue Sarcomas.

The cancer stem cell (CSC) hypothesis postulates that heterogeneous human cancers harbor a population of stem-like cells which are resistant to cytotoxic therapies, thus providing a reservoir of relapse following conventional therapies like chemotherapy and radiation (RT). CSCs have been observed in multiple human cancers, and their presence has been correlated with worse clinical outcomes. Here, we sought to evaluate the impact of drug dosing of the multi-tyrosine kinase inhibitor, sorafenib, on CSC and non-CSCs in soft tissue sarcoma (STS) models, hypothesizing differential effects of sorafenib based on dose and target cell population. In vitro, human cancer cell lines and primary STS from surgical specimens were exposed to escalating doses of sorafenib to determine cell viability and expression of CSC marker aldehyde dehydrogenase (ALDH). In vivo, ALDHbright CSCs were isolated, exposed to sorafenib, and xenograft growth and survival analyses were performed. We observed that sarcoma CSCs appear to paradoxically respond to the tyrosine kinase inhibitor sorafenib at low doses with increased proliferation and stem-like function of CSCs, whereas anti-viability effects dominated at higher doses. Importantly, STS patients receiving neoadjuvant sorafenib and RT on a clinical trial (NCT00864032) showed increased CSCs post therapy, and higher ALDH scores post therapy were associated with worse metastasis-free survival. These data suggest that low-dose sorafenib may promote the CSC phenotype in STS with clinically significant effects, including increased tumor growth and higher rates of metastasis formation in sarcoma patients.

Current Practices in Hepatic Artery Infusion (HAI) Chemotherapy: An International Survey of the HAI Consortium Research Network.

BACKGROUND: An increasing number of hepatic artery infusion (HAI) programs have been established worldwide. Practice patterns for this complex therapy across these programs have not been reported. This survey aimed to identify current practice patterns in HAI therapy with the long-term goal of defining best practices and performing prospective studies. METHODS: Using SurveyMonkeyTM, a 28-question survey assessing current practices in HAI was developed by 12 HAI Consortium Research Network (HCRN) surgical oncologists. Content analysis was used to code textual responses, and the frequency of categories was calculated. Scores for rank-order questions were generated by calculating average ranking for each answer choice. RESULTS: Thirty-six (72%) HCRN members responded to the survey. The most common intended initial indications for HAI at new programs were unresectable colorectal liver metastases (uCRLM; 100%) and unresectable intrahepatic cholangiocarcinoma (uIHC; 56%). Practice patterns evolved such that uCRLM (94%) and adjuvant therapy for CRLM (adjCRLM; 72%) have become the most common current indications for HAI at established centers. Referral patterns for pump placement differed between uCRLM and uIHC, with most patients referred while receiving second- and first-line therapy, respectively, with physicians preferring to evaluate patients for HAI while receiving first-line therapy for CRLM. Concern for extrahepatic disease was ranked as the most important factor when considering a patient for HAI. CONCLUSIONS: Indication and patient selection factors for HAI therapy are relatively uniform across most HCRN centers. The increasing use of adjuvant HAI therapy and overall consistency of practice patterns among HCRN centers provides a robust environment for prospective data collection and randomized clinical trials.

Sarcopenia and frailty as predictors of surgical morbidity and oncologic outcomes in retroperitoneal sarcoma.

BACKGROUND: Retroperitoneal sarcomas (RPS) are rare tumors for which surgical resection is the principal treatment. There is no established model to predict perioperative risks for RPS. We evaluated the association between preoperative sarcopenia, frailty, and hypoalbuminemia with surgical and oncological outcomes. METHODS: We performed a prospective cohort analysis of 65 RPS patients who underwent surgical resection. Sarcopenia was defined as Total Psoas Area Index ≤ 1st quintile by sex. Frailty was estimated using the modified frailty index (mFI). Logistic regression models were used to assess predictors of 30-day postoperative morbidity. The Kaplan-Meier method with log-rank test was utilized to assess factors associated with overall (OS) and recurrence-free survival (RFS). RESULT: Sarcopenia was associated with worse OS with a median of 54 compared with 158 months (p = 0.04), but no differences in RFS (p > 0.05). Hypoalbuminemia was associated with worse OS with a median of 72 compared with 158 months (p < 0.01). MFI scores were not associated with OS or RFS (p > 0.05). Sarcopenia, mFI, and hypoalbuminemia were not associated with postoperative morbidity (p > 0.05). CONCLUSION: This study suggests that sarcopenia may be utilized as a measure of overall fitness, rather than a cancer-specific risk, and the mFI is a poor predictive measure of outcomes in RPS.

