Real-time monitoring of tumorigenesis, dissemination, & drug response in a preclinical model of lymphangioleiomyomatosis/tuberous sclerosis complex

Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is an ultra-rare, slowly progressive neoplastic cystic disease, belonging to the group of PEComas. It can occur sporadically or associated to tuberous sclerosis complex disease and affects mainly women in child-birth age. Dyspnoea is the most frequent symptom referred to the time of diagnosis, however spontaneous pneumothorax may be a typical presentation associated to extrathoracic manifestations, such as renal angiomyolipomas. In the last decade, important advances in understanding molecular mechanisms underlying the LAM pathogenesis have been reached. It has allowed to obtain improvements in the research of novel biomarkers, treatment and a better management of the disease.

Near-Infrared Contrast Agents for Bone-Targeted Imaging

Background

For the bone-specific imaging, a structure-inherent targeting of bone tissue recently has been reported a new strategy based on incorporation of targeting moieties into the chemical structure of near-infrared (NIR) contrast agents, while conventional methods require covalent conjugation of bone-targeting ligands to NIR contrast agents. This will be a new approach for bone-targeted imaging by using the bifunctional NIR contrast agents.

Methods

The goal of this review is to provide an overview of the recent advances in optical imaging of bone tissue, highlighting the structure-inherent targeting by developing NIR contrast agents without the need for a bone-targeting ligand such as bisphosphonates.

Results

A series of iminodiacetated and phosphonated NIR contrast agents for the structure-inherent targeting of bone tissue showed excellent bone-targeting ability in vivo without non-specific binding. Additionally, the phosphonated NIR contrast agents could be useful in the diagnosis of bone metastasis.

Conclusion

By developing bone-targeted NIR contrast agents, optical imaging of bone tissue makes it very attractive for preclinical studies of bone growth or real-time fluorescence guided surgery resulting in high potential to shift the clinical paradigms.

Proapoptotic protein Bim attenuates estrogen-enhanced survival in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a progressive lung disease that primarily affects young women. Genetic evidence suggests that LAM cells bearing TSC2 mutations migrate to the lungs, proliferate, and cause cystic remodeling. The female predominance indicates that estrogen plays a critical role in LAM pathogenesis, and we have proposed that estrogen promotes LAM cell metastasis by inhibition of anoikis. We report here that estrogen increased LAM patient-derived cells' resistance to anoikis in vitro, accompanied by decreased accumulation of the proapoptotic protein Bim, an activator of anoikis. The resistance to anoikis was reversed by the proteasome inhibitor, bortezomib. Treatment of LAM patient-derived cells with estrogen plus bortezomib promoted anoikis compared with estrogen alone. Depletion of Bim by siRNA in TSC2-deficient cells resulted in anoikis resistance. Treatment of mice with bortezomib reduced estrogen-promoted lung colonization of TSC2-deficient cells. Importantly, molecular depletion of Bim by siRNA in Tsc2-deficient cells increased lung colonization in a mouse model. Collectively, these data indicate that Bim plays a key role in estrogen-enhanced survival of LAM patient-derived cells under detached conditions that occur with dissemination. Thus, targeting Bim may be a plausible future treatment strategy in patients with LAM.

Charge and hydrophobicity effects of NIR fluorophores on bone-specific imaging

Recent advances in near-infrared (NIR) fluorescence imaging enabled real-time intraoperative detection of bone metastases, bone growth, and tissue microcalcification. Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects. Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance. Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

Microscopic validation of macroscopic in vivo images enabled by same-slide optical and nuclear fusion

It is currently difficult to determine the molecular and cellular basis for radioscintigraphic signals obtained during macroscopic in vivo imaging. The field is in need of technology that helps bridge the macroscopic and microscopic regimes. To solve this problem, we developed a fiducial marker (FM) simultaneously compatible with 2-color near-infrared (NIR) fluorescence (700 and 800 nm), autoradiography, and conventional hematoxylin-eosin (HE) histology.

METHODS

The FM was constructed from an optimized concentration of commercially available human serum albumin, 700- and 800-nm NIR fluorophores, (99m)Tc-pertechnetate, dimethyl sulfoxide, and glutaraldehyde. Lymphangioleiomyomatosis cells coexpressing the sodium iodide symporter and green fluorescent protein were labeled with 700-nm fluorophore and (99m)Tc-pertechnatate and then administered intratracheally into CD-1 mice. After in vivo SPECT imaging and ex vivo SPECT and NIR fluorescence imaging of the lungs, 30-μm frozen sections were prepared and processed for 800-nm NIR fluorophore costaining, autoradiography, and HE staining on the same slide using the FMs to coregister all datasets.

