PET imaging of Hsp90 expression in pancreatic cancer using a new 64Cu-labeled dimeric Sansalvamide A decapeptide

Synthesis and characterization of 64Cu-labeled Geldanamycin derivative for imaging HSP90 expression in breast cancer

Heat shock protein 90 (HSP90) plays a crucial role in cancer cell growth and metastasis by stabilizing overexpressed signaling proteins. Inhibiting HSP90 has emerged as a promising anti-cancer strategy. In this study, we aimed to develop and characterize a HSP90-targeted molecular imaging probe, [64Cu]Cu-DOTA-BDA-GM, based on a specific HSP90 inhibitor, geldanamycin (GM), for PET imaging of cancers. GM is modified at the C-17 position with 1,4-butane-diamine (BDA) and linked to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for 64Cu radiolabeling. We evaluated the probe's specific binding to HSP90-expressing cells using Chinese hamster ovary (CHO) cells and breast cancer cells including MDA-MB-231, MDA-MB-435S, MCF7, and KR-BR-3 cell lines. A competition study with non-radioactive GM-BDA yielded an IC50 value of 1.35 ± 0.14 nM, underscoring the probe's affinity for HSP90. In xenograft models of MDA-MB-231 breast cancer, [64Cu]Cu-DOTA-BDA-GM showcased targeted tumor localization, with significant radioactivity observed up to 18 h post-injection. Blocking studies using unlabeled GM-BDA and treatment with the anticancer drug Vorinostat (SAHA), which can affect the expression and activity of numerous proteins, such as HSPs, confirmed the specificity and sensitivity of the probe in cancer targeting. Additionally, PET/CT imaging in a lung metastasis mouse model revealed increased lung uptake of [64Cu]Cu-DOTA-BDA-GM in metastatic sites, significantly higher than in non-metastatic lungs, illustrating the probe's ability to detect metastatic breast cancer. In conclusion, [64Cu]Cu-DOTA-BDA-GM represents a sensitive and specific approach for identifying HSP90 expression in breast cancer and metastases, offering promising implications for clinical diagnosis and monitoring.

Anti-cancer properties of Sansalvamide A, its derivatives, and analogs: an updated review

As peptide-based therapies gain recognition for their potential anti-cancer activity, cyclic peptides like Sansalvamide A, a marine-derived cyclic depsipeptide, have emerged as a potential anti-cancer agent due to their potent activity against various cancer types in preclinical studies. This review offers a comprehensive overview of Sansalvamide A, including its sources, structure-activity relationship, and semi-synthetic derivatives. The review also aims to outline the mechanisms through which Sansalvamide A and its analogs exert their anti-proliferative effects and to discuss the need for enhancements in pharmacokinetic profiles for better clinical utility. An extensive literature search was conducted, focusing on studies that detailed the anti-cancer activity of Sansalvamide A, its pharmacokinetics, and mechanistic pathways. Data from both in vitro and in vivo studies were collated and analyzed. Sansalvamide A and its analogs demonstrated significant anti-cancer activity across various cancer models, mediated through Hsp 90 inhibition, Topoisomerase inhibition, and G0/G1 cell cycle arrest. However, their pharmacokinetic properties were identified as a significant limitation, requiring improvement for effective clinical translation. Despite its notable anti-cancer effects, the utility of Sansalvamide A is currently limited by its pharmacokinetic characteristics. Therefore, while Sansalvamide A exhibits promise as an anti-cancer agent, there is a compelling need for further clinical and toxicological studies and optimization of its pharmacokinetic profile to fully exploit its therapeutic potential alongside modern cancer therapies.

Antimicrobial peptides as potential therapy for gastrointestinal cancers

Since conventional therapy faces limitations in the field of different cancers as well as gastrointestinal cancers, that decrease the survival rate of patients, there is an urgent need to find new effective therapeutic approaches without the adverse effects of the traditional agents. Antimicrobial peptides (AMPs) attract much attention and are well known for their role in innate immunity. These peptides, in addition to their antimicrobial activity, exhibit strong anticancer potential against various types of malignancy. AMPs specifically target tumor cells and have selective toxicity for these cells without affecting normal cells. Here we aim to comprehensively overview the current knowledge in the field of using AMPs as novel therapeutic agents for gastrointestinal cancer.