Surgical and oncologic outcomes following arterial resection and reconstruction for advanced solid tumors.

BACKGROUND AND OBJECTIVES: Although arterial involvement for advanced tumors is rare, vascular resection may be indicated to achieve complete tumor resection. Given the potential morbidity of this approach, we sought to evaluate perioperative outcomes, vascular graft patency, and survival among patients undergoing tumor excision with en bloc arterial resection and reconstruction. METHODS: From 2010 to 2020, we identified nine patients with tumors encasing or extensively abutting major arterial structures for whom en bloc arterial resection and reconstruction was performed. RESULTS: Mean age was 53 ± 20 years, and 89% were females. Diagnoses were primary sarcomas (5), recurrent gynecologic carcinomas (3), and benign retroperitoneal fibrosis (1). Tumors involved the infrarenal aorta (2), iliac arteries (6), and superficial femoral artery (1). Three patients (33%) had severe perioperative morbidity (Grade III + ) with no mortality. At a median follow-up of 23 months, eight patients (89%) had primary graft patency, and five patients (56%) had no evidence of disease. CONCLUSIONS: Arterial resection and reconstruction as part of the multimodality treatment of regionally advanced tumors is associated with acceptable short- and long-term outcomes, including excellent graft patency. In appropriately selected patients, involvement of major arterial structures should not be viewed as a contraindication to attempted curative surgery.

Is minimally invasive surgery of lesions in the right superior segments of the liver justified? A multi-institutional study of 245 patients.

BACKGROUND: Controversy exists regarding the safety and feasibility of minimally invasive resection for lesions in segments 7 or 8. We compare outcomes of minimally invasive surgery (MIS) and Open parenchymal sparing liver resections at two high-volume centers. METHODS: From 2003 to 2016 we identified patients who underwent MIS or Open resections for lesions in segments 7 or 8 at two institutions (MSKCC and SGH). Outcomes were compared using univariate and multivariate analyses. RESULTS: Two-hundred and forty-five patients underwent resection of lesions in segments 7 or 8 (MIS 30% and Open 70%). Compared to the Open group, the MIS group had longer operative time (223 ± 88 vs 188 ± 72 minutes, P = .003), lower blood loss (297 ± 287 vs 448 ± 670 mL, P = .03), and shorter mean length of stay (5.2 ± 7.4 vs 8.3 ± 11.7 days, P < .001), which remained significant on multivariate analysis. No differences in Pringle time, rate of postoperative complications, or R0 resections were detected. CONCLUSIONS: With appropriately selected patients treated by experienced MIS hepatopancreatobiliary surgeons, MIS resection of segments 7 or 8 is safe with similar rates of complications and R0 resections, with significantly less blood loss and shorter length of stay.

Morbidity, mortality and temporal trends in the surgical management of retroperitoneal sarcoma: An ACS-NSQIP follow up analysis.

BACKGROUND: Calls for multivisceral resection (MVR) of retroperitoneal sarcoma (RPS) are increasing, although the risks and benefits remain controversial. We sought to analyze current 30-day morbidity and mortality rates, and trends in utilization of MVR in a national database. METHODS: Overall morbidity, severe morbidity, mortality rates, and temporal trends were analyzed utilizing the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). RESULTS: From 2012 to 2015, a total of 564 patients underwent RPS resection with 233 patients (41%) undergoing MVR. The MVR group had a higher rate of preoperative weight loss and larger tumors overall. When comparing MVR to non-MVR, there was no significant difference in overall morbidity (22% vs 17%, P = .13), severe morbidity (11% vs 8%, P = .18), or mortality (<1% vs 2%, P = .25). On multivariate analysis, MVR was not associated with increased overall morbidity or severe morbidity. Mortality rates were too low for meaningful statistical analysis. Annual rates of MVR ranged from 37% to 46% with no significant change over time (P = .47). RESULTS: Short-term morbidity and mortality rates after MVR for RPS remain acceptable, but rates of MVR show little change over time in NSQIP hospitals. Concerns about increased morbidity and mortality should not be viewed as a contraindication to wider implementation of MVR for RPS.

