Superparamagnetic iron oxide nanoparticles (SPIONs) conjugated with recombinant human epidermal growth factor (SPION–EGF) were studied as a potential agent for magnetic resonance imaging contrast enhancement of malignant brain tumors. Synthesized conjugates were characterized by transmission electron microscopy, dynamic light scattering, and nuclear magnetic resonance relaxometry. The interaction of SPION–EGF conjugates with cells was analyzed in a C6 glioma cell culture. The distribution of the nanoparticles and their accumulation in tumors were assessed by magnetic resonance imaging in an orthotopic model of C6 gliomas. SPION–EGF nanosuspensions had the properties of a negative contrast agent with high coefficients of relaxation efficiency. In vitro studies of SPION–EGF nanoparticles showed high intracellular incorporation and the absence of a toxic influence on C6 cell viability and proliferation. Intravenous administration of SPION–EGF conjugates in animals provided receptor-mediated targeted delivery across the blood–brain barrier and tumor retention of the nanoparticles; this was more efficient than with unconjugated SPIONs. The accumulation of conjugates in the glioma was revealed as hypotensive zones on T2-weighted images with a twofold reduction in T2 relaxation time in comparison to unconjugated SPIONs ( P <0.001). SPION–EGF conjugates provide targeted delivery and efficient magnetic resonance contrast enhancement of EGFR-overexpressing C6 gliomas.

The stress-inducible 72 kDa heat shock protein Hsp70 is known to be expressed on the membrane of highly aggressive tumor cells including high-grade gliomas, but not on the corresponding normal cells. Membrane Hsp70 (mHsp70) is rapidly internalized into tumor cells and thus targeting of mHsp70 might provide a promising strategy for theranostics. Superparamagnetic iron oxide nanoparticles (SPIONs) are contrast negative agents that are used for the detection of tumors with MRI. Herein, we conjugated the Hsp70-specific antibody (cmHsp70.1) which is known to recognize mHsp70 to superparamagnetic iron nanoparticles to assess tumor-specific targeting before and after ionizing irradiation. In vitro experiments demonstrated the selectivity of SPION-cmHsp70.1 conjugates to free and mHsp70 in different tumor cell types (C6 glioblastoma, K562 leukemia, HeLa cervix carcinoma) in a dose-dependent manner. High-resolution MRI (11 T) on T(2)-weighted images showed the retention of the conjugates in the C6 glioma model. Accumulation of SPION-cmHsp70.1 nanoparticles in the glioma resulted in a nearly 2-fold drop of T*(2) values in comparison to non-conjugated SPIONs. Biodistribution analysis using NLR-M(2) measurements showed a 7-fold increase in the tumor-to-background (normal brain) uptake ratio of SPION-cmHsp70.1 conjugates in glioma-bearing rats in comparison to SPIONs. This accumulation within Hsp70-positive glioma was further enhanced after a single dose (10 Gy) of ionizing radiation. Elevated accumulation of the magnetic conjugates in the tumor due to radiosensitization proves the combination of radiotherapy and application of Hsp70-targeted agents in brain tumors.

Chaperone Hsp70 can activate adaptive immunity suggesting its possible application as an antitumor vaccine. To assess the therapeutic capacity of Hsp70 we administered purified chaperone into a C6 glioblastoma brain tumor and explored the viability and tumor size as well as interferon gamma (IFNc) production and cytotoxicity of lymphocytes in the treated animals. Targeted intratumoral injection of Hsp70 resulted in its distribution within the area of glioblastoma, and caused significant inhibition of tumor progression as confirmed by magnetic resonance imaging. The delay in tumor growth corresponded to the prolonged survival of tumor-bearing animals of up to 31 days versus 20 days in control. Continuous administration of Hsp70 with an osmotic pump increased survival even further (39 days). Therapeutic efficacy was associated with infiltration to glioblastoma of NK cells (Ly-6c1) and T lymphocytes (CD31, CD41 and CD81) as well as with an increase in the activity of NK cells (granzyme B production) and CD81 T lymphocytes as shown by IFNc ELISPOT assay. Furthermore, we found that Hsp70 treatment caused concomitantly, with a tenfold elevated IFNc production, an increase in anti-C6 tumor cytotoxicity of lymphocytes. In conclusion, continuous intratumoral delivery of Hsp70 demonstrates high therapeutic potential and therefore could be applied in the treatment of glioblastoma.Multiform glioblastoma is the most aggressive and common primary brain tumor in adults 1 with an incidence rate of 7.3 cases per 100,000 persons per year.2 The standard treatment for newly diagnosed glioblastoma currently includes surgical resection followed by radiotherapy and chemotherapy using apoptosis-inducing factors such as temozolomide, which is actively used nowadays. 3During the last two decades, increasing evidence has demonstrated that the high immunomodulatory potency of heat shock protein 70 (Hsp70) is due to its ability to specifically bind tumor antigens and present them to dendritic antigenpresenting cells (APCs).4 Several anticancer and antivirus vaccines were created based on Hsp70 chaperone. First, immunization of mice bearing tumors with Hsp70-secreting murine ovarian cancer cells caused a strong anticancer effect concomitantly with the elicitation of CD41 and CD81 Tand NK-cell activity.5 Another chaperonic vaccine contains fusion products of Hsp70 with Herpes virus VP22 peptide (aa268-301) that facilitate intracellular transport; this construct was effective in inducing a specific cytotoxic response against mouse lymphoma cells.6 Third, Ito et al. showed that the combined intratumoral delivery of pure Hsp70 with heating magnetic particles can efficiently destroy mouse melanoma B16 in a therapeutic modality. 7 More recently, we reported that the application of purified Hsp70 onto skin area covering B16/F10 melanoma significantly inhibited tumor progression and increased the survival of animals. 8Although the mechanism of antitumor activity of Hsp70 remains unclear, it is believed that the chaperone can trigger both innate and ...

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The study demonstrated that Hsp70-SPION conjugate intravenously administered in C6 glioma model accumulated in the tumors and enhanced the contrast of their MR images.