Have you been thinking of going on a diet but haven't found the right motivation yet? How about this one: fat feeds tumor cells and enhances their growth. And another question, for the ladies this time: have you ever wondered how those annoying love handles would look so much better inside a bra? No, I don't mean to put a bra around my waist, rather to move that bit of fat up to my chest . . .
Somehow the two things are related. Stay with me and I'll explain.
Numerous studies have shown that obesity not only increases cancer risk, but it's also linked to accelerated progression in numerous types of cancers. A group of researchers from the University of Texas Health Science Center at Houston investigated the reason for such poorer prognosis in obese patients. In a paper published in Cancer Research , Zhang et al. show that white adipose tissue (WAT) facilitates tumor growth in mice, and the association was independent of the mice's diet. To show this, instead of overfeeding the mouse to make it grow the fat tissue, they transplanted into the animals adipose stromal cells (ACS) -- cells that can be thought of as the "progenitors" of adipose cells. The transplanted cells increased the proliferation of white adipose tissue. Furthermore, once recruited into tumors, they increased tumor vascularization.
Tumors are basically an uncontrolled growth of cells. It takes a lot of resources to keep cells growing, and new blood vessels are created to "feed" the growth. Zhang et al. showed that the transplanted adipose cells were mobilized in the mouse model and promoted the creation of new blood vessels, thus effectively "feeding" the tumor and promoting its progression. Yuck, right?
"Our results indicate that obesity can accelerate tumor growth irrespective of concurrent diet. [. . .] Our data indicate that ASCs recruited by tumors become perivascular or differentiate into intratumoral adipocytes ."Why did I mention love handles and bras? Because Yoshimura et al. published a paper  in 2008 in which they do to humans what Zhang et al. did to mice. For a good reason, of course: in  Yoshimura et al. illustrate a new technique called cell-assisted lipotransfer in which they use the aforementioned ACS, the adipose progenitors, to perform cosmetic breast augmentation. Seems like a brilliant idea: no implants needed, no lipoinjection (which carries a high risk of necrosis), just isolate the fat cells, let them grow, then transfer them back. No scars, no complications.
"Final breast volume showed augmentation by 100 to 200 ml after a mean fat amount of 270 ml was injected. Postoperative atrophy of injected fat was minimal and did not change substantially after 2 months. Cyst formation or microcalcification was detected in four patients. Almost all the patients were satisfied with the soft and natural-appearing augmentation ."But now you see why this could present a potential problem: many breast cancer patients seek tissue regeneration after a mastectomy, and while Yoshimura's technique seems innovative and promising, Zhang et al. warn against its possible risks as the fat transfer could potentially feed remaining cancer cells and yield devastating results.
And the moral of the story is: go on a diet, get rid of the love handles, and be happy with a smaller size bra. ;-)
 Zhang, Y., Daquinag, A., Amaya-Manzanares, F., Sirin, O., Tseng, C., & Kolonin, M. (2012). Stromal Progenitor Cells from Endogenous Adipose Tissue Contribute to Pericytes and Adipocytes That Populate the Tumor Microenvironment Cancer Research, 72 (20), 5198-5208 DOI: 10.1158/0008-5472.CAN-12-0294
 Yoshimura, K., Sato, K., Aoi, N., Kurita, M., Hirohi, T., & Harii, K. (2007). Cell-Assisted Lipotransfer for Cosmetic Breast Augmentation: Supportive Use of Adipose-Derived Stem/Stromal Cells Aesthetic Plastic Surgery, 32 (1), 48-55 DOI: 10.1007/s00266-007-9019-4