Hsp90 is a molecular chaperone that protects proteins, including oncogenic signaling complexes, from proteolytic degradation. PU-H71 is a next-generation Hsp90 inhibitor that preferentially targets ...the functionally distinct pool of Hsp90 present in tumor cells. Tumors that are driven by the MYC oncoprotein may be particularly sensitive to PU-H71 due to the essential role of Hsp90 in the epichaperome, which maintains the malignant phenotype in the setting of MYC. Burkitt lymphoma (BL) is an aggressive B-cell lymphoma characterized by MYC dysregulation. In this study, we evaluated Hsp90 as a potential therapeutic target in BL. We found that primary BL tumors overexpress Hsp90 and that Hsp90 inhibition has antitumor activity
and
, including potent activity in a patient-derived xenograft model of BL. To evaluate the targets of PU-H71 in BL, we performed high-affinity capture followed by proteomic analysis using mass spectrometry. We found that Hsp90 inhibition targets multiple components of PI3K/AKT/mTOR signaling, highlighting the importance of this pathway in BL. Finally, we found that the anti-lymphoma activity of PU-H71 is synergistic with dual PI3K/mTOR inhibition
and
Overall, this work provides support for Hsp90 as a therapeutic target in BL and suggests the potential for combination therapy with PU-H71 and inhibitors of PI3K/mTOR.
.
Despite advances in T-cell immunotherapy against Epstein-Barr virus (EBV)-infected lymphomas that express the full EBV latency III program, a critical barrier has been that most EBV+ lymphomas ...express the latency I program, in which the single Epstein-Barr nuclear antigen (EBNA1) is produced. EBNA1 is poorly immunogenic, enabling tumors to evade immune responses. Using a high-throughput screen, we identified decitabine as a potent inducer of immunogenic EBV antigens, including LMP1, EBNA2, and EBNA3C. Induction occurs at low doses and persists after removal of decitabine. Decitabine treatment of latency I EBV+ Burkitt lymphoma (BL) sensitized cells to lysis by EBV-specific cytotoxic T cells (EBV-CTLs). In latency I BL xenografts, decitabine followed by EBV-CTLs results in T-cell homing to tumors and inhibition of tumor growth. Collectively, these results identify key epigenetic factors required for latency restriction and highlight a novel therapeutic approach to sensitize EBV+ lymphomas to immunotherapy.
•A high-throughput screen identified hypomethylating agents as inducers of latency III viral antigens in latency I EBV+ BL.•Induction of latency III antigens in BL sensitizes resistant tumors to T-cell–mediated lysis with EBV-specific cytotoxic T lymphocytes.
Display omitted
The sparse vascularity of pancreatic ductal adenocarcinoma (PDAC) presents a mystery: What prevents this aggressive malignancy from undergoing neoangiogenesis to counteract hypoxia and better support ...growth? An incidental finding from prior work on paracrine communication between malignant PDAC cells and fibroblasts revealed that inhibition of the Hedgehog (HH) pathway partially relieved angiosuppression, increasing tumor vascularity through unknown mechanisms. Initial efforts to study this phenotype were hindered by difficulties replicating the complex interactions of multiple cell types in vitro. Here we identify a cascade of paracrine signals between multiple cell types that act sequentially to suppress angiogenesis in PDAC. Malignant epithelial cells promote HH signaling in fibroblasts, leading to inhibition of noncanonical WNT signaling in fibroblasts and epithelial cells, thereby limiting VEGFR2-dependent activation of endothelial hypersprouting. This cascade was elucidated using human and murine PDAC explant models, which effectively retain the complex cellular interactions of native tumor tissues.
We present a key mechanism of tumor angiosuppression, a process that sculpts the physiologic, cellular, and metabolic environment of PDAC. We further present a computational and experimental framework for the dissection of complex signaling cascades that propagate among multiple cell types in the tissue environment. This article is featured in Selected Articles from This Issue, p. 201.
