Tumor Adaptive Resistance Research Articles

Novel Cocktail Therapy Based on a Nanocarrier with an Efficient Transcytosis Property Reverses the Dynamically Deteriorating Tumor Microenvironment for Enhanced Immunotherapy.

The immune checkpoint blockade (ICB) faces a low response rate in clinical cancer treatment. Chemotherapy could enhance the response rate of the ICB, but patients would suffer from side effects. The off-target toxicity could be reduced by loading the chemotherapeutic agent through nanocarriers. Therefore, we developed a polymeric carrier for doxorubicin (DOX) loading to form DOX nanoparticles (DOX NPs), which were spatiotemporally responsive to the tumor microenvironment (TME). DOX NPs had an efficient transcytosis property for deep tumor infiltration and sustained drug release ability. Unfortunately, a binary therapy of DOX NPs and ICB induces tumor adaptive resistance and causes dynamic deterioration of the TME. We propose for the first time that TGF-β1 is a major cause of tumor adaptive resistance and developed an immune cocktail therapy containing DOX NPs, ICB, and TGF-β1 gene silencing nanoparticles. This therapy successfully overcame tumor adaptive resistance by reversing the immunosuppressive TME and achieved enhanced tumor treatment efficiency.

The oncoprotein BCL6 enables solid tumor cells to evade genotoxic stress

Genotoxic agents remain the mainstay of cancer treatment. Unfortunately, the clinical benefits are often countered by a rapid tumor adaptive response. Here, we report that the oncoprotein B cell lymphoma 6 (BCL6) is a core component that confers solid tumor adaptive resistance to genotoxic stress. Multiple genotoxic agents promoted BCL6 transactivation, which was positively correlated with a weakened therapeutic efficacy and a worse clinical outcome. Mechanistically, we discovered that treatment with the genotoxic agent etoposide led to the transcriptional reprogramming of multiple pro-inflammatory cytokines, among which the interferon-α and interferon-γ responses were substantially enriched in resistant cells. Our results further revealed that the activation of interferon/signal transducer and activator of transcription 1 axis directly upregulated BCL6 expression. The increased expression of BCL6 further repressed the tumor suppressor PTEN and consequently enabled resistant cancer cell survival. Accordingly, targeted inhibition of BCL6 remarkably enhanced etoposide-triggered DNA damage and apoptosis both in vitro and in vivo. Our findings highlight the importance of BCL6 signaling in conquering solid tumor tolerance to genotoxic stress, further establishing a rationale for a combined approach with genotoxic agents and BCL6-targeted therapy.

Cholesterol Regulates the Tumor Adaptive Resistance to MAPK Pathway Inhibition.

Although targeted MAPK pathway inhibition has achieved remarkable patient responses in many cancers, the development of resistance has remained a critical challenge. Adaptive tumor response underlies the drug resistance. Furthermore, such bypass mechanisms often lead to the activation of many pro-survival kinases, which complicates the rational design of combination therapies. Here, we performed global tyrosine phosphoproteomic (pTyr) analyses and demonstrated that targeted MAPK signaling inhibition in melanoma leads to a profound remodeling of the pTyr proteome. Intriguingly, altered cholesterol metabolism might drive, in a coordinated fashion, the activation of these kinases. Indeed, we found an accumulation of intracellular cholesterol in melanoma cells (with BRAFV600E mutations) and non-small cell lung cancer cells (with KRASG12C mutations) treated with MAPK and KRASG12C inhibitors, respectively. Importantly, depletion of cholesterol not only prevents the feedback activation of pTyr signaling but also enhances the cytotoxic effects of MAPK pathway inhibitors, both in vitro and in vivo. Together, our findings suggest that cholesterol contributes to the tumor adaptive response upon targeted MAPK pathway inhibitors. These results also suggest that MAPK pathway inhibitors could be combined with cholesterol-lowering agents to achieve a more complete and durable response in tumors with hyperactive MAPK signaling.

Cyclin B1/CDK1-regulated mitochondrial bioenergetics in cell cycle progression and tumor resistance

A mammalian cell houses two genomes located separately in the nucleus and mitochondria. During evolution, communications and adaptations between these two genomes occur extensively to achieve and sustain homeostasis for cellular functions and regeneration. Mitochondria provide the major cellular energy and contribute to gene regulation in the nucleus, whereas more than 98% of mitochondrial proteins are encoded by the nuclear genome. Such two-way signaling traffic presents an orchestrated dynamic between energy metabolism and consumption in cells. Recent reports have elucidated the way how mitochondrial bioenergetics synchronizes with the energy consumption for cell cycle progression mediated by cyclin B1/CDK1 as the communicator. This review is to recapitulate cyclin B1/CDK1 mediated mitochondrial activities in cell cycle progression and stress response as well as its potential link to reprogram energy metabolism in tumor adaptive resistance. Cyclin B1/CDK1-mediated mitochondrial bioenergetics is applied as an example to show how mitochondria could timely sense the cellular fuel demand and then coordinate ATP output. Such nucleus-mitochondria oscillation may play key roles in the flexible bioenergetics required for tumor cell survival and compromising the efficacy of anti-cancer therapy. Further deciphering the cyclin B1/CDK1-controlled mitochondrial metabolism may invent effect targets to treat resistant cancers.