18F-labeled Dimer-Sansalvamide A Cyclodecapeptide: A Novel Diagnostic Probe to Discriminate Pancreatic Cancer from Inflammation in a Nude Mice Model

Early detection of pancreatic cancer has been a long-standing challenge. Inflammatory mass is the main source of false-positive findings in ¹⁸F-labeled fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography / computed tomography (PET/CT). Heat shock protein 90 (Hsp90) is an established biomarker overexpressed in pancreatic cancer. We modified a Dimer-Sansalvamide A cyclodecapeptide by conjugating it with the bifunctional chelator NOTA (1,4,7-triazacyclononane-1,4,7-trisacetic acid), yielding ¹⁸F-NOTA-Dimer-Sansalvamide A cyclodecapeptide (¹⁸F-NOTA-Dimer-San A). The binding specificity of the probe was confirmed by in vitro cell uptake assays in Hsp90-positive PL45 pancreatic cancer cells. Hsp90 expression was imaged via MicroPET in pancreatic cancer xenografts and inflammation in mice. All of the mice received an intravenous injection of ¹⁸F-NOTA-Dimer-San A, and images were acquired at 1 and 2 hour time points. The novel probe demonstrated prominent tumor uptake in the pancreatic cancer xenografts (4.00 ± 0.88 %ID/g, 5.80 ± 0.94 %ID/g), and the inflammatory thigh showed minimal uptake (0.85 ± 0.01 %ID/g, 1.50 ± 0.20 %ID/g) at 1 and 2 hours after injection, respectively. The activity accumulation between the two groups was significantly different (P < 0.05), and the biodistribution data was consistent with the images. Moreover, immunohistochemistry (IHC) confirmed that the expression of Hsp90 was positive in PL45 pancreatic cancer but negative in the muscles next to the tumor and inflammatory muscles. We concluded that ¹⁸F-NOTA-Dimer-San A PET might allow non-invasive imaging for Hsp90 expression in tumors and has the potential to discriminate pancreatic cancer from inflammatory mass.

Recent Advances in Small Peptides of Marine Origin in Cancer Therapy

Cancer is one of the leading causes of death in the world, and antineoplastic drug research continues to be a major field in medicine development. The marine milieu has thousands of biological species that are a valuable source of novel functional proteins and peptides, which have been used in the treatment of many diseases, including cancer. In contrast with proteins and polypeptides, small peptides (with a molecular weight of less than 1000 Da) have overwhelming advantages, such as preferential and fast absorption, which can decrease the burden on human gastrointestinal function. Besides, these peptides are only connected by a few peptide bonds, and their small molecular weight makes it easy to modify and synthesize them. Specifically, small peptides can deliver nutrients and drugs to cells and tissues in the body. These characteristics make them stand out in relation to targeted drug therapy. Nowadays, the anticancer mechanisms of the small marine peptides are still largely not well understood; however, several marine peptides have been applied in preclinical treatment. This paper highlights the anticancer linear and cyclic small peptides in marine resources and presents a review of peptides and the derivatives and their mechanisms.

Targeted Imaging Agent to HSP70 Induced In Vivo

Heat shock protein expression can be induced by heat shock making it possible to artificially modulate their levels noninvasively in vivo in a spatially and temporally controlled manner. Here, we report the use of the major heat shock protein 70 (HSP70) as an inducible target by using the small molecule deoxyspergualin (DSG) conjugated to the near-infrared fluorophore (Cy5.5). We demonstrate that heat induction in the form of localized hyperthermia of normal tissue in living mice results in sufficient HSP70 overexpression for detection with DSG-Cy5.5 conjugate. This effect is dependent on total energy delivered and reaches maximum fluorescence signal in 6 to 8 hours post heat induction and declines over a period of up to 24 hours. These results suggest that DSG-Cy5.5 agent accumulates in tissue with elevated HSP70 by heat.