Consideration of a Novel Surgical Approach in the Management of Gastric Adenocarcinoma and Proximal Polyposis Syndrome.

Investigators at MSKCC highlight a novel surgical approach to manage GAPPS.

Preclinical evaluation and first-in-dog clinical trials of PBMC-expanded natural killer cells for adoptive immunotherapy in dogs with cancer.

BACKGROUND: Natural killer (NK) cells are cytotoxic cells capable of recognizing heterogeneous cancer targets without prior sensitization, making them promising prospects for use in cellular immunotherapy. Companion dogs develop spontaneous cancers in the context of an intact immune system, representing a valid cancer immunotherapy model. Previously, CD5 depletion of peripheral blood mononuclear cells (PBMCs) was used in dogs to isolate a CD5dim-expressing NK subset prior to co-culture with an irradiated feeder line, but this can limit the yield of the final NK product. This study aimed to assess NK activation, expansion, and preliminary clinical activity in first-in-dog clinical trials using a novel system with unmanipulated PBMCs to generate our NK cell product. METHODS: Starting populations of CD5-depleted cells and PBMCs from healthy beagle donors were co-cultured for 14 days, phenotype, cytotoxicity, and cytokine secretion were measured, and samples were sequenced using the 3'-Tag-RNA-Seq protocol. Co-cultured human PBMCs and NK-isolated cells were also sequenced for comparative analysis. In addition, two first-in-dog clinical trials were performed in dogs with melanoma and osteosarcoma using autologous and allogeneic NK cells, respectively, to establish safety and proof-of-concept of this manufacturing approach. RESULTS: Calculated cell counts, viability, killing, and cytokine secretion were equivalent or higher in expanded NK cells from canine PBMCs versus CD5-depleted cells, and immune phenotyping confirmed a CD3-NKp46+ product from PBMC-expanded cells at day 14. Transcriptomic analysis of expanded cell populations confirmed upregulation of NK activation genes and related pathways, and human NK cells using well-characterized NK markers closely mirrored canine gene expression patterns. Autologous and allogeneic PBMC-derived NK cells were successfully expanded for use in first-in-dog clinical trials, resulting in no serious adverse events and preliminary efficacy data. RNA sequencing of PBMCs from dogs receiving allogeneic NK transfer showed patient-unique gene signatures with NK gene expression trends in response to treatment. CONCLUSIONS: Overall, the use of unmanipulated PBMCs appears safe and potentially effective for canine NK immunotherapy with equivalent to superior results to CD5 depletion in NK expansion, activation, and cytotoxicity. Our preclinical and clinical data support further evaluation of this technique as a novel platform for optimizing NK immunotherapy in dogs.

Effect of ALDH1A1 and CD44 on Survival and Disease Recurrence in Patients With Osteosarcoma.

PURPOSE: Emerging evidence suggests that osteosarcoma stem cells (OSCs) may be responsible for tumor initiation propagation, recurrence, and resistance to therapy. We set out to evaluate the relationship between the abundance of ALDH1A1 and CD44-positive cells in biopsy and resection samples on disease recurrence and overall survival. METHODS: A retrospective review of 20 patients, including biopsy and resection samples, was performed at a comprehensive cancer center. Additionally, we queried the publicly available TARGET dataset of osteosarcoma patients. RESULTS: Neither the percentages of ALDH1A1-positive cells nor CD44-positive cells were significantly associated with overall mortality or disease recurrence in either biopsy or resection samples. Unlike our institutional data, overall survival was significantly correlated to higher ALDH1A1 expression in the TARGET dataset both in univariate and age-adjusted analyses. CONCLUSIONS: ADLH1 and CD44, potential markers of OSCs, were not found to be reliable clinical immunohistochemical prognostic markers for osteosarcoma patient survival, specifically disease-free survival. Osteosarcoma patients with high ALDH1A1 RNA expression showed improved overall survival in examining a national genomic database of osteosarcoma patients but again no association with disease-free survival. The potential of CD44 and ALDH1A1 as cellular-specific prognostic markers of survival, and as possible molecular targets, may be limited in osteosarcoma.