Aerobic exercise is associated with decreased cancer incidence and cancer-associated mortality. However, little is known about the effects of exercise on pancreatic ductal adenocarcinoma (PDA), a ...disease for which current therapeutic options are limited. Herein, we show that aerobic exercise reduces PDA tumor growth, by modulating systemic and intra-tumoral immunity. Mechanistically, exercise promotes immune mobilization and accumulation of tumor-infiltrating IL15Rα+ CD8 T cells, which are responsible for the tumor-protective effects. In clinical samples, an exercise-dependent increase of intra-tumoral CD8 T cells is also observed. Underscoring the translational potential of the interleukin (IL)-15/IL-15Rα axis, IL-15 super-agonist (NIZ985) treatment attenuates tumor growth, prolongs survival, and enhances sensitivity to chemotherapy. Finally, exercise or NIZ985 both sensitize pancreatic tumors to αPD-1, with improved anti-tumor and survival benefits. Collectively, our findings highlight the therapeutic potential of an exercise-oncology axis and identify IL-15 activation as a promising treatment strategy for this deadly disease.
Display omitted
•Aerobic exercise restricts pancreatic tumor growth by enhancing anti-tumor immunity•The anti-tumor effects of aerobic exercise are driven by IL-15Rα+ CD8 T cells•Pharmacological activation of IL-15/IL-15Rα promotes a durable anti-tumor response•Aerobic exercise and IL-15 activation sensitize pancreatic tumors to α-PD-1 therapy
Kurz. et al. discover that aerobic exercise slows pancreatic cancer growth in mice through activation of the immune system, particularly CD8+ T cells. The beneficial effects of exercise can be mimicked by treatment with an IL-15 super-agonist, NIZ985. Exercise or NIZ985 both improve the responsiveness of murine pancreatic tumors to immune- and non-immune- based therapeutics.
Although nucleoside analogues have been used effectively in the clinic for the treatment of a wide range of hematological malignancies, lack of response to currently available nucleoside analogues ...and drug resistance limit their utility. A rare but highly aggressive cancer is primary effusion lymphoma (PEL). Through high throughput screening, we have discovered a novel nucleoside analog, called 6-ethylthioinosine (6-ETI) as a potent and selective inhibitor of PEL, with little activity in other lymphomas tested. PEL is a rare B-cell non-Hodgkin's lymphoma characterized by lymphomatous effusions in body cavities. It is associated with Kaposi's sarcoma herpesvirus (KSHV/HHV-8) infection and occurs mainly in immunocompromised patients. PEL is known to frequently be resistant to conventional chemotherapy (CHOP and EPOCH) resulting in poor prognosis and a rather incurable disease. Our studies demonstrated that 6-ETI is a pro-drug activated by adenosine kinase (ADK), an enzyme that is overexpressed in PEL cell lines and primary PEL specimens, as well as other plasma cell malignancies, including plasmablastic lymphoma (PBL) and multiple myeloma (MM). The latter is also responsive to 6-ETI in vitro and in mouse models. 6-ETI induces S phase arrest and inhibits DNA synthesis. RNA sequencing of in vitro generated PEL resistant clones and CRISPR knock out of ADK (ADK KO), respectively, indicated that mutations or loss of expression of ADK renders cells resistant to treatment. This data demonstrates that ADK expression can be used as a predictive biomarker of response to 6-ETI, which can help identify which patients are more likely to respond to this treatment.
