Use of Vascular Endothelial Growth Factor-D As a Targeted Therapy in Lymphedema Treatment: A Comprehensive Literature Review

Introduction

It is estimated that 140–200 million people in the world are affected by lymphedema.^1,2 In developed nations, this condition is mainly associated with solid tumor treatments, and incidence can be as high as one in every six patients. Even though the disruption of lymphatic circulation is considered the initial trigger of lymphedema, the fact that patients often develop it months after the lymphatic injury demonstrates that inflammatory mechanisms play an active role in its pathophysiology.^3–5

Lymphedema is still considered incurable, so authors from different parts of the world have been interested in developing targeted therapies.^6–8 Two main research lines can be drawn regarding those targeted therapies: modulation of inflammation and tissue fibrosis,^9–11 and promotion of lymphangiogenesis through the delivery of vascular endothelial growth factors (VEGFs).^12–14

It is well known that VEGFs are responsible for mitosis and survival of endothelial cells in both embryonic and adult phases. ¹⁵ The already known VEGFs in mammals are VEGF-A, B, C, D, and placenta growth factor, and out of them, the ones who are more specific to lymphatic endothelial cells are VEGF-C and VEGF-D, acting through activation of vascular endothelial growth factor receptor 3 (VEGFR-3). ¹⁶

The VEGF-D capacity to activate lymphangiogenic receptors attracted attention as a therapeutic mechanism for lymphedema treatment. ¹⁷ Therefore, we conducted a systematic review of publications assessing its use as a targeted therapy in lymphedema treatment. We hypothesized that VEGF-D was a promising therapy to induce lymphangiogenesis in this medical condition.

Methods

Results

Study characteristics

Our search yielded 90 studies in the literature, but only 4 studies fulfilled the study eligibility criteria (Fig. 1; Table 1). Use of VEGF-D as a targeted therapy in lymphedema treatment was described only in experimental studies conducted in Finland (4/4). Three studies were conducted on small animals (mice), and one was in a larger animal (pig). The first publication was done by Tammela et al. in 2007. ¹⁸ All experiments used adenoviral gene transfer to induce expression of VEGF-D and other growth factors. VEGF-D expression was investigated in transplanted lymph nodes and skeletal muscle.

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FIG. 1.

Preferred reporting items for systematic reviews and meta-analyses diagram.

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Table 1.

Summary of the Studies

Author	Year	Country	Study type		Model	Delivery	Target	Growth factors		Key findings for VEGF-D
Tammela et al. 18	2007	Finland	Experimental	In vivo	Mice	Viral vector	LNT	VEGF-D	VEGF-C	—
Anisimov et al. 17	2009	Finland	Experimental	In vivo	Mice	Viral vector	Skeletal muscle	VEGF-D	VEGF-C	VEGF-D was less active than VEGF-C in stimulating VEGFR-3 and VEGFR-2
Lahteenvuo et al. 19	2011	Finland	Experimental	In vivo	Pigs	Viral vector	LNT	VEGF-D	VEGF-C	Lymphangiogenesis inferior than VEGF-C; seroma
Tervala et al. 20	2015	Finland	Experimental	In vivo	Mice	Viral vector	LNT	VEGF-D	VEGF-C; VEGF-C156S; VEGF-A	Lymphangiogenesis inferior than VEGF-C

LNT, lymph node transfer; VEGF, vascular endothelial growth factor; VEGFR, vascular endothelial growth factor receptor.

Authors evaluated the effects of VEGF-D in lymph node transfer, demonstrating its lymphangiogenic effect. Tammela et al. ¹⁸ performed a study on small animals (mice) using adenovirus to induce gene expression of VEGF-D and VEGF-C associated with lymph node transfer. Compared with control (LacZ-beta-galactosidase), both VEGF-D and VEGF-C promoted lymphangiogenesis. However, the effect of improving lymph node incorporation with the receptor lymphatic network was only described for VEGF-C in their article. ¹⁸ In a similar study, but on a larger animal (pig), Lahteenvuo et al. ¹⁹ expressed VEGF-D and VEGF-C on transplanted lymph nodes. They pointed out a higher lymphangiogenesis in animals treated with VEGF-C compared with those treated with VEGF-D. Interestingly, they observed that VEGF-D induced seroma, whereas VEGF-C did not. ¹⁹