Watch and Wait in Rectal Cancer Patients with Residual Mucin on MRI following Neoadjuvant Therapy.

BACKGROUND: Neoadjuvant therapy (NAT) leads to a clinical complete response (cCR) in a significant proportion of patients with locally advanced rectal cancer (LARC), allowing for possible nonoperative management. The presence of mucin on MRI after NAT leads to uncertainty about residual disease and appropriateness of a watch-and-wait (WW) strategy in patients with no evidence of disease on proctoscopy (endoscopic cCR). METHODS: MRI reports for LARC patients seen between July 2016 and January 2020 at Memorial Sloan Kettering Cancer Center were queried for presence of mucin in the tumor bed on MRI following NAT. Clinicodemographic, pathologic, and outcome data were compiled and analyzed. RESULTS: Of 71 patients with mucin on post-treatment MRI, 20 had a cCR and 51 had abnormalities on endoscopy and/or physical exam. One patient with a cCR opted out of WW; thus, 19 patients (27%) entered WW and 52 patients (73%) were planned for surgery (Non-WW). Of the 19 WW patients, 15 (79%) have had no local regrowth with median follow-up of 50 months (range, 29-76 months), while 4 (21%) experienced regrowth between 9 and 29 months after neoadjuvant therapy. Of the 52 patients who were planned to have surgery (Non-WW), 49 underwent resection while 3 developed metastatic disease that precluded curative-intent surgery. Five (10%) of the 49 patients who underwent surgery, including the one with an endoscopic cCR, had a pathologic complete response. CONCLUSIONS: The presence of mucin after NAT for LARC does not preclude WW management in otherwise appropriate candidates who achieve an endoscopic cCR.

Regulation of human and mouse bystander T cell activation responses by PD-1.

Bystander activation of memory T cells occurs via cytokine signaling alone in the absence of T cell receptor (TCR) signaling and provides a means of amplifying T cell effector responses in an antigen-nonspecific manner. While the role of Programmed Cell Death Protein 1 (PD-1) on antigen-specific T cell responses is extensively characterized, its role in bystander T cell responses is less clear. We examined the role of the PD-1 pathway during human and mouse non-antigen-specific memory T cell bystander activation and observed that PD-1+ T cells demonstrated less activation and proliferation than activated PD-1- populations in vitro. Higher activation and proliferative responses were also observed in the PD-1- memory population in both mice and patients with cancer receiving high-dose IL-2, mirroring the in vitro phenotypes. This inhibitory effect of PD-1 could be reversed by PD-1 blockade in vivo or observed using memory T cells from PD-1-/- mice. Interestingly, increased activation through abrogation of PD-1 signaling in bystander-activated T cells also resulted in increased apoptosis due to activation-induced cell death (AICD) and eventual T cell loss in vivo. These results demonstrate that the PD-1/PD-Ligand 1 (PD-L1) pathway inhibited bystander-activated memory T cell responses but also protected cells from AICD.

Intratumoral NKp46+ natural killer cells are spatially distanced from T and MHC-I+ cells with prognostic implications in soft tissue sarcoma.

Introduction: Soft tissue sarcomas (STS) are rare, heterogenous malignancies with an unmet need for novel immunotherapies. Tumor infiltrating lymphocytes (TILs) have been linked with favorable outcomes in STS patients, though the contribution of natural killer (NK) cells and spatial relationships of TILs with MHC-I expressing cells lacks detailed characterization. Experimental design: Using archived and prospectively collected specimens, we evaluated intratumoral NK cells by immunohistochemistry (IHC), flow cytometry, and immunofluorescence (IF). We assessed spatial localization of NK and T cells by multiplex IF, analyzing the effects of MHC-I expression status on NK and T cell clustering. Results: Both intratumoral NKp46 and CD56dim expression were associated with significantly improved overall survival (P=0.05), while higher infiltrates of CD56bright NK cells predicted a worse prognosis (P=0.05). The presence of intratumoral NK cells was inversely proportional to CD3+ T cells. Spatial analyses showed NK cells preferentially clustering close to other NK cells with sparse CD3+ T and CD8+ T cells in range (P<0.0001). Additionally, CD3+ T and CD8+ T cells showed significantly greater co-localization with MHC-I+ cells, compared to NK cells (P<0.0001). After neoadjuvant radiotherapy, there was greater CD8 clustering, while after neoadjuvant chemotherapy, there was overall lower TIL clustering. Conclusion: Intratumoral NK cells are prognostic in STS and localize closer to MHC-I- cells than T cells. Although both NK and T cells are associated with improved survival in STS, their differential distribution in the TME based on MHC-I expression status may serve as a biomarker for improved immunotherapy treatment selection.