Abstract 5603: Melanoma PD1 expression is upregulated by MAPK inhibitors leading to an immune-independent synergism with anti-PD1 antibodies

Abstract Background Antibodies blocking the inhibitory checkpoint PD1, expressed by T lymphocytes, and kinase inhibitors of BRAF and MEK (MAPKi) are mainstays of current treatment for patients with metastatic melanoma. Mouse models point towards a synergistic antitumor activity of anti-PD1-antibodies and MAPKi, explaining the findings by an enhanced lymphocytic activity opposing tumor adaptive resistance. Recently PD1 was found expressed by a subpopulation of melanoma cells where it could mediate tumorigenic effects, but no data exist showing how MAPKi could modulate its expression. We hypothesized that MAPKi may upregulate PD1 expression and enhance the direct, immune-cell independent antitumor action of anti-PD1 antibodies. We first explore the exact prevalence and magnitude of PD1 expression in patients and cell lines. Then we test the effect of MAPKi on its expression and explore possible immune-independent synergisms with anti-PD1-antibodies. Methodology and results. Prevalence of PD1 expression by melanoma cells was explored in the Cancer Cell Line Encyclopedia (CCLE) and The Cancer Genome Atlas (TCGA) datasets. CCLE included 61 melanoma cell lines, which all expressed PD1 (Affymetrix mRNA 4.20 [3.81- 4.65]) with values comparable to PDL1 (4.63, range 3.73 -7.84) and PDL2 (3.73, range 3.97-8.50). The TCGA analysis included 114 melanomas, excluding those with evidence of immune infiltrate (n=256) or stromal cells (n=100) potentially interfering with PD1 assessment. PD1 mRNA was expressed by all samples (median FPKM values: 64.7, range 0.4-1461.3). Next we assessed by flow-cytometry the membrane expression of PD1 in 4 melanoma cell lines and 3 patient-derived melanoma cultures, harboring BRAF and NRAS mutations We confirmed that low rates of PD1 were expressed by all melanoma (median 1.2%, range 0.7- 4.3). The median rate of viable PD1+ melanoma cells significantly increased (12.9% range 5.9-20, p=0.0180, n =7) following treatment (96h) with MAPKi (dabrafenib and trametinib) but not with chemotherapy (fotemustine). Longer treatments (8 days) further increased the rate of PD1+ melanoma cells (31.8% range 15.0-50.3, n=3) and the effect was reversed by drug withdrawal. The MAPKi modulatory effect on PD1 expression was therapeutically exploited in vitro. The addition of PD1 blocking antibody enhanced the inhibitory activity of MAPKi on melanoma proliferation (mean inhibition rate: 66% vs 40%, n=2) in the absence of any immune cells. Conclusions We report a new expression pattern of PD1 receptor on melanoma and its potential therapeutic perspective. PD1 is directly expressed by a small but consistent rate of melanoma cells. Treatment with MAPKi significantly enhanced the rate of PD1+ melanoma cells and direct synergism with PD1 blockade was reported without the involvement of immune response. Our findings may be clinical relevant in settings of patients treated with MAPKi. Citation Format: Martina Sanlorenzo, Igor Vujic, Arianna Floris, Mauro Novelli, Chiara Donini, Loretta Gammaitoni, Lidia Giraudo, Marco Macagno, Pietro Quaglino, Maria Teresa Fierro, Silvia Giordano, Fabrizio Carnevale-Schianca, Massimo Aglietta, Dario Sangiolo. Melanoma PD1 expression is upregulated by MAPK inhibitors leading to an immune-independent synergism with anti-PD1 antibodies [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 5603. doi:10.1158/1538-7445.AM2017-5603