Synthesis and Preclinical Evaluation of a 68Ga-Radiolabeled Peptide Targeting Very Late Antigen-3 for PET Imaging of Pancreatic Cancer

Pancreatic cancer is highly malignant and has a five-year survival rate of 5% due to an early lymph node, nerve, and vascular metastasis. Integrin α3β1 (also called very late antigen-3, VLA-3) is overexpressed in many tumors and plays a vital role in tumor formation, recurrence, and metastasis. In this study, we developed a 68Ga-radiolabeled peptide tracer targeting the α3 unit of VLA-3 and evaluated its potential application in positron emission computed tomography (PET) imaging of pancreatic cancer. NOTA-CK11 was prepared by solid-phase synthesis and successfully radiolabeled with 68Ga with greater than 99% radiochemical purity and a specific activity of 37 ± 5 MBq/nmol (n = 5). The expression level of integrin α3 in three human pancreatic cancer cells was evaluated with the order of SW1990, BXPC-3, and PANC-1 from high to low, while the expression level of integrin β1 was relatively close. When SW1990 cells with the highest expression level of VLA-3 were stained with FITC-CK11, strong fluorescence was observed by flow cytometry and under a laser confocal microscope. However, no significant fluorescence was observed in the blocking group when treated with excessive CK11. 68Ga-NOTA-CK11 showed significant radioactivity accumulation in SW1990 cells and was blocked by CK11 successfully. Subsequent small-animal PET imaging and biodistribution studies in mice bearing SW1990 xenografts confirmed its high tumor uptake with a good tumor-to-blood ratio and tumor-to-muscle ratio (2.45 ± 0.31 and 3.65 ± 0.33, respectively) at 1 h post injection of the probe. In summary, we successfully developed a peptide-based imaging agent, 68Ga-NOTA-CK11, that showed a strong binding affinity with VLA-3 and good target specificity for SW1990 cells and xenografted pancreatic tumor, rending it a promising radiotracer for PET imaging of VLA-3 expression in pancreatic cancer.

Evaluation of [11C]NMS-E973 as a PET tracer for in vivo visualisation of HSP90

Heat shock protein 90 is an ATP-dependent molecular chaperone important for folding, maturation and clearance of aberrantly expressed proteins and is abundantly expressed (1-2% of all proteins) in the cytosol of all normal cells. In some tumour cells, however, strong expression of HSP90 is also observed on the cell membrane and in the extracellular matrix and the affinity of tumoural HSP90 for ATP domain inhibitors was reported to increase over 100-fold compared to that of HSP90 in normal cells. Here, we explore [¹¹C]NMS-E973 as a PET tracer for in vivo visualisation of HSP90 and as a potential tool for in vivo quantification of occupancy of HSP90 inhibitors.

Methods: HSP90 expression was biochemically characterized in a panel of established cell lines including the melanoma line B16.F10. B16.F10 melanoma xenograft tumour tissue was compared to non-malignant mouse tissue. NMS-E973 was tested in vitro for HSP90 inhibitory activity in several tumour cell lines. HSP90-specific binding of [¹¹C]NMS-E973 was evaluated in B16.F10 melanoma cells and B16.F10 melanoma, prostate cancer LNCaP and PC3, SKOV-3 xenograft tumour slices and in vivo in a B16.F10 melanoma mouse model.

Results: Strong intracellular upregulation and abundant membrane localisation of HSP90 was observed in the different tumour cell lines, in the B16.F10 tumour cell line and in B16.F10 xenograft tumours compared to non-malignant tissue. NMS-E973 showed HSP90-specific inhibition and reduced proliferation of cells. [¹¹C]NMS-E973 showed strong binding to B16.F10 melanoma cells, which was inhibited by 200 µM of PU-H71, a non-structurally related HSP90 inhibitor. HSP90-specific binding was observed by in vitro autoradiography of murine B16.F10 melanoma, LNCaP and PC3 prostate cancer and SKOV-3 ovary carcinoma tissue slices. Further, B16.F10 melanoma-inoculated mice were subjected to a µPET study, where the tracer showed fast and persistent tumour uptake. Pretreatment of B16.F10 melanoma mice with PU-H71 or Ganetespib (50 mg/kg) completely blocked tumour accumulation of [¹¹C]NMS-E973 and confirmed in vivo HSP90 binding specificity. HSP90-specific binding of [¹¹C]NMS-E973 was observed in blood, lungs and spleen of tumour-bearing animals but not in control animals.

Conclusion: [¹¹C]NMS-E973 is a PET tracer for in vivo visualisation of tumour HSP90 expression and can potentially be used for quantification of HSP90 occupancy. Further translational evaluation of [¹¹C]NMS-E973 is warranted.