Human soft tissue sarcomas harbor an intratumoral viral microbiome which is linked with natural killer cell infiltrate and prognosis.

BACKGROUND: Groundbreaking studies have linked the gut microbiome with immune homeostasis and antitumor immune responses. Mounting evidence has also demonstrated an intratumoral microbiome, including in soft tissue sarcomas (STS), although detailed characterization of the STS intratumoral microbiome is limited. We sought to characterize the intratumoral microbiome in patients with STS undergoing preoperative radiotherapy and surgery, hypothesizing the presence of a distinct intratumoral microbiome with potentially clinically significant microbial signatures. METHODS: We prospectively obtained tumor and stool samples from adult patients with non-metastatic STS using a strict sterile collection protocol to minimize contamination. Metagenomic classification was used to estimate abundance using genus and species taxonomic levels across all classified organisms, and data were analyzed with respect to clinicopathologic factors. RESULTS: Fifteen patients were enrolled. Most tumors were located at an extremity (67%) and were histologic grade 3 (87%). 40% were well-differentiated/dedifferentiated liposarcoma histology. With a median follow-up of 24 months, 4 (27%) patients developed metastases, and 3 (20%) died. Despite overwhelming human DNA (>99%) intratumorally, we detected a small but consistent proportion of bacterial DNA (0.02-0.03%) in all tumors, including Proteobacteria, Bacteroidetes, and Firmicutes, as well as viral species. In the tumor microenvironment, we observed a strong positive correlation between viral relative abundance and natural killer (NK) infiltration, and higher NK infiltration was associated with superior metastasis-free and overall survival by immunohistochemical, flow cytometry, and multiplex immunofluorescence analyses. CONCLUSIONS: We prospectively demonstrate the presence of a distinct and measurable intratumoral microbiome in patients with STS at multiple time points. Our data suggest that the STS tumor microbiome has prognostic significance with viral relative abundance associated with NK infiltration and oncologic outcome. Additional studies are warranted to further assess the clinical impact of these findings.

Transcriptome Analysis of Tumor-Infiltrating Lymphocytes Identifies NK Cell Gene Signatures Associated With Lymphocyte Infiltration and Survival in Soft Tissue Sarcomas.

Purpose: Clinical successes using current T-cell based immunotherapies have been limited in soft tissue sarcomas (STS), while pre-clinical studies have shown evidence of natural killer (NK) cell activity. Since tumor immune infiltration, especially tumor-infiltrating lymphocytes, is associated with improved survival in most solid tumors, we sought to evaluate the gene expression profile of tumor and blood NK and T cells, as well as tumor cells, with the goal of identifying potential novel immune targets in STS. Experimental Design: Using fluorescence-activated cell sorting, we isolated blood and tumor-infiltrating CD3-CD56+ NK and CD3+ T cells and CD45- viable tumor cells from STS patients undergoing surgery. We then evaluated differential gene expression (DGE) of these purified populations with RNA sequencing analysis. To evaluate survival differences and validate primary DGE results, we also queried The Cancer Genome Atlas (TCGA) database to compare outcomes stratified by bulk gene expression. Results: Sorted intra-tumoral CD3+ T cells showed significant upregulation of established activating (CD137) and inhibitory genes (TIM-3) compared to circulating T cells. In contrast, intra-tumoral NK cells did not exhibit upregulation of canonical cytotoxic genes (IFNG, GZMB), but rather significant DGE in mitogen signaling (DUSP4) and metabolic function (SMPD3, SLC7A5). Tumors with higher NK and T cell infiltration exhibited significantly increased expression of the pro-inflammatory receptor TLR4 in sorted CD45- tumor cells. TCGA analysis revealed that tumors with high TLR4 expression (P = 0.03) and low expression of STMN1 involved in microtubule polymerization (P < 0.001) were associated with significantly improved survival. Conclusions: Unlike T cells, which demonstrate significant DGE consistent with upregulation of both activating and inhibiting receptors in tumor-infiltrating subsets, NK cells appear to have more stable gene expression between blood and tumor subsets, with alterations restricted primarily to metabolic pathways. Increased immune cell infiltration and improved survival were positively correlated with TLR4 expression and inversely correlated with STMN1 expression within tumors, suggesting possible novel therapeutic targets for immunotherapy in STS.