Highlights of This Issue

Tumor adaptive resistance to therapeutic radiation remains a barrier for further improvement of local cancer control. SIRT3, a member of the sirtuin family of protein deacetylases, prevents cell aging by promoting mitochondrial metabolic homeostasis. Liu and colleagues discovered that SIRT3 was transcriptionally regulated by NF-κB upon radiation, and its enzymatic activity was further enhanced via phosphorylation by mitochondria-localized Cyclin B1–CDK1 complex. Phosphorylation of SIRT3 by CDK1 was required for mitochondrial functions as well as cell survival upon therapeutic radiation shown by in vitro and in vivo radiation tests. Thus, targeting CDK1-mediated SIRT3 phosphorylation is a potential effective approach to enhance tumor response to radiotherapy.Cholangiocarcinoma is a highly malignant carcinoma with poor prognosis. The molecular chaperone, heat shock protein 90 (HSP90), plays an important role in the posttranslational maturation and activation of many critical oncogenic proteins. Here, Shirota and colleagues discovered that the expression of HSP90 was significantly associated with 5-year survival for intrahepatic and extrahepatic cholangiocarcinoma. Furthermore, HSP90 inhibitor NVP-AUY922 showed potent anti- cholangiocarcinoma effect in vitro and in vivo. These data indicate that HSP90 expression is an independent prognostic factor, and that NVP-AUY922 may be an effective treatment option for a subset of patients with cholangiocarcinoma.There is compelling clinical rationale to identify molecular targeting agents that enhance tumor response to radiation. Agents that target MDM2 and p53 are excellent candidates to modulate radiosensitivity. Werner, Huang, and colleauges demonstrate that AMG 232, a potent small molecule MDM2 inhibitor, augments radiation response across a spectrum of human tumors using in vitro and in vivo model systems. Combined AMG 232 and radiation treatment resulted in inhibition of DNA damage repair and induction of senescence, apoptosis, and autophagy. This work previews a promising combination treatment approach for tumors harboring functional p53.Increasing evidence implicates EGFR and HER3 in the modulation of tumor cell response to radiation. In this study, Li, Huang, and colleagues investigate the effect of a dual-specific antibody (MEHD7945A) that simultaneously targets EGFR and HER3 to radiation response in head and neck and lung cancers. The authors found that MEHD7945A enhanced radiation response in both in vitro and in vivo model systems, possibly through an increase of γ-H2AX associated with DNA double-strand breaks and a significant reduction of markers related to tumor proliferation and vasculature. These data suggest the potential value of MEHD7945A as a radiation sensitizer in future clinical trial designs.

Abstract 4978: Lung cancers regulate the immune suppressor PD-L1 by multiple mechanisms, altering its role in tumor survival.

Abstract The immune system has multiple mechanisms by which it can eliminate cancer and yet, tumors are able to adapt resistance to host immune surveillance and continue to survive and grow. One critical resistance mechanism involves Programmed cell death 1 ligand 1 (PD-L1, CD274, B7-H1), the predominant ligand for PD-1, an inhibitory receptor expressed on T cells following activation. PD-L1 also binds to B7.1 (CD80), inhibiting its ability to provide an immune stimulatory signal. PD-L1 is expressed broadly on multiple peripheral blood mononuclear cell subtypes, placenta, and numerous cancers, including NSCLC. Tumor-specific T cells infiltrate tumors and recognize tumor cells, releasing Interferon-gamma (IFNγ), initiating signaling of the Janus kinase/Signal Transducer and Activator of Transcription (JAK/STAT) pathway in the tumor cells. IFNγ induces and/or greatly enhances the expression of PD-L1 in the tumor, among other cell types, allowing the tumor to become resistant to the host T cell response. Blockade of PD-L1 binding to PD-1 and B7.1 can reinvigorate the host immune response against the tumor and overcome tumor adaptive resistance. The regulation of PD-L1 expression is complex and likely involves multiple types of pre- and post-translational events. We show that basal PD-L1 expression levels can vary greatly in cancer cells, as can PD-L1 induction by IFNγ. Here we describe the different categories of PD-L1 basal expression and IFNγ–dependent regulation across multiple lung cell lines and human tumor samples. Reverse Phase Protein Array and RNA microarray data show that the JAK/STAT canonical pathways are still intact among all of these distinct categories, so alternative mechanisms of expression regulation must be active in these cell lines and tumor samples. We provide evidence that a combination of mechanisms regulate both the basal and stimulated expression levels of PD-L1 across these distinct categories. This data regarding PD-L1 expression regulation provides valuable information to better understand the PD-1/PD-L1 pathway as a therapeutic target. Citation Format: Edward (Ward) E. Kadel, Kimberly Walter, Rupal Desai, Juliet Carbon, Marigold Boe, David Shames, Marcin Kowanetz. Lung cancers regulate the immune suppressor PD-L1 by multiple mechanisms, altering its role in tumor survival. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4978. doi:10.1158/1538-7445.AM2013-4978