RESULTS

Optimized FMs, composed of 100 μM unlabeled human serum albumin, 1 μM NIR fluorescent human serum albumin, 15% dimethyl sulfoxide, and 3% glutaraldehyde in phosphate-buffered saline (pH 7.4), were prepared within 15 min, displayed homogeneity and stability, and were visible by all imaging modalities, including HE staining. Using these FMs, tissue displaying high signal by SPECT could be dissected and analyzed on the same slide and at the microscopic level for 700-nm NIR fluorescence, 800-nm NIR fluorescence, autoradiography, and HE histopathologic staining.

CONCLUSION

When multimodal FMs are combined with a new technique for simultaneous same-slide NIR fluorescence imaging, autoradiography, and HE staining, macroscopic in vivo images can now be studied unambiguously at the microscopic level.

Progesterone and estradiol synergistically promote the lung metastasis of tuberin-deficient cells in a preclinical model of lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a female-predominant lung disease that can lead to respiratory failure. LAM cells typically have inactivating tuberous sclerosis 2 (TSC2) mutations, leading to mTORC1 hyperactivation. The gender specificity of LAM suggests that female hormones contribute to disease progression. Clinical findings indicate that estradiol exacerbates LAM behaviors and symptoms. Although hormonal therapy with progesterone has been employed, the benefit in LAM improvement has not been achieved. We have previously found that estradiol promotes the survival and lung metastasis of cells lacking tuberin in a preclinical model of LAM. In this study, we hypothesize that progesterone alone or in combination with estradiol promotes metastatic behaviors of TSC2-deficient cells. In cell culture models of TSC2-deficient LAM patient-derived and rat uterine leiomyoma-derived cells, we found that progesterone treatment or progesterone plus estradiol resulted in increased phosphorylation of Protein Kinase B (Akt) and Extracellular signal-regulated kinases1/2 (ERK1/2), induced the proliferation, and enhanced the migration and invasiveness. In addition, treatment of progesterone plus estradiol synergistically decreased the levels of reactive oxygen species and enhanced cell survival under oxidative stress. In a murine model of LAM, treatment of progesterone plus estradiol promoted the growth of xenograft tumors; however, progesterone treatment did not affect the development of xenograft tumors of Tsc2-deficient cells. Importantly, treatment of progesterone plus estradiol resulted in alteration of lung morphology and significantly increased the number of lung micrometastases of Tsc2-deficient cells compared with estradiol treatment alone. Collectively, these data indicate that progesterone increases the metastatic potential of Tsc2-deficient LAM patient-derived cells in vitro and lung metastasis in vivo. Thus, targeting progesterone-mediated signaling events may have therapeutic benefit for LAM and possibly other hormonally dependent cancers.

Estradiol and mTORC2 cooperate to enhance prostaglandin biosynthesis and tumorigenesis in TSC2-deficient LAM cells

Lymphangioleiomyomatosis (LAM) is a progressive neoplastic disorder that leads to lung destruction and respiratory failure primarily in women. LAM is typically caused by tuberous sclerosis complex 2 (TSC2) mutations resulting in mTORC1 activation in proliferative smooth muscle-like cells in the lung. The female predominance of LAM suggests that estradiol contributes to disease development. Metabolomic profiling identified an estradiol-enhanced prostaglandin biosynthesis signature in Tsc2-deficient (TSC(-)) cells, both in vitro and in vivo. Estradiol increased the expression of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostaglandin biosynthesis, which was also increased at baseline in TSC-deficient cells and was not affected by rapamycin treatment. However, both Torin 1 treatment and Rictor knockdown led to reduced COX-2 expression and phospho-Akt-S473. Prostaglandin production was also increased in TSC-deficient cells. In preclinical models, both Celecoxib and aspirin reduced tumor development. LAM patients had significantly higher serum prostaglandin levels than healthy women. 15-epi-lipoxin-A4 was identified in exhaled breath condensate from LAM subjects and was increased by aspirin treatment, indicative of functional COX-2 expression in the LAM airway. In vitro, 15-epi-lipoxin-A4 reduced the proliferation of LAM patient-derived cells in a dose-dependent manner. Targeting COX-2 and prostaglandin pathways may have therapeutic value in LAM and TSC-related diseases, and possibly in other conditions associated with mTOR hyperactivation.