Inhaled recombinant human IL-15 in dogs with naturally occurring pulmonary metastases from osteosarcoma or melanoma: a phase 1 study of clinical activity and correlates of response.

PURPOSE: Although recombinant human interleukin-15 (rhIL-15) has generated much excitement as an immunotherapeutic agent for cancer, activity in human clinical trials has been modest to date, in part due to the risks of toxicity with significant dose escalation. Since pulmonary metastases are a major site of distant failure in human and dog cancers, we sought to investigate inhaled rhIL-15 in dogs with naturally occurring lung metastases from osteosarcoma (OSA) or melanoma. We hypothesized a favorable benefit/risk profile given the concentrated delivery to the lungs with decreased systemic exposure. EXPERIMENTAL DESIGN: We performed a phase I trial of inhaled rhIL-15 in dogs with gross pulmonary metastases using a traditional 3+3 cohort design. A starting dose of 10 µg twice daily × 14 days was used based on human, non-human primate, and murine studies. Safety, dose-limiting toxicities (DLT), and maximum tolerated dose (MTD) were the primary objectives, while response rates, progression-free and overall survival (OS), and pharmacokinetic and immune correlative analyses were secondary. RESULTS: From October 2018 to December 2020, we enrolled 21 dogs with 18 dogs reaching the 28-day response assessment to be evaluable. At dose level 5 (70 µg), we observed two DLTs, thereby establishing 50 µg twice daily × 14 days as the MTD and recommended phase 2 dose. Among 18 evaluable dogs, we observed one complete response >1 year, one partial response with resolution of multiple target lesions, and five stable disease for an overall clinical benefit rate of 39%. Plasma rhIL-15 quantitation revealed detectable and sustained rhIL-15 concentrations between 1-hour and 6 hour postnebulization. Decreased pretreatment lymphocyte counts were significantly associated with clinical benefit. Cytotoxicity assays of banked peripheral blood mononuclear cells revealed significant increases in peak cytotoxicity against canine melanoma and OSA targets that correlated with OS. CONCLUSIONS: In this first-in-dog clinical trial of inhaled rhIL-15 in dogs with advanced metastatic disease, we observed promising clinical activity when administered as a monotherapy for only 14 days. These data have significant clinical and biological implications for both dogs and humans with refractory lung metastases and support exploration of combinatorial therapies using inhaled rhIL-15.

Natural Killer and T Cell Infiltration in Canine Osteosarcoma: Clinical Implications and Translational Relevance.

Metastatic osteosarcoma has a bleak prognosis in both humans and dogs, and there have been minimal therapeutic advances in recent decades to improve outcomes. Naturally occurring osteosarcoma in dogs is shown to be a highly suitable model for human osteosarcoma, and limited data suggest the similarities between species extend into immune responses to cancer. Studies show that immune infiltrates in canine osteosarcoma resemble those of human osteosarcoma, and the analysis of tumor immune constituents as predictors of therapeutic response is a promising direction for future research. Additionally, clinical studies in dogs have piloted the use of NK transfer to treat osteosarcoma and can serve as valuable precursors to clinical trials in humans. Cytotoxic lymphocytes in dogs and humans with osteosarcoma have increased activation and exhaustion markers within tumors compared with blood. Accordingly, NK and T cells have complex interactions among cancer cells and other immune cells, which can lead to changes in pathways that work both for and against the tumor. Studies focused on NK and T cell interactions within the tumor microenvironment can open the door to targeted therapies, such as checkpoint inhibitors. Specifically, PD-1/PD-L1 checkpoint expression is conserved across tumors in both species, but further characterization of PD-L1 in canine osteosarcoma is needed to assess its prognostic significance compared with humans. Ultimately, a comparative understanding of T and NK cells in the osteosarcoma tumor microenvironment in both dogs and humans can be a platform for translational studies that improve outcomes in both dogs and humans with this frequently aggressive disease.