The proteome of the human breast cancer cell line MDA-MB-231: Analysis by LTQ-Orbitrap mass spectrometry

Small Extracellular Vesicles from Hypoxic Triple-Negative Breast Cancer Cells Induce Oxygen-Dependent Cell Invasion

Hypoxia, a condition of low oxygenation frequently found in triple-negative breast tumors (TNBC), promotes extracellular vesicle (EV) secretion and favors cell invasion, a complex process in which cell morphology is altered, dynamic focal adhesion spots are created, and ECM is remodeled. Here, we investigated the invasive properties triggered by TNBC-derived hypoxic small EV (SEVh) in vitro in cells cultured under hypoxic (1% O₂) and normoxic (20% O₂) conditions, using phenotypical and proteomic approaches. SEVh characterization demonstrated increased protein abundance and diversity over normoxic SEV (SEVn), with enrichment in pro-invasive pathways. In normoxic cells, SEVh promotes invasive behavior through pro-migratory morphology, invadopodia development, ECM degradation, and matrix metalloprotease (MMP) secretion. The proteome profiling of 20% O₂-cultured cells exposed to SEVh determined enrichment in metabolic processes and cell cycles, modulating cell health to escape apoptotic pathways. In hypoxia, SEVh was responsible for proteolytic and catabolic pathway inducement, interfering with integrin availability and gelatinase expression. Overall, our results demonstrate the importance of hypoxic signaling via SEV in tumors for the early establishment of metastasis.

Tumor tissue protein signatures reflect histological grade of breast cancer

Histological grade is one of the most commonly used prognostic factors for patients diagnosed with breast cancer. However, conventional grading has proven technically challenging, and up to 60% of the tumors are classified as histological grade 2, which represents a heterogeneous cohort less informative for clinical decision making. In an attempt to study and extend the molecular puzzle of histologically graded breast cancer, we have in this pilot project searched for additional protein biomarkers in a new space of the proteome. To this end, we have for the first time performed protein expression profiling of breast cancer tumor tissue, using recombinant antibody microarrays, targeting mainly immunoregulatory proteins. Thus, we have explored the immune system as a disease-specific sensor (clinical immunoproteomics). Uniquely, the results showed that several biologically relevant proteins reflecting histological grade could be delineated. In more detail, the tentative biomarker panels could be used to i) build a candidate model classifying grade 1 vs. grade 3 tumors, ii) demonstrate the molecular heterogeneity among grade 2 tumors, and iii) potentially re-classify several of the grade 2 tumors to more like grade 1 or grade 3 tumors. This could, in the long-term run, lead to improved prognosis, by which the patients could benefit from improved tailored care.

99mTc-Glu-c(RGDyK)-Bombesin SPECT Can Reduce Unnecessary Biopsy of Masses That Are BI-RADS Category 4 on Ultrasonography

Masses that, on ultrasonography, are category 4 according to the Breast Imaging Reporting and Data System (BI-RADS) represent possible malignancy, and a biopsy is recommended. This study explored the value of (99m)Tc-Glu-c(RGDyK)-bombesin ((99m)Tc-RGD-bombesin) in reducing unnecessary biopsy of these masses.

METHODS

Ninety women with a BI-RADS 4 mass on ultrasonography were enrolled in this study to undergo breast SPECT using (99m)Tc-RGD-bombesin. The images were independently interpreted using qualitative visual and semiquantitative analyses. The final diagnosis was based on histopathologic examination of surgically excised or percutaneous biopsy specimens. Fractions of the samples were immunohistochemically analyzed to evaluate expression of integrin αvβ3 and gastrin-releasing peptide receptor (GRPR). The receptor-positive group was further divided into 3 subgroups (GRPR(+)/αvβ3 (+), GRPR(+)/αvβ3 (-), and αvβ3 (+)/GRPR(-)).

