Adeno-associated virus type 2 infection of nude mouse human breast cancer xenograft induces necrotic death and inhibits tumor growth

Adeno-Associated Virus Vector Design-Moving the Adeno-Associated Virus to a Bioengineered Therapeutic Nanoparticle

Although the number of market-approved gene therapies is still low, this new class of therapeutics has become an integral part of modern medicine. The success and safety of gene therapy depend on the vectors used to deliver the therapeutic material. Adeno-associated virus (AAV) vectors have emerged as the most frequently used delivery system for in vivo gene therapy. This success was achieved with first-generation vectors, using capsids derived from natural AAV serotypes. Their broad tropism, the high seroprevalence for many of the AAV serotypes in the human population, and the high vector doses needed to transduce a sufficient number of therapy-relevant target cells are challenges that are addressed by engineering the capsid and the vector genome, improving the efficacy of these biological nanoparticles.

Harnessing the Natural Biology of Adeno-Associated Virus to Enhance the Efficacy of Cancer Gene Therapy

Adeno-associated virus (AAV) was first characterized as small “defective” contaminant particles in a simian adenovirus preparation in 1965. Since then, a recombinant platform of AAV (rAAV) has become one of the leading candidates for gene therapy applications resulting in two FDA-approved treatments for rare monogenic diseases and many more currently in various phases of the pharmaceutical development pipeline. Herein, we summarize rAAV approaches for the treatment of diverse types of cancers and highlight the natural anti-oncogenic effects of wild-type AAV (wtAAV), including interactions with the cellular host machinery, that are of relevance to enhance current treatment strategies for cancer.

The regulatory role of Annexin 3 in a nude mouse bearing a subcutaneous xenograft of MDA-MB-231 human breast carcinoma

The following study investigated the effects of Annexin A3 (ANXA3) on breast cancer biological behavior in vivo, using nude mouse model bearing a subcutaneous tumor. A total of 18 female nude mice were randomly divided into three groups (n = 6): negative control group which was inoculated with MDA-MB-231 cells, blank control group which was inoculated with MDA-MB-231-NC cells, and the transfection group which was inoculated with MDA-MB-231-Sh cells. The experiment lasted for 4 weeks, during which mice conditions, diet and defecation were monitored on a daily basis. Body weight, as well as tumor diameters, which were assessed using standard caliper method, were measured once a week. In vivo imaging was performed to detect the activity of transplanted tumors. H&E staining was used to analyze the histological structure of tumor tissues in three groups, while flow cytometry and fluorescent RT-PCR were performed to measure cell proliferation and the expression of ANXA3 mRNA. Briefly, significantly slower tumor growth and tumor activity were observed in the transfection group compared to negative and blank controls, while the tumor weight and volume in this group were also significantly lower compared to the other two groups (P < 0.01). Sparse tumor cells accompanied with massive fibrous connective tissue proliferation, and lower new blood vessels formation were observed in transfection group compared to other groups. Moreover, mRNA and protein levels of ANXA3 were significantly lower in transfection group compared to the other two groups (P < 0.01). In addition, lower proliferation index and higher G_0/1 cell count were observed in transfection group compared to negative and blank controls (P < 0.01). To sum up, these results suggested that ANXA3 silencing regulates the proliferation and inhibits the growth of MDA-MB-231 breast cancer cells. Consequently, ANXA3 might be used as a potential target for gene therapy in breast cancer.

Adeno-associated virus type 2-mediated gene transfer of a short hairpin-RNA targeting human IGFBP-2 suppresses the proliferation and invasion of MDA-MB-468 cells

Adeno-associated virus 2 (AAV2) is prepotent in the biological treatment of breast tumor because of its low pathogenicity and immunogenicity. Our previous study demonstrated that insulin‑like growth factor‑binding protein 2 (IGFBP‑2) was highly expressed in patients with breast metastasis. In the present study, the effects of recombinant AAV2 on the growth and metastasis of breast cancer cells were determined in vitro, and in vivo. rAAV2-ZsGreen-shRNA-scramble and rAAV2‑ZsGreen‑shRNA‑hIGFBP‑2 were used to transfect MDA‑MB‑468, and MCF‑10A cells respectively, and observed that these virus could not penetrate the normal human breast epithelia MCF‑10A cell line. To investigate the effect of the recombinant virus on chemotherapeutics, paclitaxel was added to MDA‑MB‑468 cells and it was demonstrated that rAAV2‑ZsGreen‑shRNA‑hIGFBP-2-infected MDA-MB-468 cells were highly chemosensitive to paclitaxel compared with rAAV2‑ZsGreen‑shRNA‑scramble‑injected cells. In addition, it was demonstrated that the invasive ability of rAAV2‑ZsGreen‑shRNA‑hIGFBP‑2‑infected MDA-MB-468 cells was highly impaired compared with the rAAV2‑ZsGreen‑shRNA‑scramble group. In the nude mice xenografts, the rAAV2‑ZsGreen‑shRNA‑hIGFBP‑2 injection inhibited tumor growth and Ki‑67 expression was significantly downregulated compared with the scramble group. Following IGFBP‑2 knockdown using rAAV2-ZsGreen-shRNA-hIGFBP‑2, matrix metalloproteinase‑2 expression was significantly reduced in tumor tissues compared with that in rAAV2‑ZsGreen‑shRNA‑scramble treated tumor tissues. These findings have provided a direction for the application of novel AAV2‑based therapeutics for treating aggressive triple‑negative breast cancer types.

