Pharmacological induction of membrane lipid poly-unsaturation sensitizes melanoma to ROS inducers and overcomes acquired resistance to targeted therapy

BACKGROUND

One of the key limitations of targeted cancer therapies is the rapid onset of therapy resistance. Taking BRAF-mutant melanoma as paradigm, we previously identified the lipogenic regulator SREBP-1 as a central mediator of resistance to MAPK-targeted therapy. Reasoning that lipogenesis-mediated alterations in membrane lipid poly-unsaturation lie at the basis of therapy resistance, we targeted fatty acid synthase (FASN) as key player in this pathway to evoke an exquisite vulnerability to clinical inducers of reactive oxygen species (ROS), thereby rationalizing a novel clinically actionable combination therapy to overcome therapy resistance.

METHODS

Using gene expression analysis and mass spectrometry-based lipidomics of BRAF-mutant melanoma cell lines, melanoma PDX and clinical data sets, we explored the association of FASN expression with membrane lipid poly-unsaturation and therapy-resistance. Next, we treated therapy-resistant models with a preclinical FASN inhibitor TVB-3664 and a panel of ROS inducers and performed ROS analysis, lipid peroxidation tests and real-time cell proliferation assays. Finally, we explored the combination of MAPK inhibitors, TVB-3664 and arsenic trioxide (ATO, as a clinically used ROS-inducer) in Mel006 BRAF mutant PDX as a gold model of therapy resistance and assessed the effect on tumor growth, survival and systemic toxicity.

RESULTS

We found that FASN expression is consistently increased upon the onset of therapy resistance in clinical melanoma samples, in cell lines and in Mel006 PDX and is associated with decreased lipid poly-unsaturation. Forcing lipid poly-unsaturation in therapy-resistant models by combining MAPK inhibition with FASN inhibition attenuated cell proliferation and rendered cells exquisitely sensitive to a host of ROS inducers. In particular, the triple combination of MAPK inhibition, FASN inhibition, and the clinical ROS-inducing compound ATO dramatically increased survival of Mel006 PDX models from 15 to 72% with no associated signs of toxicity.

CONCLUSIONS

We conclude that under MAPK inhibition the direct pharmacological inhibition of FASN evokes an exquisite vulnerability to inducers of ROS by increasing membrane lipid poly-unsaturation. The exploitation of this vulnerability by combining MAPK and/or FASN inhibitors with inducers of ROS greatly delays the onset of therapy resistance and increases survival. Our work identifies a clinically actionable combinatorial treatment for therapy-resistant cancer.

A palmitate-rich metastatic niche enables metastasis growth via p65 acetylation resulting in pro-metastatic NF-κB signaling

Metabolic rewiring is often considered an adaptive pressure limiting metastasis formation; however, some nutrients available at distant organs may inherently promote metastatic growth. We find that the lung and liver are lipid-rich environments. Moreover, we observe that pre-metastatic niche formation increases palmitate availability only in the lung, whereas a high-fat diet increases it in both organs. In line with this, targeting palmitate processing inhibits breast cancer-derived lung metastasis formation. Mechanistically, breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a-dependent manner. Concomitantly, lysine acetyltransferase 2a expression is promoted by palmitate, linking the available acetyl-CoA to the acetylation of the nuclear factor-kappaB subunit p65. Deletion of lysine acetyltransferase 2a or carnitine palmitoyltransferase 1a reduces metastasis formation in lean and high-fat diet mice, and lung and liver metastases from patients with breast cancer show coexpression of both proteins. In conclusion, palmitate-rich environments foster metastases growth by increasing p65 acetylation, resulting in a pro-metastatic nuclear factor-kappaB signaling.

Abstract C077: Evidence for a tumoral temperature driven chemoresistance pathway in pancreatic cancer

Tumor growth is inevitably accompanied by changes in the tumor-microenvironment to which cancer cells have to adapt in order to thrive. Alterations in metabolism and blood perfusion of solid tumors have been suggested to drive a spontaneous increase in tumoral temperature. However, it is currently unknown if this phenomenon affects cancer biology. We found increased temperature in human pancreatic ductal adenocarcinoma (PDAC) tumors. By mimicking this observation in PDAC cell lines, we found that cancer cells adapt to tumoral temperature by altering the cellular lipidome and accordingly evade ferroptosis, a lipid-dependent form of cell death. We found evidence that tumoral temperature-induced ferroptosis evasion depends on p38-MAPK deactivation and ultimately drives resistance to the chemotherapeutic drug gemcitabine. Collectively, our findings suggest a direct role for p38-dependend ferroptosis evasion in gemcitabine resistance, and we identify tumoral temperature as a pathophysiological driver of this process. Our discovery unveils temperature as an unexplored hallmark of the tumor-microenvironment.