RESULTS

Ninety-four masses (22 malignant and 72 benign) were confirmed by histopathologic examination. On qualitative analysis, 20 of the malignant masses showed high (99m)Tc-RGD-bombesin accumulation and 48 of the benign masses showed no (99m)Tc-RGD-bombesin accumulation. The optimal cutoff for qualitative analysis was a score of 2. Semiquantitative analysis revealed that 20 of the malignant masses and 16 of the benign masses had a relatively high tumor-to-normal-tissue ratio (T/N). The optimal cutoff was a T/N of 2.26. The mean T/N was higher for malignant masses than for benign masses (3.17 ± 0.86 vs. 1.89 ± 0.71, P < 0.05). T/Ns did not differ among the 3 subgroups (P > 0.05). The areas under the receiver-operating-characteristic curves for the qualitative and semiquantitative analyses were 0.788 and 0.865, respectively, and the overall diagnostic performance did not significantly differ between these analyses (P > 0.05).

CONCLUSION

(99m)Tc-RGD-bombesin SPECT can differentiate benign from malignant BI-RADS 4 masses with high specificity. Further study of the application of this test to clinical breast cancer appears warranted.

An exploratory study on 99mTc-RGD-BBN peptide scintimammography in the assessment of breast malignant lesions compared to 99mTc-3P4-RGD2

PURPOSE

This study aimed to explore the diagnostic performance of single photon emission computed tomography / computerized tomography (SPECT/CT) using a new radiotracer 99mTc-RGD-BBN for breast malignant tumor compared with 99mTc-3P4-RGD2.

METHODS

6 female patients with breast malignant tumors diagnosed by fine needle aspiration cytology biopsy (FNAB) who were scheduled to undergo surgery were included in the study. 99mTc-3P4-RGD2 and 99mTc-RGD-BBN were performed with single photon emission computed tomography (SPECT) at 1 hour after intravenous injection of 299 ± 30 MBq and 293 ± 32 MBq of radiotracers respectively at separate day. The results were evaluated by the Tumor to non-Tumor ratios (T/NT). 99mTc-RGD-BBN and 99mTc-3P4-RGD2 SPECT/CT images were interpreted independently by 3 experienced nuclear medicine physicians using a 3-point scale system. All of the samples were analyzed immunohistochemically to evaluate the integrin αvβ3 and gastrin-releasing peptide receptor (GRPR) expression. The safety, biodistribution and radiation dosimetry of 99mTc-RGD-BBN were also evaluated in the healthy volunteers.

RESULTS

No serious adverse events were reported in any of the patients during the study. The effective radiation dose entirely conformed to the relevant standards. A total of 6 palpable malignant lesions were detected using 99mTc-RGD-BBN SPECT/CT with clear uptake. All malignant lesions were also detected using 99mTc-3P4-RGD2 SPECT/CT. The results showed that five malignant lesions were with clear uptake and the other one with barely an uptake. 4 malignant cases were found with both αvβ3 and GRPR expression, 1 case with only GRPR positive expression (integrin αvβ3 negative) and 1 case with only integrin αvβ3 positive expression (GRPR negative).

CONCLUSION

99mTc-RGD-BBN is a safe agent for detecting breast cancer. 99mTc-RGD-BBN may have the potential to make up for the deficiency of 99mTc-3P4-RGD2 in the detection of breast cancer with only GRPR positive expression (integrin αvβ3 negative). The preliminary application of 99mTc-RGD-BBN has demonstrated its powerful potential in breast cancer diagnosis and therapy.

Grading breast cancer tissues using molecular portraits

Tumor progression and prognosis in breast cancer patients are difficult to assess using current clinical and laboratory parameters, where a pathological grading is indicative of tumor aggressiveness. This grading is based on assessments of nuclear grade, tubule formation, and mitotic rate. We report here the first protein signatures associated with histological grades of breast cancer, determined using a novel affinity proteomics approach. We profiled 52 breast cancer tissue samples by combining nine antibodies and label-free LC-MS/MS, which generated detailed quantified proteomic maps representing 1,388 proteins. The results showed that we could define in-depth molecular portraits of histologically graded breast cancer tumors. Consequently, a 49-plex candidate tissue protein signature was defined that discriminated between histological grades 1, 2, and 3 of breast cancer tumors with high accuracy. Highly biologically relevant proteins were identified, and the differentially expressed proteins indicated further support for the current hypothesis regarding remodeling of the tumor microenvironment during tumor progression. The protein signature was corroborated using meta-analysis of transcriptional profiling data from an independent patient cohort. In addition, the potential for using the markers to estimate the likelihood of long-term metastasis-free survival was also indicated. Taken together, these molecular portraits could pave the way for improved classification and prognostication of breast cancer.