The use of nanoparticulates to treat breast cancer

Breast cancer is a major ongoing public health issue among women in both developing and developed countries. Significant progress has been made to improve the breast cancer treatment in the past decades. However, the current clinical approaches are invasive, of low specificity and can generate severe side effects. As a rapidly developing field, nanotechnology brings promising opportunities to human cancer diagnosis and treatment. The use of nanoparticulate-based platforms overcomes biological barriers and allows prolonged blood circulation time, simultaneous tumor targeting and enhanced accumulation of drugs in tumors. Currently available and clinically applicable innovative nanoparticulate-based systems for breast cancer nanotherapies are discussed in this review.

Identification of liver-specific enhancer-promoter activity in the 3' untranslated region of the wild-type AAV2 genome

Vectors based on adeno-associated virus type 2 (AAV2) are powerful tools for gene transfer and genome editing applications. The level of interest in this system has recently surged in response to reports of therapeutic efficacy in human clinical trials, most notably for those in patients with hemophilia B (ref. 3). Understandably, a recent report drawing an association between AAV2 integration events and human hepatocellular carcinoma (HCC) has generated controversy about the causal or incidental nature of this association and the implications for AAV vector safety. Here we describe and functionally characterize a previously unknown liver-specific enhancer-promoter element in the wild-type AAV2 genome that is found between the stop codon of the cap gene, which encodes proteins that form the capsid, and the right-hand inverted terminal repeat. This 124-nt sequence is within the 163-nt common insertion region of the AAV genome, which has been implicated in the dysregulation of known HCC driver genes and thus offers added insight into the possible link between AAV integration events and the multifactorial pathogenesis of HCC.

Adeno-Associated Virus 2-Mediated Hepatocellular Carcinoma is Very Rare in Korean Patients

BACKGROUND

The incidence and etiology of hepatocellular carcinoma (HCC) vary widely according to race and geographic regions. The insertional mutagenesis of adeno-associated virus 2 (AAV2) has recently been considered a new viral etiology of HCC. The aim of this study was to investigate the frequency and clinical characteristics of AAV2 in Korean patients with HCC.

METHODS

A total of 289 unrelated Korean patients with HCC, including 159 Hepatitis-B-related cases, 16 Hepatitis-C-related cases, and 114 viral serology-negative cases, who underwent surgery at the Samsung Medical Center in Korea from 2009 to 2014 were enrolled in this study. The presence of AAV2 in fresh-frozen tumor tissues was investigated by DNA PCR and Sanger sequencing. The clinical and pathological characteristics of AAV2-associated HCC in these patients were compared with previous findings in French patients.

RESULTS

The AAV2 detection rate in Korean patients (2/289) was very low compared with that in French patients (11/193). Similar to the French patients, the Korean patients with AAV2-related HCC showed no signs of liver cirrhosis. The Korean patients were younger than the French patients with the same AAV2-associated HCC; the ages at diagnosis of the two Korean patients were 47 and 39 yr, while the median age of the 11 French patients was 55 yr (range 43-90 yr).

CONCLUSIONS

AAV2-associated HCC was very rare in Korean patients with HCC. Despite a limited number of cases, this study is the first to report the clinical characteristics of Korean patients with AAV2-associated HCC. These findings suggest epidemiologic differences in viral hepatocarcinogenesis between Korean and European patients.

Novel delivery approaches for cancer therapeutics

Currently, a majority of cancer treatment strategies are based on the removal of tumor mass mainly by surgery. Chemical and physical treatments such as chemo- and radiotherapies have also made a major contribution in inhibiting rapid growth of malignant cells. Furthermore, these approaches are often combined to enhance therapeutic indices. It is widely known that surgery, chemo- and radiotherapy also inhibit normal cells growth. In addition, these treatment modalities are associated with severe side effects and high toxicity which in turn lead to low quality of life. This review encompasses novel strategies for more effective chemotherapeutic delivery aiming to generate better prognosis. Currently, cancer treatment is a highly dynamic field and significant advances are being made in the development of novel cancer treatment strategies. In contrast to conventional cancer therapeutics, novel approaches such as ligand or receptor based targeting, triggered release, intracellular drug targeting, gene delivery, cancer stem cell therapy, magnetic drug targeting and ultrasound-mediated drug delivery, have added new modalities for cancer treatment. These approaches have led to selective detection of malignant cells leading to their eradication with minimal side effects. Lowering multi-drug resistance and involving influx transportation in targeted drug delivery to cancer cells can also contribute significantly in the therapeutic interventions in cancer.