Comparison of the effect on lymph node transfer of VEGF-D and other types of growth factor, such as VEGF-A, and VEGF-C156S was also studied. Tervala et al. ²⁰ in a study on small animals (mice) who underwent lymph node transfers, induced expression of VEGF-C, VEGF-D, VEGF-C156S, and VEGF-A genes using adenovirus. Compared with control, VEGF-D stimulated lymphangiogenesis and increased lymph node survival. However, they also noticed out that VEGF-C provided the greatest therapeutic results. ²⁰

Long-term effect of VEGF-D induced by adeno-associated virus in skeletal muscle cells was studied by Anisimov et al. ¹⁷ They conducted an experiment on small animals (mice) using adeno-associated gene transfer to express VEGF-D and VEGF-C in skeletal muscle cells, demonstrated that long-term expression of both growth factors improved lymphangiogenesis, generating functional lymphatic vessels. Interestingly, they noted that VEGF-D had a weaker activation action on VEGFR-2 and VEGFR-3, compared with VEGF-C. ¹⁷

Discussion

In this systematic literature review, we have shown that the scientific evidence about use of VEGF-D as a targeted therapy in lymphedema treatment has been summarized in only four experimental studies from Finland to date. Interestingly, all studies used viral gene transfer to induce expression of VEGF-D. Although all studies agreed regarding the lymphangiogenic potential of VEGF-D compared with controls, in studies that compared its effect with other growth factors it was noticed that VEGF-D had a lower lymphangiogenic effect compared with VEGF-C, and was found to induce seroma. ¹⁹ To our knowledge, this study is the first systematic literature review assessing the use of VEGF-D as a targeted therapy in lymphedema treatment.

VEGF-C and VEGF-D's capacity to stimulate receptors present in lymphatic and blood vessels (VEGFR-2 and VEGFR-3) is well established. ¹⁷ Therefore, it was not surprising that most of the studies on the topic investigated effects of both VEGF-D and VEGF-C in lymphedema treatment. However, translation lymphangiogenic growth factors into the clinic bring concerns about the risk of metastasis in patients with a past cancer history. ¹³ Studies have associated VEGF-D with metastasis and tumor growth, as well as worse patient outcomes for some tumors.^21–23

All experiments with VEGF-D were performed through viral gene transfer due to the difficulty of expressing and purifying it in its bioactive form. ²⁴ VEGF-D is secreted by cells in an inactivated form with N- and C-terminals, flanking a central activate domain. Therefore, requesting a proprotein convertase to remove those terminals generates a bioactive dimer, which acts on VEGFR-2 and VEGFR. ²⁴

Interestingly, the experiments demonstrated that gene expression of VEGF-D induced a less effective lymphangiogenesis compared with gene expression of VEGF-C. Anisimov et al. ¹⁷ pointed out in that VEGF-D was weaker than VEGF-C in stimulating those receptors, which agreed with other studies about the interaction between VEGF-D and VEGFR-2.^15–17 Moreover, Lahteenvuo et al. ¹⁹ noticed in their experiment that VEGF-D induced seroma, whereas VEGF-C did not.

We recognize limitations in our study, typical to systematic reviews, such as the potential of bias in interpreting the information presented in each study. However, we believe that our systematic review reports a relevant summary of the scientific evidence about the use of VEGF-D as a targeted therapy in lymphedema treatment, therefore, supporting future experiments to advance the field. Although current evidence demonstrated that VEGF-C seems to be the preferred growth therapy to induce lymphangiogenesis, we incentivize further studies addressing the efficacy and safety of using VEGF-D in lymphedema treatment.

Conclusion

The publications assessing the use of VEGF-D as a targeted therapy in lymphedema treatment demonstrated that this growth factor has a great lymphangiogenic potential compared with control. However, the studies pointed out that VEGF-C was more effective and did not present undesirable effects such as edema associated with VEGF-D. Nonetheless, further studies are still necessary to investigate efficacy and safety of using VEGF-D in lymphedema treatment on patients.