Sex-specific lung diseases: effect of oestrogen on cultured cells and in animal models

Sex prevalence in lung disease suggests that sex-specific hormones may contribute to the pathogenesis and/or progression of at least some lung diseases, such as lung adenocarcinoma, lymphangioleiomyomatosis (LAM) and benign metastasising leiomyoma (BML). Oestrogen is an important hormone in normal lung development and in the pathogenesis of female predominant pulmonary diseases. In vivo and in vitro studies have facilitated our understanding of disease pathogenesis and discovery of potential therapeutic targets. Oestrogen promoted disease progression in cell and animal models of lung adenocarcinoma, LAM and BML. Specifically, oestrogen enhanced tumour growth and metastasis in animal models of these diseases. Furthermore, 17β-estradiol (E2), the most abundant form of oestrogen in humans, increased the size and proliferation of cultured cells of lung adenocarcinoma and LAM. Coupled with the known mechanisms of oestrogen metabolism and signalling, these model systems may provide insights into the diverse effects of oestrogen and other hormones on lung diseases. Anti-oestrogen treatments that target key events of oestrogen synthesis or signalling, such as aromatase activity, oestrogen receptors and signalling pathways, may offer additional opportunities for clinical trials.

Imaging mouse cancer models in vivo using reporter transgenes

Imaging mouse models of cancer with reporter transgenes has become a relatively common experimental approach in the laboratory, which allows noninvasive and longitudinal investigation of diverse aspects of tumor biology in vivo. Our goal here is to outline briefly the principles of the relevant imaging modalities, emphasizing particularly their strengths and weaknesses and what the researcher can expect in a practical sense from each of these techniques. Furthermore, we discuss how relatively subtle modifications in the way reporter transgene expression is regulated in the cell underpin the ability of reporter transgenes as a whole to provide readouts on such varied aspects of tumor biology in vivo.

Uterine-specific loss of Tsc2 leads to myometrial tumors in both the uterus and lungs

Lymphangioleiomyomatosis (LAM) is a rare disease characterized by proliferation of abnormal smooth-muscle cells in the lungs, leading to functional loss and sometimes lung transplantation. Although the origin of LAM cells is unknown, several features of LAM provide clues. First, LAM cells contain inactivating mutations in genes encoding Tsc1 or Tsc2, proteins that limit mTORC1 activity. Second, LAM tumors recur after lung transplantation, suggesting a metastatic pathogenesis. Third, LAM is found almost exclusively in women. Finally, LAM shares features with uterine leiomyomas, benign tumors of myometrial cells. From these observations, we proposed that LAM cells might originate from uterine leiomyomas containing Tsc mutations. To test our hypothesis, and to develop mouse models for leiomyoma and LAM, we targeted Tsc2 deletion primarily in uterine cells. In fact, nearly 100% of uteri from uterine-specific Tsc2 knockout mice developed myometrial proliferation and uterine leiomyomas by 12 and 24 weeks, respectively. Myometrial proliferation and mTORC1/S6 activity were abrogated by the mTORC1 inhibitor rapamycin or by elimination of sex steroid production through ovariectomy or aromatase inhibition. In ovariectomized Tsc2 null mice, mTORC1/S6 activity and myometrial growth were restored by estrogen but not progesterone. Thus, even without Tsc2, estrogen appears to be required for myometrial mTORC1/S6 signaling and proliferation. Finally, we found Tsc2 null myometrial tumors in lungs of older Tsc2 uterine-specific knockout females, suggesting that lung LAM-like myometrial lesions may indeed originate from the uterus. This mouse model may improve our understanding of LAM and leiomyomas and might lead to novel therapeutic strategies for both diseases.

Lymphangioleiomyomatosis: current and future

Lymphangioleiomyomatosis is a rare slowly progressive lung disease that affects almost exclusively young women of reproductive age. It occurs sporadically or in association with Tuberous Sclerosis Complex. LAM is characterized by cystic remodeling of the lung parenchyma, due to proliferation of abnormal smooth muscle-like LAM cells and presence of extra pulmonary manifestations such as lymphadenopathy, angiomyolipomas and abdominal lymphangioleiomyomas. The most common clinical manifestations are progressive dyspnea on exertion, pneumothorax and chylous effusions. Currently there is no curative treatment for the disease, but the ongoing study of the genetic and molecular pathways implicated in the pathogenesis of the disease could lead to targeted therapy.