Citation Format: Vincent de Laat, Halit Topal, Jonas Dehairs, Xander Spotbeen, Ali Talebi, Frank Vanderhoydonc, Tessa Ostyn, Tania Roskams, Baki Topal, Johan Swinnen. Evidence for a tumoral temperature driven chemoresistance pathway in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C077.

Lipidomic profiling of clinical prostate cancer reveals targetable alterations in membrane lipid composition

Dysregulated lipid metabolism is a prominent feature of prostate cancer that is driven by androgen receptor (AR) signaling. Here we used quantitative mass spectrometry to define the "lipidome" in prostate tumors with matched benign tissues (n=21), independent unmatched tissues (n=47), and primary prostate explants cultured with the clinical AR antagonist enzalutamide (n=43). Significant differences in lipid composition were detected and spatially visualized in tumors compared to matched benign samples. Notably, tumors featured higher proportions of monounsaturated lipids overall and elongated fatty acid chains in phosphatidylinositol and phosphatidylserine lipids. Significant associations between lipid profile and malignancy were validated in unmatched samples, and phospholipid composition was characteristically altered in patient tissues that responded to AR inhibition. Importantly, targeting tumor-related lipid features via inhibition of acetyl-CoA carboxylase 1 significantly reduced cellular proliferation and induced apoptosis in tissue explants. This first characterization of the prostate cancer lipidome in clinical tissues reveals enhanced fatty acid synthesis, elongation, and desaturation as tumor-defining features, with potential for therapeutic targeting.

Abstract 2076: Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis

Membranes are unique phospholipid (PL) interfaces that play a central role in cancer cell biology. However, PL composition of clinical tumors, and its dynamic regulation, remains a critical gap in the molecular profiling of this disease. Here, we used mass spectrometry-based spatial imaging and lipidomics to generate PL profiles of clinical prostate tissues upon cancer development and in patient-derived tumor explants (PDEs; n=43) cultured with the current clinical agent enzalutamide. Analysis of more than 100 PL species in tumors and matched normal tissues from 21 patients revealed a complexity of cancer-related changes in the tissue PL landscape. Phosphatidylcholine (PC)-based PLs were the most abundant PL class, and their relative abundance was increased in tumors compared to matched benign tissues. A greater proportion of monounsaturated fatty acid chains was characteristic of PLs in tumors, most evident in the PC and phosphatidylethanolamine (PE) PLs, as was striking elongation of fatty acid chains in the phosphatidylinositol (PI) and phosphatidylserine (PS) classes. The abundance of specific PL species and saturation groups was significantly associated with malignancy in both this and an independent cohort of unmatched patient tissues (n=47). Notably, the PL profile was significantly associated with the ERG molecular subtype and basal proliferative index (Ki67) in tumors. Furthermore, we identified individual PL species that were associated with the antiproliferative response to enzalutamide, in cultured PDEs. In light of these PL features, we proposed acetyl coA carboxylase (ACC) as a novel therapeutic target in prostate cancer. Indeed, blocking lipid biosynthesis and elongation in prostate tumors with an ACC inhibitor (ACCi, PF-05175157) significantly reduced tumor cell proliferation in PDE tissues (n=13), concomitant with increased pACC1 staining and a decreased proportion of longer chain PLs. Our findings suggest that the clinical PCa lipidome is not only a marker of malignant transformation and aggressiveness, but also therapeutic response to enzalutamide. Moreover, defining this unique biology identified further clinically actionable targets that may improve prostate cancer outcomes.

Citation Format: Lisa M. Butler, Chui Yan Mah, Jonas Dehairs, Andrew Vincent, Shadrack Mutuku, Xander Spotbeen, Rajdeep Das, Zeyad Nassar, Luke Selth, Paul Trim, Marten Snel, David Lynn, Lisa Horvath, Wayne Tilley, Margaret Centenera, Johannes Swinnen. Phospholipid profiling of clinical prostate tissues reveals targetable alterations in membrane lipid composition accompanying tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2076.