Deeper in the human cornea proteome using nanoLC-Orbitrap MS/MS: An improvement for future studies on cornea homeostasis and pathophysiology

The cornea is a transparent, avascular, and highly specialized connective tissue that provides the majority of light refraction in the optical system of the eye. The human cornea is composed of several layers interacting in a complex manner and possessing specific functions, like eye protection and optical clearness. Only few proteomic studies of mammalian cornea have been performed leading to the identification of less than 200 proteins in human corneas. The present study explores the proteome of the intact normal human cornea using a shot-gun nanoLC-MS/MS strategy and an LTQ Orbitrap mass spectrometer. A total of 2070 distinct corneal proteins were identified from five human cornea samples, which represents a 14-fold improvement in the number of proteins identified so far for human cornea. This enlarged dataset of human corneal proteins represents a valuable reference library for further studies on cornea homeostasis and pathophysiology. Network and gene ontology analyses were used to determine biological pathways specific of the human cornea. They allowed the identification of subnetworks of putative importance for corneal diseases, like a redox regulation and oxidative stress network constituted of aldehyde and alcohol dehydrogenases, most of them being described for the first time in human cornea.

(18)F, (64)Cu, and (68)Ga labeled RGD-bombesin heterodimeric peptides for PET imaging of breast cancer

Radiolabeled RGD (Arg-Gly-Asp) and bombesin (BBN) radiotracers that specifically target integrin alpha(v)beta(3) and gastrin releasing peptide receptor (GRPR) are both promising radiopharmaceuticals for tumor imaging. We recently designed and synthesized a RGD-BBN heterodimeric peptide with both RGD and BBN motifs in one single molecule. The (18)F-labeled RGD-BBN heterodimer exhibited dual integrin alpha(v)beta(3) and GRPR targeting in a PC-3 prostate cancer model. In this study we investigated whether radiolabeled RGD-BBN tracers can be used to detect breast cancer by using microPET. Cell binding assay demonstrated that the high GRPR expressing breast cancer cells typically express low to moderate level of integrin alpha(v)beta(3), while high integrin alpha(v)beta(3) expressing breast cancer cells have negligible level of GRPR. We labeled RGD-BBN heterodimer with three positron emitting radionuclides (18)F, (64)Cu, and (68)Ga and investigated the corresponding PET radiotracers in both orthotopic T47D (GRPR(+)/low integrin alpha(v)beta(3)) and MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) breast cancer models. The three radiotracers all possessed in vitro dual integrin alpha(v)beta(3) and GRPR binding affinity. The advantages of the RGD-BBN radiotracers over the corresponding BBN analogues are obvious for imaging MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) tumor. (18)F-FB-PEG(3)-RGD-BBN showed lower tumor uptake than (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN but was able to visualize breast cancer tumors with high contrast. Synthesis of (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN is much faster and easier than (18)F-FB-PEG(3)-RGD-BBN. (64)Cu-NOTA-RGD-BBN showed prolonged tumor uptake but also higher liver retention and kidney uptake than (68)Ga-NOTA-RGD-BBN and (18)F-FB-PEG(3)-RGD-BBN. (68)Ga-NOTA-RGD-BBN possessed high tumor signals but also relatively high background uptake compared with the other two radiotracers. In summary, the prosthetic labeling groups, chelators, and isotopes all have a profound effect on the tumor targeting efficacy and in vivo kinetics of the RGD-BBN tracers for dual integrin and GRPR recognition. Further development of suitably labeled RGD-BBN tracers for PET imaging of cancer is warranted.