We investigated which pathways are differentially regulated in sensitive and resistant cells to better delineate the mechanism of action of 6-ETI and to design effective combinatorial regimens and prevent resistance. We found that drug sensitivity was associated with AMPK activation and inhibition of PI3K/mTOR/p70S6K signaling. Little is known about the function of ADK in plasma cell neoplasms. Knock-out of this protein in PEL, or use of ADK chemical inhibitors, do not affect their viability. Thus, we used ADK KO cell lines to examine the role of ADK in these tumors and to determine if cells undergo adaptations that may contribute to 6-ETI resistance and represent potential vulnerabilities to combat it. We performed metabolic and transcriptomic profiling of wild type (WT) (6-ETI sensitive) and ADK KO (6-ETI resistant) cells to achieve a comprehensive assessment of all the metabolic perturbations and gene expression changes induced by knocking out ADK. We also treated these cells with 6-ETI to examine the effects in sensitive and resistant cells. This integrated analysis revealed that 6-ETI depletes sensitive PEL cells of their nucleotide pools accompanied by the downregulation of several genes in purine and pyrimidine biosynthesis pathways. We found that adenine supplementation rescues sensitive PEL cells from 6-ETI induced cytotoxicity, reverses p70S6K inhibition and restores DNA synthesis suggesting that purine metabolism is a critical mediator of 6-ETI induced cytotoxicity. Using seahorse bioenergetic assay, we show that ADK KO resistant cells have impaired mitochondrial respiration indicating that ADK plays a critical role in mitochondrial bioenergetics. Metabolic profiling of these ADK KO resistant cells showed that these cells have elevated levels of de novo pyrimidine metabolic intermediates. Metabolic flux through de novo pyrimidine is controlled by the rate limiting enzyme CAD. The activity of CAD is regulated by ribosomal protein S6 Kinase 1(S6K1) by phosphorylation at its (Ser1859) site. Using western blotting, we observed a striking increase of phosphorylation of CAD at its S6K1 site (Ser1859) in ADK KO cells compared to WT cells.
This is the first to date study that characterizes the role of ADK in lymphomas. Our data indicates that ADK KO cells have undergone metabolic reprogramming to upregulate de novo pyrimidine biosynthesis and p70S6K signaling. Moreover, we found that 6-ETI synergizes with the pan PI3K inhibitor BKM120 highlighting nucleotide metabolism and PI3K/mTOR signaling as key therapeutic vulnerabilities targeted by this novel nucleoside analog.
No relevant conflicts of interest to declare.
Broad-spectrum RAS inhibition has the potential to benefit roughly a quarter of human patients with cancer whose tumours are driven by RAS mutations
. RMC-7977 is a highly selective inhibitor of the ...active GTP-bound forms of KRAS, HRAS and NRAS, with affinity for both mutant and wild-type variants
. More than 90% of cases of human pancreatic ductal adenocarcinoma (PDAC) are driven by activating mutations in KRAS
. Here we assessed the therapeutic potential of RMC-7977 in a comprehensive range of PDAC models. We observed broad and pronounced anti-tumour activity across models following direct RAS inhibition at exposures that were well-tolerated in vivo. Pharmacological analyses revealed divergent responses to RMC-7977 in tumour versus normal tissues. Treated tumours exhibited waves of apoptosis along with sustained proliferative arrest, whereas normal tissues underwent only transient decreases in proliferation, with no evidence of apoptosis. In the autochthonous KPC mouse model, RMC-7977 treatment resulted in a profound extension of survival followed by on-treatment relapse. Analysis of relapsed tumours identified Myc copy number gain as a prevalent candidate resistance mechanism, which could be overcome by combinatorial TEAD inhibition in vitro. Together, these data establish a strong preclinical rationale for the use of broad-spectrum RAS-GTP inhibition in the setting of PDAC and identify a promising candidate combination therapeutic regimen to overcome monotherapy resistance.
