Evidence-Based Review of Adipose Stem Cell Therapy in Cancer Reconstruction

Purpose:

The use of adipose stem cells (ASCs) in autologous fat transfers is a favorable technology for reconstruction given their unique ability for self-renewal, unlimited proliferation, and pro-angiogenic and immunomodulatory properties.  However, much of the growing enthusiasm has been tempered by studies demonstrating a possible increased risk of growth and metastasis in cancer.  We present a systematic review of the literature evaluating the safety of ASC therapy in cancer patients.

Methods:

A systematic literature review was performed in December 2012 independently by two authors.   PubMed/MEDLINE, Ovid and other relevant plastic surgery databases were searched using the following terms: adipose AND ("stem cells" OR ("stem" AND "cells") OR "stem cells" AND ("tumour" OR "neoplasms" OR "tumor") AND ("disease progression").  We identified all relevant in vivo studies and the bibliographies of these articles were cross-referenced.

Summary of Results:

Ten in vivo studies examined the role of ASCs on tumor growth and proliferation.  The studies utilized variable ASC preparations, sources, doses, and delivery methods in different types of tumor models (tables 1 & 2).  Seven of these studies demonstrated pro-tumor effects of ASCs, two studies showed anti-tumor effects and one study demonstrated no change.  The main proposed mechanisms for enhanced tumorigenesis included increased tumor stroma formation and neovascularization.^{1, 2, 3} Various in vivo tumor models were used including breast (4), prostate (2), lung, pancreas, brain, and leukemia cells.   In all studies except one, ASCs were isolated from human tissue (abdominoplasty, mammoplasty, etc).  There was no significant relationship between the tumor model, source or type of ASC preparation and effect on tumor formation.   Notably, the two studies demonstrating anti-tumor effects introduced the ASCs several weeks after tumor engraftment while all of the pro-tumor studies co-injected the ASCs with the tumor cells suggesting that timing of delivery may be critical in determining the anti- or pro-tumor fate of these cells.^{4, 5}

Conclusions:

While ASCs have enormous potential in regenerative medicine, there is no clear consensus on the effect of ASCs on tumor growth.  Until sufficient evidence can be obtained, the greatest caution must be exercised before the widespread use of ASC technology in an oncologic patient setting.