Abstract More than 90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS. RMC-7977 is a potent inhibitor of GTP-bound RAS proteins (RAS(ON)), including ...both wild type and mutant variants of KRAS, NRAS, and HRAS. The related investigational agent, RMC-6236, is a first-in-class, potent, orally bioavailable, RASMULTI(ON) inhibitor currently in Phase 1/1b clinical trials (NCT05379985). We performed preclinical studies in a range of models of PDAC, including the highly chemoresistant K-rasLSL.G12D/+, p53LSL.R172H/+, Pdx1Cretg/+ (KPC) genetically engineered mouse. RMC-7977 exhibited broad anti-tumor activity at tolerable doses, provoking radiographic responses in KPC pancreatic tumors and extending overall survival by 3-fold, the largest response observed yet in this model. RMC-7977 dosing produced a metronomic effect on RAS signaling in tumor and normal tissues, with full pathway inhibition at 4 hours post treatment that was restored by 24 hours. This pattern yielded tumor-selective effects on apoptosis and proliferation, consistent with RAS oncogene addition in PDAC. To understand the dynamic response of malignant cells following RAS-GTP inhibition, we did single cell RNA sequencing on KPC pancreatic tumors treated with RMC-7977 or vehicle at multiple timepoints. Using the ARACNe and VIPER algorithms Maroling., et al. 2006; Alvarez., et al. 2016, we performed regulatory network analysis on the expression profiles of >210,000 cells to calculate the activities of >5000 transcriptional regulatory proteins per cell. Additionally, we assessed the impact of treatment on malignant cell subtypes as previously identified by our team based on their sets of hyperactivated developmental transcription factors Laise., et al. 2022. As expected, RAS pathway transcription factors, such as FOS and JUN, were repressed relative to controls in malignant cells by 4 hours after treatment with RMC-7977. However, at 24 hours, responses varied by cellular subtype: well-differentiated Gastrointestinal Lineage State (GLS) cells had restored MAPK activity, while poorly differentiated Morphogenic State (MOS) cells were still inactivated. Strikingly, we found that after one week of treatment (in actively regressing tumors, representing a state of residual disease), nearly all malignant cells had assumed the GLS state. Acquisition of resistance after weeks or months of treatment was associated with a restored diversity of malignant cell states, suggesting that the GLS state serves as a regulatory “safe harbor” in which residual malignant cells can undergo evolution and adaptation. Mechanistically, we found that RAS pathway signaling directly activates transcriptional regulators that drive the MOS state, elucidating an early adaptive response to RAS-GTP inhibition that enables residual cells to survive treatment prior to development of acquired resistance. Citation Format: Lorenzo Tomassoni, Urszula N. Wasko, Alvaro C. Garcia, Tanner C. Dalton, Pasquale Laise, Stephen A. Sastra, Carmine F. Palermo, Andrea Califano, Kenneth P. Olive. Adaptive heterogeneity enables the survival of residual malignant PDAC cells in response to RAS-GTP inhibition abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3874.
Abstract Immunotherapy has revolutionized clinical care for many patients, but some cancers, such as pancreatic ductal adenocarcinoma (PDAC) remain stubbornly resistant. Local immunosuppression (LIS) ...is one of the striking hallmarks of PDAC due to the combined effects of multiple different immunosuppressive cell types in the tumor microenvironment (TME). There is great need for an increased understanding of the cellular crosstalk within tumors to understand how stromal cells coordinate in their suppression of immune responses. Oncogenic KRAS activation in tumor cells promotes the invasion and proliferation of tumor-supporting stromal cells, while excluding cancer-targeted cytotoxic T cells. Prior attempts to reverse LIS in PDAC by targeting individual stromal cell populations have been unsuccessful, alluding to the contributions of multiple distinct cell types. Here we examine the interactions of cancer-associated fibroblasts (CAFs) and myeloid-derived suppressor cells (MDSCs) and how they coordinate to suppress immune responses in the PDAC TME. We interrogate PDAC stromal cell biology by using targeted therapies to perturb various cell populations both in vivo using genetically engineered mouse models, and ex vivo using PDAC tumor explants. Explants are short-term slice cultures that enable experimental study of intact tumor sections with a full complement of cell types. Importantly, PDAC explants maintain their histopathological architecture and cellular diversity over time. This medium-throughput platform allows for testing of multiple drugs and mechanistic hypotheses in the native PDAC TME. We show in preliminary data that Smoothened inhibition (SMOi) decreases the proliferation and activity of myCAFs, but provokes the expansion of CD11b-positive myeloid cells in vivo. Thus, we hypothesize that LIS in PDAC is maintained by a balance between myCAFs and myeloid cells, preventing effective T cell invasion. Single cell RNA-seq data comparing ctrl vs. SMOi-treated murine PDAC elucidates stromal subpopulations involved in the LIS phenotype and guides the identification of myeloid subtypes emerging after SMOi. Strikingly, we demonstrated that simultaneous SMOi and targeting myeloid cells via anti-Gr1 or CCR1 inhibition significantly elevates cytotoxic T cell numbers within the TME. We are currently investigating whether the activity of these T cells may be further potentiated through combination with immunomodulatory agents. By testing various treatment combination in the same TME, we will identify the best synergistic effects for future immunotherapy approaches in human PDAC. In summary, we are elucidating the complex mechanism behind LIS in PDAC by employing our novel explant culture system alongside in vivo studies. We aim to develop a translatable regimen to neutralize LIS, reactivating the cytotoxic T cells in the tumor periphery to invade, proliferate, and attack cancer cells. Citation Format: Marie C. Hasselluhn, Dafydd Thomas, Lukas Vlahos, Alvaro Curiel-Garcia, Amanda R. Decker-Farrell, Tanner C. Dalton, Stephen A. Sastra, Carmine F. Palermo, Andrea Califano, Kenneth P. Olive. Disrupting local immunosuppression by combined myCAF/myeloid targeting in pancreatic cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1596.
Abstract More than 90% of human pancreatic ductal adenocarcinoma (PDAC) cases are driven by activating mutations in KRAS. RMC-7977 is a potent inhibitor of GTP-bound RAS proteins (RAS(ON), including ...both wild type and mutant variants of KRAS, NRAS, and HRAS. The related investigational agent, RMC-6236, is a first-in-class, potent, orally bioavailable, RASMULTI(ON) inhibitor currently in Phase 1/1b clinical trials (NCT05379985). We performed preclinical studies in a range of models of PDAC, including the highly chemoresistant K-rasLSL.G12D/+, p53LSL.R172H/+, Pdx1Cretg/+ (KPC) genetically engineered mouse. RMC-7977 exhibited broad anti-tumor activity at tolerable doses, provoking radiographic responses in KPC pancreatic tumors and extending overall survival by 3-fold, the largest response observed yet in this model. RMC-7977 dosing produced a metronomic effect on RAS signaling in tumor and normal tissues. This yielded tumor-selective effects on apoptosis and proliferation, consistent with RAS oncogene addition in PDAC. PDAC tumors are characterized by an expansive stroma that harbors multiple subtypes of cancer associated fibroblasts (CAFs) that manufacture a fibrotic, inflammatory extracellular matrix. CAF proliferation is driven by signals emanating from the malignant epithelial cells, such as Sonic Hedgehog (SHH), a secreted ligand that drives downstream Hedgehog pathway signaling in myofibroblastic CAFs (myCAFs). To understand the impact of RAS-GTP inhibition on paracrine signaling to CAFs in PDAC, To understand the dynamic responses of malignant epithelial cells following GTP-RAS inhibition, we performed single cell RNA sequencing (scRNAseq) on KPC pancreatic tumors treated with RMC-7977 or vehicle at multiple timepoints. Using the ARACNe and VIPER algorithms, we performed single cell regulatory network analysis on the expression profiles of >210,000 cells to calculate the activities of thousands of transcriptional regulatory protein in each cell. We found that the RAS-GTP inhibition blocked SHH expression in malignant epithelial cells, resulting in loss of downstream Hh pathway activity in CAFs within 24 hours of treatment. By one week of treatment, myCAFs were significantly depleted whereas inflammatory CAFs (iCAFs) were significantly accumulated. Strikingly, CAF heterogeneity was restored in KPC pancreatic tumors that acquired resistance to RMC-7977, despite continued suppression of Hedgehog pathway signaling. Consistent with prior studies of Smoothened inhibitors, the depletion of myCAFs from RAS-GTP inhibition was associated with the rapid opening and hypersprouting of intra-tumoral blood vessels. Ongoing studies using the mutant-selective KRASG12D inhibitor RM-044 should discriminate between direct effects of wild type RAS inhibition in CAFs versus the paracrine consequences of mutant RAS inhibition in malignant epithelial cells. Citation Format: Marie Hasselluhn, Lorenzo Tomassoni, Urszula Wasko, Alvaro Curiel-Garcia, Tanner Dalton, Steve A. Sastra, Carmine Palermo, Andrea Califano, Kenneth P. Olive. RAS-GTP inhibition modulates Hedgehog signaling, suppressing myCAFs and promoting iCAFs in pancreatic ductal adenocarcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1578.
PDF
